●Top 10 Things I Love About Having Twins
●Top 10 Unique and Unusual Types of Twins
●11 Things You Didn't Know About Twin Pregnancies
●Is It Twins? 10 Signs That You're Having Twins/Multiples
●The Risks of Pregnancy with Twins or Multiples
●Ten Things You've Always Wondered About Twins（Interesting Questions and Facts About Twins）
●Facts and FAQs About Identical Twins
Top 10 Things I Love About Having Twins
Being a parent twins or multiples is an experience full of ups and downs. There are many challenging times, for sure, but also plenty of moments where you feel so lucky and blessed to have them. These are some of the things that I love most about being a mom of twins.
1、Armfuls and Handfuls
Every child fills their parents' hearts and home with joy. That's what I really love about having twins or more. The love and joy are compounded. Cradling two twinfants in my arms was so incredibly, almost unbearably, sweet. Holding hands with two toddlers -- one on the right, and one on the left -- while crossing the street made me feel complete. Double hugs, double kisses, mommy-in-the-middle "sandwich" cuddles on the couch... life just doesn't get any better than that.
Parenting happens in stages. For people with a one-track mind, like me, it's much easier to manage two infants, two toddlers or two 'tweens, than to juggle the needs of a baby and a preschooler. The phases of parenthood are experienced more intensely, sometimes, because they are simultaneous, but I love it that way.
It's always exciting to see your child meet a milestone. But when two or more multiples accomplish their goals simultaneously, it's a wonderful experience for a family. For example, I was bursting with pride when both of my twins made honor roll on their last report cards, but the achievement was even sweeter because they were happy for each other.
It's such fun to hear them share jokes, call each other by nicknames and role play their special scenarios. Once when they were babies, 10 months old, we were driving down the road, when giggles erupted from the car seats in the back seat. As one laughed, the other broke out in giggles; they spurred each other on the entire ride home. What a sweet sound those baby giggles were; it is still sweet to hear them laugh together, not at each other, but with each other.
5、Alike, But Different
It's fascinating to be an observer of twins. With so many similarities, but such stark differences, it's always interesting to see how they develop as individuals. Where parents of singletons may say, "Oh, you are just like your sister was at that age," parents of multiples have an instant basis of comparison and contrast among their children.
Short and sweet .... one pregnancy = two babies! Such a deal! Although a pregnancy with multiples may have more risks, and sometimes more complications, it truly is a two-for-one deal.
7、A Sense of Status
Okay, I admit it. I get a little thrill of pride in being a mom of twins. It's like being a part of an elite club. You feel an instant bond with other parents of multiples. I love the reaction I get when I tell people I have twins. "Wow!" "I always wanted twins..." "I don't know how you do it..." It's almost like we enjoy an exclusive status in the parenting world, earning a slight nod of respect for pulling double duty.
Twins share everything -- their birthday, their parents' attention, and many of their belongings. Although they may get frustrated with their situation, as a parent, it's very gratifying to witness their "what's mine is yours" attitude in a moment of unselfish benevolence.
9、A Beautiful Bond
The twin bond is more enduring than any other relationship on earth, starting even before birth, and often outlasting many friendships and even marriages. Despite their squabbles, it's comforting to know that they will (hopefully) enjoy their unique relationship for all of their lives. As their mother, I feel really privileged to be a party to their special bond, and to have the opportunity to nurture it.
10、Confidence in Companionship
I love the confidence that my twins exhibit simply because they have always had each other to rely on. I love to watch them enter new, unfamiliar situations with total surety because they are together. I love seeing all the ways that being a twin shapes their personalities, both as an advantage and a disadvantage. They have never known loneliness because they've always had each other as a companion.
Top 10 Unique and Unusual Types of Twins
Most parents are familiar with the two classifications of twins - fraternal (dizygotic) and identical (monozygotic). Outside of those main classifications, there are some rare and interesting types of twinning.
Conjoined twins are monozygotic multiples that do not fully separate from each other due to the incomplete division of the fertilized ovum. The individuals will be connected at certain points of the body, and may share tissue, organs or limbs.
2、Twins Conceived Separately: Superfetation
Normally when an egg is fertilized, a woman's cycle is interrupted and ovulation ceases. Rarely, however, an egg can be released while a woman is already pregnant, resulting in twins that are conceived at different times.
3、Twins with Different Fathers: Heteropaternal Superfecundation
Fraternal (dizygotic) twins are the result of hyperovulation, the release of multiple eggs in a single cycle. Superfecundation describes a situation where the eggs are fertilized by sperm from separate incidences of sexual intercourse. In a case where a woman has sex with different partners, the twins could have different fathers and the apporpriate term is heteropaternal superfecundation.
4、"Half Identical" Twins: Polar Body Twins
There are two types of twins, right? Dizygotic (fraternal) twins result when two eggs are fertilied. Monozygotic (identical) twins come from a single fertilized egg that splits. But what if the egg splits and then each half meets a sperm? That's the proposed theory for polar body or "half-identical" twins, twins who are very much alike but aren't a 100% DNA match. Although it seems to be a reasonable theory, there is no definitive test to confirm polar body twinning.
5、Boy/Girl Identical (Monozygotic) Twins
Identical (monozygotic) twins are always same gender because they form from a single zygote that contains either male (XY) or female (XX) sex chromosome. However, there have been a few reported cases of a genetic mutation in male twins where one twin loses an Y chromosome and develops as a female. The female twin would be afflicted with Turner's Syndrome, characterized by short stature and lack of ovarian development. Of course, another explanation for gender differences in identical twins is an identical twin who undergoes a sex change operation.
6、Mirror Image Twins
Mirror image twins are monozygotic, twint that form from a single fertilized egg. When the split occurs late - more than a week after conception - the twins can develop reverse asymmetric features. This term is not really a type of twin, just an way to describe their physical features. For exmample, they may be right- and left-handed, have birthmarks on opposite sides of their body, or have hair whorls that swirl in opposite directions. In theory, if the twins faced each other, they would appear to be exact reflections of each other. About 25% of identical twins are mirror image twins.
A type of conjoined tiwns that develops asymmetrically, with a smaller, less formed twin dependent on the stronger, larger twin. Manar Maged gained notoriety after being featured on Oprah. A variation of parasitic twinning is fetus in fetu, where an abnormally formed mass of cells grows inside the body of its monozygotic twin. It survives during pregnancy, and even occasionally after birth, by tapping directly into the blood supply of the host twin. This report describes an Indian man whose fetus in fetu was discovered as an adult.
A type of twinning identified in a pair of three-year-old twins in 2007. Described as identical on the mother's side but sharing only half their father's genes, the rare twins developed when two sperm fertilized a single egg, which then split. One twin is a hermaphrodite being raised as a female, with both testicular and ovarian structures, while the other is anatomically male.
9、Twins with Different Birthdays
The most common explanation is a labor and delivery that begins before midnight on one day and ends after the clock changes to the next day. If that day happens at the end of the month, or even on New Year's Eve/Day, the two babies can have birthdays in different months and even different years! Also, sometimes a pregnancy is prolonged to provide each baby with an optimal chance for survival. If preterm labor forces the delivery of one baby, doctors can successfully control the abor and delay delivery to give the other baby more time in the womb. Twins and higher multiples have been born days and even weeks apart.
10、Twins of Different Races
Heteropaternal superfecundation can explain cases of fraternal (dizygotic) twins with differing racial characteristics. In one case, the differentiation was due to a lab mix-up during an in-vitro procedure. However, in 2005 in the United Kingdom, two bi-racial parents conceived fraternal (dizygotic) twin girl twins, Kian and Remee Hodgson. Described as a "one in a million" occurrence, experts explain that the girls inherited different genetic characteristics from their mixed race parents. One is fair-haired and light skinned, while the other has dark hair, eyes and skin.
Top 10 Ways to Increase Your Chances of Having Twins
Many people wonder what it takes to have twins, triplets or more. While having multiples is a gift and a blessing, there are some common factors that increase the chances of conceiving twins. Think you want to have twins or more? Here's how.
1、Have a History
Do twins run in your family? If you have a mother, brother, sister, uncle or long lost cousin with multiples, you may wonder if you'll have them too. Sometimes twinning is hereditary, it's true. However, only fraternal (dizygotic twins are influenced by heredity, and then only in some cases. If your mother or maternal grandmother was or had fraternal twins, you might have inherited a gene for hyperovulation, increasing your chances of conceiving twins also.
2、Grow or Gain Weight
A recent study published by the American College of Obstetrics and Gynecology correlates the rise in multiple birth rates with rising rates of obesity. Research found that mothers with a BMI (Body Mass Index) of 30 or higer were significantly more likely to have twins. Again, this statistic only holds true for fraternal (dizygotic) twins. The research also showed that women of above-average height were also more likely to have multiples.
3、Grow Up: Wait Until You're Older
Older mothers are more likely to conceive twins than their younger counterparts. It's thought that the body accelerates ovulation as the biological clock starts ticking faster. Seventeen percent of mothers over age 45 have multiples. Wait five more years and the odds rise to one in nine! However, the risks also increase; older mothers have a higher rate of miscarriage and are more likely to experience problems such as gestational diabetes during their pregnancy; in addition, their babies are at higher risk for chromosomal abnormalities.
4、Have More Twins
Once you have had a multiple pregnancy, you are significantly more likely to conceive -- and deliver -- twins again! Some estimates suggest that mothers of twins are four times more likely to have twins again than a woman who has never been pregnant, or who only had a singleton.
5、Diet: Yams & Dairy
No one is quite sure why, but the Yoruba tribe in West Africa has the highest rate of twinning in the world. A study concluded that the mother's diet was the cause, being high in cassava, a type of yam or sweet potato. The peelings of this vegetable are thought to contain a chemical that causes hyperovulation. In addition, a 2006 study found that women who consume dairy are five times as likely to have twins.
6、Seek Fertility Assistance
Reproductive technology has dramatically increased the multiple birth rate. Drugs that stimualate ovulation can lead to a multiple pregnancy, but multiples can also result from invitro fertilization. It's not just that multiple embryos are implanted in the mother, but there is also an unexplained increase in the number of monozygotic twins among IVF patients. No ethical doctor would provide treatment if it wasn't warranted, so fertility assistance should only be sought out when necessary.
7、Have A Big Family
The more kids you have, the more likely you are to conceive twins in a subsequent pregnancy. No one knows the magic limit that triggers a multiple pregnancy, so you'll just have to keep trying until it happens.
8、Conceive While Breastfeeding
Most people think that you can't get pregnant while breastfeeding, that the process of lactating keeps a woman from ovulating. However, plenty of mothers of twins can disprove that theory. Some research has supported the theory that the chance of twins or multiples is increased if a woman conceives while breastfeeding.
9、Get Pregnant On the Pill
Birth control pills are usually thought to be 99.9 percent effective at preventing pregnancy. However, that .01 percent often results in a double whammy -- multiples. Sometimes pregnancy occurs when the pill isn't taken consistently; in other cases, the hormonal mix of a particular drug type simply doesn't provide enough coverage to completely prevent ovulation. In either case, playing around with hormones can lead to hyperovulation, increasing the chances of multiples.
10、Just Get Lucky!
Many parents of multiples don't meet any of the classic criteria, yet find themselves doubly blessed. Monozygotic twins are particularly mysterious; no one is exactly certain what causes an egg to split after conception, producing identical twins. The bottom line is that there truly isn't a whole lot an individual can do to influence their chances of having twins; sometimes you just get lucky!
11 Things You Didn't Know About Twin Pregnancies
If you are expecting twins and don't know what to expect, you are not alone. Many women pregnant with twins have no idea what to expect, but that doesn't mean they -- and you -- can't learn. So here is some information to help you understand what's happening when you're expecting twins.
A twin pregnancy is a double blessing, but it can also carry greater risks than singleton pregnancies.
In the U.S, about three in every 100 pregnant women give birth to twins or triplets, according to the Mayo Clinic in Rochester, Minn.And by many accounts, twin pregnancies are on the rise.
Be prepared. Familiarize yourself with the top 11 things you didn't know about your twin pregnancy from conception through delivery.
1、You are more likely to become pregnant with twins naturally when you are in your 30s and 40s.
We all hear that the older we get, the harder it is to conceive, but advancing age may actually increase the likelihood of a twin pregnancy, says Abdulla Al-Khan, MD, the director and chief of maternal and fetal medicine and surgery at Hackensack University Medical Center in New Jersey. "Once you are 25 or into your 30s and 40s, ovulatory cycles are not regular anymore. If you are not regular and do ovulate, you could be ovulating two follicles at the same time." Voila! A twin pregnancy -- without assisted reproductive technologies.
2、If you have two buns in the oven, you may need extra folic acid.
Women pregnant with twins may need more folic acid to help stave off birth defects, says Manju Monga, MD, the Berel Held Professor and the division director of maternal-fetal medicine at the University of Texas Health Sciences Center in Houston.
"We recommend 1 milligram of folic acid per day for twin pregnancies and 0.4 milligrams for singleton pregnancies," says Monga, who has twins.Folic acid is known to reduce risk of neural tube birth defects such as spina bifida.
3、Women pregnant with twins clock in more time at the obstetrician.
Twin pregnancies require more monitoring than single pregnancies, Monga says. "We tend to do more frequent ultrasounds for growth in twin pregnancies, compared with one anatomy scan and one growth scan in a singleton pregnancy."
But along with additional testing comes risk. For example, the chance of miscarriage after amniocentesis is higher in twin pregnancies, Al-Khan says. "You are sticking the mother twice, so if the risk of miscarriage is one of 1,000 in singleton pregnancies, it would increase it to one in 500 for twins."
4、Morning sickness may be worse with twin pregnancies.
"One of the things that is postulated as causing morning sickness is high levels of human chorionic gonadotropin, and we know that levels of this hormone are higher in twin pregnancies, so women carrying twins have a higher incidence of nausea and vomiting in the first trimester," says Al-Khan. The good news? Most morning sickness abates within 12 to 14 weeks of pregnancy -- even in twin pregnancies.
That's not all, Monga says. Moms pregnant with twins complain of more back pain, sleeping difficulties, and heartburn than moms who are carrying one child. Moms pregnant with twins also have a higher rate of maternal anemia and a higher rate of postpartum hemorrhage (bleeding) after delivery.
5、Spotting may be more common during twin pregnancies.
"When you spot in the first trimester, you could be undergoing a miscarriage, and miscarriages are more common in mothers of twins, triplets, and quadruplets -- so we see more spotting in first trimester with multiples," Al-Khan says.
But a little spotting is no reason to hit the panic button even in twin pregnancies. "A little spotting in the absence of cramps is reassuring, but when you are cramping, passing clots, and actively bleeding, that is a sign that's something is happening and you should seek medical advice."
6、You don't feel the babies kicking any earlier with twin pregnancies.
"Generally when you are pregnant with twins, fetal movements become more noticeable at weeks 18 through 20 of pregnancy, and the same is true in singleton pregnancies," Al-Khan says. When a woman begins to feel fetal movements actually depends on whether she has been pregnant before. "If you have been pregnant before, you know what fetal movement is, but if you are pregnant for the first time, you really can't distinguish the movement from gastrointestinal activity."
7、Moms pregnant with twins may gain more weight than moms carrying one child.
"With twins, mothers gain more weight as there are two babies, two placentas, and more amniotic fluid," says Al-Khan. "You also need more calories for twin pregnancies."
Still, there is not a well-established formula for weight gain during twin pregnancies, says Monga. "The average weight gain is 25 pounds for singleton pregnancy and 30-35 pounds for twins. We don't want moms pregnant with twins to gain more than 40 [pounds] or less than 15 pounds."
8、Risk of developing gestational diabetes is higher in twin pregnancies.
"The gestational diabetes risk is higher in twin pregnancy," says Monga. That said, the biggest risk of gestational diabetes is having larger babies and requiring a C-section delivery, she says.
"While gestational diabetes is more common, the morbidity associated with it is less common because twin babies are not big babies."
Still, moms who develop gestational diabetes during pregnancy are more likely to develop type 2 diabetes later in life, she says.
9、Risk of preeclampsia during pregnancy is higher in twin pregnancies.
"People really don't know what causes preeclampsia to start, but we know it occurs more frequently in twin pregnancies," Monga says. Preeclampsia is marked by high blood pressure, protein in the urine, and sometimes swelling in the feet, legs, and hands. It is the precursor to the more serious, potentially fatal eclampsia.
10、Labor (and delivery) may come early with twin pregnancies.
Most moms carrying twins go into labor at 36 to 37 weeks, as opposed to 40 in a single pregnancy, Al-Khan says, and some may go even earlier. "Generally, if the twins are born after 34 weeks, there should not be a major concern, but a premature baby is still a premature baby," he says. "Twins are at higher risk of preterm labor and delivery and have higher degree of respiratory issues." As a result of being born too early, twins may be born at low birth weights, and such babies tend to have more health problems than babies born weighing more than 5.5 pounds.
Unfortunately, there is no evidence that bed rest alone prevents preterm labor or delivery in twin pregnancies, and the use of agents to stop preterm labor have not been proven to be effective either, he says. "Stopping premature labor is challenging in multiple gestations."
11、Cesarean section deliveries may be more common in twin pregnancies.
"The likelihood of having a C-section is absolutely higher in twin pregnancies," he says. "There is also a higher incidence of the baby being in breech position among twins than singletons." When the baby is in a breech position, a C-section delivery is usually required.
Is It Twins? 10 Signs That You're Having Twins/Multiples
Is it twins? Pregnant mothers often suspect that they are carrying more than one baby. Here are some of the most common signs of a twin or multiple pregnancy. Could you be having more than one? Check your symptoms against this list.
Seeing is believing... the only way to indisputably confirm a twin or multiple pregnancy is to see it -- via ultrasound. An ultrasound image can indicate without a doubt if there is more than one fetus. Ultimately, no matter what other signs or symptoms you have, the only way you'll know for sure is to have an ultrasound.
2、Doppler Heartbeat Count
Using harmless sound waves, a Doppler system amplifies fetal heart sounds, usually distinguishable late in the first trimester. An experienced physician or midwife can detect more than one heartbeat, indicating a multiple pregnancy. However, the sounds can be misleading; what appears to be a second heartbeat may actually be background noise or, rarely, the mother's own heartbeat.
3、Elevated HcG Levels
For various reasons, doctors may monitor HcG (human chorionic gonadotropin) levels. HcG is a hormone detectable in pregnant women's blood or urine about 10 days post-conception; it increases at a rapid rate, peaking about 10 weeks into the pregnancy. Twins may produce an elevated level of HcG. However, the standard HcG level for twins also falls within the normal range for singletons.
4、Abnormal AFP Test Results
AFP (Alphafetoprotein) screening is a blood test performed on pregnant mothers during the second trimester. Also known as maternal serum screening or triple marker screen, it is used to identify increased risks of certain birth defects. A twin pregnancy can produce an usually high -- or "positive -- result.
5、Measuring Large for Gestational Age
Throughout the pregnancy, the doctor or midwife may measure the height of the uterine fundus (from the top of the pubic bone to the top of the uterus) as a way of indicating gestational age. A twin or multiple pregnancy may causes the mother's uterus to expand beyond the range of a single pregnancy. However, other factors may also increase the measurements.
Just as a multiple pregnancy may cause a mother to measure large, it may also result in an increased weight gain. How much weight a woman gains can vary depending on her height, body type and how much she weighed pre-pregnancy. Increased or rapid weight gain more than likely reflects eating choices rather than twins; generally, mothers of twins only gain about 10 lbs. more than singleton mothers.
7、Excessive Morning Sickness
About 50% of pregnant women experience some amount of vomiting or nausea associated with their pregnancy. Moms of multiples certainly aren't exempt, but neither are they doomed to a double dose. Only about 15% of respondents in a poll on this site reported enhanced morning sickness symptoms as an indicator of their multiple pregnancies. Experiences vary widely -- some do, some don't.
8、Early/Frequent Fetal Movement
Feeling a baby -- or babies -- move inside the womb is one of the most thrilling aspects of pregnancy. Although many moms of multiples do experience more frequent or earlier fetal movement, there is considerable disagreement among medical professionals on the subject. For some women, recognizable feelings of movement occur earlier in subsequent pregnancies, whether there is one baby or more.
This is the most commonly reported complaint during pregnancy with multiples. Sleepiness, lethargy and exhaustion during the first trimester can be enhanced because the body is working overtime to nurture more than one baby. In some cases, the fatigue can be attributed to other factors (work, stress, poor nutrition, having other children), but it can also be an indication of multiples.
While the other items in this list refer to some kind of visible evidence -- exaggerated symptoms, abnormal test results, etc. -- we can't disregard the power of a mother's intuition. A family history of multiples, or a powerful hunch can be convincing indicators. Follow up with your doctor about these feelings.
The Risks of Pregnancy with Twins or Multiples
What are the real risks to mothers of multiples and their babies?
You've probably heard the term "high risk" associated with multiple pregnancy. It sounds threatening and scary, but don't let that dissuade you from educating yourself about the possible risks associated with having twins, triplets or more. Understanding the potential risks and complications, as well as the symptoms and treatment options, will make you better prepared to cope with the situation in the event you encounter problems in your pregnancy.
Some of the potential risks pose problems for the babies, while others impact the mother's health. Let's look at some of the risks for multiple babies:
1、Preterm Labor and Premature Birth
Perhaps the biggest risk associated with multiple birth is preterm labor, and consequently, premature birth. Mothers of multiples are twice as likely to experience preterm labor than their singleton peers. Preterm labor, the early onset of labor, can often be managed or even alleviated if the situation is addressed in a timely manner by medical professionals. Recognizing the signs of preterm labor is imperative.
Because of the increased potential for preterm labor and other complications, many twins and triplets, and nearly all quadruplets and higher order multiples are born prematurely. Prematurity impacts babies in a wide variety of ways, but fortunately, medical technology has advanced to a point where even the tiniest of babies can overcome the disadvantages of an early start in life.
* Signs of Preterm Labor
* The Consequences of Prematurity
2、Twin-to-Twin Transfusion Syndrome (TTTS)
Twin-to-Twin Transfusion Syndrome (TTTS) is a condition unique to monozygotic multiples that share a placenta. Blood vessels within the placenta become crossed, resulting in an unequal flow of blood betwen the babies. One baby essentially becomes a donor to the other, recipent baby. It's dangerous for both babies, but does not impact the mother's health. Recent technological advances give doctors the ability to correct the situation with a special surgical procedure using lasers. For more information on treating TTTS, visit the TTTS Foundation website.
* TTTS FAQ
3、Monoamnionic Monochorionic (Mo-Mo) Twins
Only a small percentage of twins are affected by this condition. It occurs when monozygotic twins are enclosed within a single amniotic sac. As the pregnancy progresss, their umbilical cords become entangled and compressed, cutting off the flow of nutrients and oxygen to their developing bodies.
Unfortunately, there is no cure for the situation except to deliver the babies. Generally, mothers of Mo-Mo twins require careful monitoring and possibly hospitalization.
More About MoMo Twins
Other conditions associated with multiple pregnancy impact the mother's health.
While some of the risks of multiple pregnancy only pose a danger to the babies, some conditions impact the mother's health. Aside from the physical strain and the emotional stress of carrying two, three or more babies, a mom of multiples may be susceptible to complications. In some cases, she may be at an increased risk for common complications of pregnancy, or she may experience more severe symptoms due to the additional babies.
Moms of multiples are more than twice as likely to experience gestational diabetes during their pregnancy with twins or more, probably because the increase in hormones produced by carrying an additional baby (or babies) interferes with their body's ability to process insulin. Often, it can be controlled with diet, but sometimes insulin must be administered. The condition does not pose a risk to the babies.
Whether there is a single, shared or multiple placentas, mothers of twins or more are at greater risk for complications such as placenta previa and placenta abruptio. Problems affecting the placenta can result in dangerous complications for the mother, including hemorrhage during pregnancy or after delivery. Fortunately, careful monitoring can detect most problems long before they pose a severe risk.
A recent Canadian study suggests some sobering information about the dangers of multiple birth. It found that women who carry two or more fetuses are thirteen times more likely to experience heart failure. Their risk of having a heart attack during pregnancy is nearly quadrupled. The researchers attributed the increase to physiological stress, explaining that each additional fetus raises the level of cardiac output.
It's not known how doctors will incorporate these recent research results into their treatment of multiple pregnancy.
7、Preeclampsia and PIH
Blood pressure problems plague many pregnant mothers of multiples. PIH, which stands for Pregnancy-Induced Hypertension, is diagnosed when a woman's blood pressure measures higher than 140 over 90. Your blood pressure should be checked regularly during your pregnancy; most medical caregivers take a reading at every office visit. Treatment options include restricted activity, bed rest, and occasionaly medications. Severe cases may require early delivery of the babies.
Elevated blood pressure is one component of a condition called preeclampsia. Preeclampsia differs from PIH when it is accompanied by proteinuria (protein in the urine).
Preeclampsia affects one in three moms of multiples during their pregnancy. In some cases it is treated with bedrest or medications, but should always be closely monitored becasue of the potential for serious complications like kidney failure, seizures or stroke. The condition is directly tied to pregnancy; if the babies are delivered, the preeclampsia goes away, usually without any lingering effects.
* Preeclampsia and Multiple Birth
Ten Things You've Always Wondered About Twins（Interesting Questions and Facts About Twins）
Twins are fascinating. They've been the subject of myth and mystery and a source of curiosity to many. Even those who know twins or have them in the family may have some questions about them. Have you ever wondered what causes twins or whether they have their own language? Explore the mysteries with these ten things that you've always wondered about twins.
1、Do Identical Twins Have Identical Fingerprints?
Twins have a lot in common. Identical twins even share the same DNA, for the most part. But does that include fingerprints?
Identical twins generate a lot of curiosity. And a lot of misconceptions! Parents of multiples have probably not given a great deal of thought to their childrens' fingerprint patterns, but the general public has spent a lot of time wondering about this topic.
So, do identical twins have identical fingerprints? The basic answer is NO. Identical -- or monozygotic -- twins form when a single fertilized egg splits in two after conception. Because they form from a single zygote, the two individuals will have the same genetic makeup. Their DNA is virtually indistinguishable.
However, fingerprints are not an entirely genetic characteristic. Scientists love to use this topic as an example of the old "nature vs. nurture" debate. Fingerprinting, along with other physical characteristics, is an example of a phenotype -- meaning that it is determined by the interaction of an indivdual's genes and the developmental environment in the uterus.
The ultimate shape of fingerprints are believed to be influenced by environmental factors during pregnancy, like nutrition, blood pressure, position in the womb and the growth rate of the fingers at the end of the first trimester. Thus, you will find similar patterns of whorls and ridges in the fingerprints of identical twins. But there will also be differences -- just as there are differences between the fingers on any individual's hands.
2、Can a Boy and a Girl be Identical Twins?
Every parent of twins faces the question. "Are your twins identical or fraternal?" The general public doesn't really understand exactly what the terms mean; if they did, they wouldn't ask whether a set of boy/girl twins are identical!
The short answer is No! The terms identical and fraternal don't describe what the twins look like, but actually how they form. Identical (monozygotic) twins are always of the same gender because they form from a single zygote that contains either male (XY) or female (XX) sex chromosomes. Therefore, boy/girl twins are always fraternal or (dizygotic); they can only form from two separate eggs that are fertilized by two separate sperm. Fraternal twins can be either two girls, two boys, or one of each.
Let's break it down further. Identical=monozygotic. Monozygotic means that the twins formed from a single fertilized egg that splits into two. It starts as one, splits into two. When it splits, it is either male or female. After it splits, there are either two males or two females.
Fraternal twins are dizygotic. Dizygotic = two zygotes. They are two separate eggs that are fertilized by separate sperm. The resulting egg/sperm combination can be male or female. The result is either two male twins, two female twins, or one male and one female.
●Two girl twins can be either identical or fraternal (monozygotic or dizygotic).
●Two boy twins can be either identical or fraternal (monozygotic or dizygotic).
●A set of boy/girl twins can only be fraternal (dizygotic). Boy/girl twins can not be identical (monozygotic).
However, there have been a few reported cases of a genetic mutation in monozygotic male twins. For some reason, after the zygote splits, one twin loses a Y chromosome and develops as a female. The female twin would be afflicted with Turner Syndrome, characterized by short stature and lack of ovarian development. It's extremely rare; less than ten cases have been confirmed. Given the odds, it's safe to assume that 99.9% of all boy/girl twins are fraternal.
Okay, One More Exception...
Of course, another explanation for gender differences in identical twins is an identical twin who undergoes a sex change operation.
3、Can Twins Read Each Other's Minds?
Twin Telepathy (Do twins have ESP?)
One of the magical mysteries associated with multiples is that they share a special connection beyond that of ordinary siblings. You'll often see them start to say the same thing at the same time. While the twin bond is a special aspect of their unique relationship, is it really endowed with extraordinary supernatural qualities (ESP)? Do they share the same thoughts -- or read each other's minds?
There is plenty of anecdotal data to support the idea. Nearly every set of twins can relate a story. Sometimes, one twin experiences a physical sensation of something that is happening to their twin (such as labor pains or a heart attack.) Other times they will find that they perform similar actions when they're apart, such as buying the same item, ordering the same meal in a restaurant, or picking up the phone to make a call at the exact same moment. They may appear to know the other's thoughts, by speaking simultaneously or finishing each other's sentences.
4、Can There be a Hidden Twin?
Every pregnant woman has a passing thought that perhaps there is more than one baby in there. Before ultrasound technology allowed a sneak peek inside the womb, twins were often a surprise to their parents. Despite the clarity of new technology, I receive emails every day from readers who suspect they are having twins, even when an ultrasound image only shows one baby. Are they right?
The only way to confirm a twin or multiple pregnancy is by visually identifying the multiple fetuses with ultrasound. If your doctor or caregiver can only see one baby, you're not having twins or multiples.
There are some very rare exceptions. Ultrasound provides a picture of the womb, but sometimes the picture can be misleading or misinterpreted, particularly if performed very early in the pregnancy or by an incompetent technician. After twenty weeks, a second fetus would be clearly visible on ultrasound, and the likelihood that there is another baby hidden in the womb is extremely minuscule.
Chances are, you are not having twins if there is no evidence of multiples on ultrasound. However, there are some rare exceptions, particularly when the ultrasound is performed in the first two months of pregnancy. For example, my first ultrasound, taken at seven weeks' gestation, clearly revealed one distinct embryo. Yet, my twenty week ultrasound clearly revealed two heads, four arms and four legs. Did another baby materialize along the way? No, not at all. Instead, the two-dimensional perspective of the first scan only caught a glimpse of one embryo. The other was shadowed - positioned directly behind the other -- and not visible from the view of the ultrasound tool, almost like an eclipse. This is likely because the girls were monochorionic, or contained in a single chorion (sac). Because they were positioned so closely together, their shadowed position could not be detected in a quick scan.
However, as I mentioned, there was no mistaking the presence of twins at my second ultrasound, at twenty weeks' gestation. Ultrasound performed later in the pregnancy is not likely to overlook a second fetus, or hidden twin. If you remain concerned that you are having undetected multiples, please discuss the issue further with your doctor or medical provider.
5、Do Twins Have Their Own Language?
Do twins have a secret language?
When my twins were toddlers, I'd observe them passing toys back and forth. As they'd accept the toy from the other, they'd respond "Aachee." Eventually, my husband and I adopted the term, and it became a family way of saying, "Thank you." Was it an example of twin talk? Or just baby babble?
One of the popular myths about mulitples is that they share a secret language, a form of communication known only to them. Terms such as idioglossia, autonomous language or cryptophasia describe the phenomenon of twin language, a fascinating concept that has intrigued researchers and parents alike. However, it's actually very rare for twins to develop a true "language," and usually only in cases of extreme isolation.
What is Twin Talk?
Rather, the phenomenon is actually attributable to young twins mimicking each other's attempts at language, often incorrectly. All babies babble incoherent sounds; it's their way of practicing vocalization and making the connections in their brain that lead to language development. However, twins may give the appearance that they actually understand each other's babbling ... thus the perception that they share a "secret language". As they grow up and repeat each other's vocalizations, it may appear that they are talking in a secret language, while they're really just mispronouncing sounds and words. About forty percent of twins, generally monozygotic or identical twins, will develop some form of autonomous language, using nicknames, gestures, abbreviations or terminology that they only use with each other. While parents and siblings can often discern the meaning, the twins generally don't use the terms with others.
Do your twins engage in twin talk? Share your story.
Language development in twins or multiples is often delayed or different from singleton peers. Some research shows that twins, particularly boys, may lag months behind in their ability to express themselves verbally. There are many factors that contribute to speech delays. Babies learn language from their caregivers, especially parents. Parents of multiples, who are often more exhausted and stressed by the challenges of caring for two or more babies, may be less verbally involved with their children. Young twins are together nearly all the time, and like any two people who spend most of their time together, they learn to rely on nonverbal or shorthand forms of communication. They're able to act intuitively, understanding each other's gestures, grunts or vocalizations. They also mimic each other's attempts at expressive language, often reinforcing incorrect pronunciation. Twins tend to talk faster and may abbreviate their words or leave out consonants as they pronounce words, perhaps in a competitive attempt to talk over their co-twin and grab their parent's attention first. Finally, some delays may result from cognitive or physical consequences of a premature birth.
In most cases, multiples will catch up to their singleton peers by the time they start school. But for some, speech problems can create difficulties for some children in later years, particularly in reading or spelling. In some cases, early intervention or speech therapy can help address special needs. For more information on speech delays, please refer to this article on identifying and resolving speech issues.
Tips for Parents of Twins
Although it's cute or interesting, parents of multiples should encourage correct speech in favor of twin talk. Here are some tips:
●Talk, talk, talk! Communicate with your babies, giving each child plenty of one-on-one time.
●Offer plenty of exposure to other children, particularly older children, instead of having young twins play together exclusively.
●Read to them. The benefits of reading to children are numerous.
●Motivate your multiples to express themselves with language. Don't give in to requests expressed by grunts or whimpers if they have the ability to make requests using words.
●Don't let one twin become a spokesperson for the other, Encourage each child to speak for themselves.
●Ask questions to engage your twins in conversation. As they get older, use open-ended questions to spark discussion.
●Don't interrupt your child to make corrections while they're speaking. Rather, let them finish, then say the words correctly by repeating them back to them.
6、If Identical Twins Have the Same DNA, Why Aren't They Exactly Alike?
Anyone who knows a set of identical twins knows that they are alike in many ways, but also very unique individuals. Why is that? Identical twins form from a single egg/sperm combination and share the same genes. While they often look very similar and have the same tastes and interests, they're also very different.
While identical twins form with the same set of genes, human development is not just genetic. The environment also has an impact. So, beginning in the early environment of the womb, external influences can change the appearance of twins. For example, some monozygotic twins share a placenta. One twin may have a more advantageous connection to the placenta, receiving the first run of nutrients. This situation can cause a size discrepancy between the babies, a physical difference that continues as they grow up. Twin-to-Twin Transfusion Syndrome (TTTS) is another condition that affects twins in the womb, and can impact their development.
While most twins grow up in the same home environment, there are many circumstances that create differences in the childrens' appearances, personalities, and interests. As the twins approach the teen years, they may even seek to establish dissimilar qualities in order to establish individual identities.
Scientists have offered a new explanation for the differences between identical twins. Epigenome refers to natural chemical modifications within a person's genome (genetic material). As an article in the New York Times explains, they "act on a gene like a gas pedal or a brake, marking it for higher or lower activity."
A study conducted by a team of researchers at the Spanish National Cancer Center in Madrid concluded that, while identical twins are born with the same epigenome, their epigentic profiles begin to diverge as they age. The differences increase as twins live longer and spend more time apart. The scientists offered two theories to explain this phenomenon. First, that epigentic marks are removed randomly as people age. Secondly, environmental influences change the pattern of epigentic marks.
In a Washington Post article Dr. Manel Esteller, lead researcher, said that "small epigenetic events before birth probably account for many of the minor distinguishing differences in the appearance, personality and general health of young twins."
The research is significant because changes in the epigenome may be responsible for the development of disease, like cancer. It's hoped that further study of the epigenome in identical twins will help researchers pinpoint factors that contribute to cancer.
Further Research: Not Actually Identical
A study published in the March 2008 issue of The American Journal of Human Genetics offers further explanation, even challenging the accepted notion that identical twins have identical genetic profiles. The research found changes in the DNA sequence between identical twins, reflected in Copy Number Variations (when a gene exists in multiple copies.) The researchdid not confirm whether these changes occur during fetal development or as twins age.
The research is significant because many medical conditions can be influenced by copy number variations, such as autism, AIDS, and lupus.
7、Can Twins Have Different Birthdays?
Twins, by definition, are two offspring born together, right? Yet, some twins blow out their candles on different days. Sometimes they celebrate their birthdays weeks or months apart, and in some cases, in different years!
Delayed Interval Births
In some cases, a delayed interval birth takes place when one multiple is delivered prematurely, but doctors are able to halt labor and keep the remaining multiple(s) in their mother's womb to grow and develop. Some of these multiples - twins, triplets or more - were born days, weeks or even months apart.
Close to Midnight
The difference between today and tomorrow is literally a matter of seconds. Plenty of babies are delivered in the middle of the night. So babies that are born close to midnight may arrive on different days. For example, Twin A may be born at 11:59 pm on one day while Twin B doesn't make an appearance until 12:01 am, which would be the next day.
This can create some interesting dilemmas. For example, Lexus and Amber Conway who were born either side of midnight on August 31st and September 1st. Unfortunately, September 1st is the cut-off date for starting school in their area, so only the first-born twin would turn five in time for the start of kindergarten.
Twins Born in Different Years
There have even been cases of twins born in different years. In 1991, Susan Goddeke went into labor on December 31st. She gave birth to baby Katherine at 11:56 pm, but baby Jessica wasn't born until 12:14 am ... on January 1st, 1992. A similar situation occurred in 2006-2007 in Boston to the Hoenig family.
As 2009 drew to a close, the Velasco family welcomed premature twins. Tiny Marcello Velasco was born in the last few seconds of 2009, then Stephano arrived just after midnight -- in 2010. The decade-divided duo were born ten weeks early and delivered by cesarean section.
To top it all, there are twins born in different millenia. Aaron and Luke Hegenberger are only eight minutes apart, but they were born in proximity to the turn of the millenium in 2000. Aaron arrived on New Year's Eve, 1999, just a few minutes shy of midnight. And in the first few seconds of the year 2000, his twin brother took his first breath.
8、Do Twins Run in Families?
Is There a Twin Gene? Do Twins Run in Families? Will I Have Twins?
Everyone knows someone who is a twin or has a twin. And there's a general assumption that twins run in families. Some families do seem to have clusters of multiples in their family tree. Is it coincidence? Or a genetic trait?
People are very curious about a family or genetic connection to twinning. I often get emails inquiring, "My grandmother's uncle was a twin. Will I have twins?" And when I tell people that I have twins, one of the first questions I'm asked is, "Do twins run in your family?" almost as if they aim to justify or explain my daughters existence as part of a historical pattern.
★Do Twins Run in Families?
There are plenty of families with multiple sets of multiples, for example, the Davis family of Frebericksburg, Virginia who have three sets of twins, or Eric and Elizabeth Hayes of New Jersey, parents of two sets of twins and sextuplets. There are also families who seem to have many sets of twins spread among generations, twin cousins and grandparents and nieces and nephews.
But do twins really run in families? Actually that's probably one of the most widely perpetuated myths about multiples. While some families do seem to have a preponderance of multiple births, it's often more than a coincidence than a connection.
★Is There a "Twin Gene"?
Of the factors that influence multiple birth, there is only one that could be identified as genetic or explained by family history: hyper ovulation. Hyper ovulation is the tendency to release multiple eggs during ovulation, increasing the chances of conceiving dizygotic (or fraternal) twins. So, in families where the women have a gene for hyper ovulation, genetics would sufficiently explain an increased presence of fraternal twins.
However, only women ovulate. So the connection is only valid on the mother's side of the family. While men can carry the gene and pass it on to their daughters, a family history of twins doesn't make them any more likely to have twins themselves.
Fraternal twins "run in families" on the mother's side only, if she inherits the gene for hyper ovulation.
★Do Twins Skip a Generation?
If your father was a twin, but you weren't, are you more likely to have twins? It's a common misconception that twins skip a generation in families. There is absolutely no evidence, other than circumstantial, that twins are more likely to occur every other generation. However, if you consider the influence of genetic hyper ovulation, this pattern could appear in families depending on whether their children were sons or daughters.
●Generation 1: Grandma
Grandma has the gene for hyperovulation. She & Grandpa have fraternal boy twins, Rob and Bob
●Generation 2: Rob & Bob
While Grandma's sons may carry the gene for hyperovulation, they do not ovulate. They will not have twins (excluding other factors). However, they each have a daughter.
●Generation 3: Molly & Polly
Molly and Polly, cousins, inherit the gene for hyperovulation from their fathers. They each have a set of twins.
You can see how this example makes it appear that twins skip a generation in families. The pattern is influenced by whether the inheritor of the hyper ovulation gene is male or female.
★What About Identical Twins?
Although theories and research abounds, there is no established connection between genetics and monozygotic (identical) twinning. Scientists haven't really identified and confirmed a clear cause for monozygotic twinning, which occurs when a fertilized egg splits and develops into two (or more) embryos. About ten years ago, I read about a theory that suggested that there was an enzyme in sperm that could cause an egg to split after fertilization, however I have not encountered any conclusions from that research. At this time, monozygotic twinning appears to be a random event, and all parents have a reasonably equal chance of conceiving identical twins.
Identical twins are random and do not run in families, except by coincidence.
★If I Have Twins in My Family, Will I Have Twins?
I don't have a crystal ball to know whether someone will have twins or not. If I did, I'd use it to play lottery numbers! If you have a family history of twins, and wonder whether you will have twins, consider these factors:
●What kind of twins are in the family?
Remember, monozygotic (identical) twins don't run in families; they're random. You may not know if your great-granduncles were identical or not; often there is no way to know for sure without DNA testing. However, twins that share a close physical resemblance are more likely to be monozyotic. Boy/girl twins are always fraternal (dizygotic).
●Are the twins a result of assisted reproduction?
In the last ten years, a large number of twin and multiple births can be attributed to fertility treatments: fertility drugs and invitro procedures. If your cousin had twins after taking Clomid, it has absolutely no impact on your chances of having twins.
●Whose side of the family had twins?
Let me talk to the women for a moment, since they are the ones who usually ask me if they'll have twins. If the twins are present on your husband's/partner's side, it won't influence your chances of having twins. Remember, the gene for hyperovulation is only a factor for the mother. If your mother -- or your grandmother or aunt -- was or had fraternal twins, then you might have the gene. But your husband's family history has absoultely no bearing on your own children, except maybe for the future possibility that you might have twin grandchildren!
●What other factors are at play?
Remember, a family history of twins is only one of many factors that influence multiple birth. Maternal age, race, weight, diet and reproductive history all contribute to twinning and may have a stronger influence than family history. Consult my resources on How to Have Twins to understand these other factors.
9、Can Twins Have Different Fathers?
Twins are defined as "...two young who are simultaneously born from one mother." (Encyclopedia Britannica). Note that the definition only refers to the mother. But what about fathers?
As technology has improved the accuracy and accessibility of genetic testing, it has become more evident that twins can have two different fathers. The situation only applies to fraternal (dizygotic) twins, not identical (monozygotic) twins, which form from a single egg/sperm combination.
However, fraternal twins are the result of hyperovulation, the release of multiple eggs in a single cycle. Superfecundation describes a situation where the eggs are fertilized by sperm from separate incidences of sexual intercourse. In a case where a woman has sex with different partners, the twins could have different fathers. The appropriate term to describe this situation is heteropaternal superfecundation.
This situation can also occur when twins are the result of fertility treatments, for example the case of Koen and Tuen Stuart, Dutch boys who were the result of IVF (in vitro fertilization). In a mixup at the lab, equipment had been used twice, causing another man’s sperm to be mixed with the father's.
10、What Causes Identical Twinning?
There are many known factors that increase the chances of fraternal multiples. In recent years, the multiple birth rate has risen dramatically and the increase has been attributed to many reasons, including fertility treatments, hormones in dairy products, and mothers who delay childbearing until they are older. Yet, the rate of identical twinning has remained steady, about 3 in 1,000 births. Identical -- or monozygotic -- twins form when a single zygote (egg/sperm combination) splits into two. Why would it do that?
Facts and FAQs About Identical Twins
★What are identical twins?
A general stereotype about identical twins is that they are clones. They act alike, look alike, and are expected to be "identical." However, the term identical twins actually refers to a type of twinning, and describes how they form, not what they look like.
The correct term for identical twinning is monozygotic. Monozygotic twins form from a single (mono) fertilized egg (zygote). The zygote splits into two parts after conception, resulting in the development of two individual embryos. Because the two embryos are the result of a single egg/sperm combination, they have the same genetic origins. They have the same DNA.
Dizygotic twins (often referred to as fraternal), are the result of two eggs fertilized by two separate sperm. Although most women only release a single egg in an ovulation cycle, sometimes multiples eggs are released. Dizygotic twins share about 50% of their genetic traits, the same as any other siblings born at different times.
★Some interesting facts about identical twins:
●The causes of monozygotic twinning are generally unknown and unidentified. No one really knows why an egg splits; technically it's a malfunction of the normal development process.
●There's no hereditary trait that influences a predisposition to having identical twins. Identical twins do not run in families. Although there are families with a high incidence of identical twins, it is due to chance, coincidence or plain good luck.
●Identical twins represent about a third of all twins. Dizygotic twins are twice as common as monozygotic.
●Birth rate statistics for identical twinning have remained stable over the years, despite the overall increase in twins and multiples since the late 1980's. The odds of having identical twins is about 3 in 1,000, whereas the birthrate for all twins is about 32.2 in 1,000.
●Identical twinning is not generally influenced by fertility-enhancing treatments like drugs or in vitro, although monozygotic twins have been produced in pregnancies that were the result of such treatments.
●Birth rates for identical twins are consistent across populations; it is the same regardless of race, geography or maternal age.
Frequently Asked Questions About Identical Twins
★What are semi-identical twins?
A new type of twinning was identified in 2007.
Definition: A type of twinning identified by scientists in a report in the Journal of Human Genetics in 2007. Described as identical on the mother's side but sharing only half their father's genes, the rare twins developed when two sperm fertilized a single egg, forming a triploid, which then split.
The twins, born in 2003 or 2004 in the United States, are described as somewhere between identical and fraternal. One twin is a hermaphrodite being raised as a female, with both testicular and ovarian structures, while the other is anatomically male.
Semi-identical twinning is distinguished from polar body twinning because the egg was fertilized by two sperm before splitting.
Also Known As: sesquizygotic, a term postulated by biologist Michael Golubovsky
★Are identical twins hereditary?
No. (See above)
★Why are identical twins different?
Despite their shared gene set, identical twins are unique individuals. No two individuals are exactly alike.
★Do identical twins always share a placenta during pregnancy?
No, this is a myth. Even many doctors will mistakenly identify twins as fraternal because there are two placentas. It depends on when the egg splits. If it is early enough, the two embryos will implant separately in the uterus and develop individual placentas. If the split occurs later, they may share a placenta.
★What are the medical concerns for identical twins in twin pregnancy?
Some types of monozygotic twins do experience conditions which put them at risk during pregnancy. Twins who share a placenta may be at risk for Twin-to-Twin Transfusion Syndrome. "Mo-Mo" twins (monochorionic / monoamnionic) are contained in a single amniotic sac, and their umbilical cords may become entangled and compressed.
★How can you tell if twins are identical or not?
You can't necessarily tell by looking. Although many identical twins share a physical resemblance, so do many dizygotic (fraternal) twins). Clues to zygosity can be revealed in many ways.
How To Determine if Your Twins are Fraternal or Identical
There are two basic categories of twins: Identical (or monozygotic) and Fraternal (or dizygotic). There are many reasons why it's important to determine twintype, but it's not always an obvious determination. Sometimes, asking a few simple questions can help parents evaluate their twins' zygosity and come to a conclusion as to whether they are identical or fraternal.
Time Required: Variable. Sometimes it's an instant determination and sometimes it can take months or years.
1. Are the twins males, females, or one of each? Monozygotic twins are always the same gender, except in rare cases where a chromosomal disorder is present. It can safely be assumed that boy/girl twins are dizygotic or fraternal.
2. Do the twins have the same bloodtype? Knowing your multiples' blood type can help determine zygosity. Monozygotic (identical) twins will have the same bloodtype. Dizygotic (fraternal) twins may have the same bloodtype, or they may have different types. Therefore, it may be concluded that twins with differing bloodtypes are dizygotic, or fraternal.
3. For multiples that were the result of in vitro fertilization, did the number of implanted embryos exceeds the number that were transferred? Occasionally, monozygotic multiples result after in vitro fertilization. If a single embryo is transferred, yet two embryos have implanted in the uterus, it can be assumed to be monozygotic twins.
4. How many placentas were present during pregnancy? Sometimes an analysis of the placenta can reveal zygosity. Information may be revealed with an ultrasound examination, or a physical analysis of after delivery. A single, shared placenta may indicate that the twins are monozygotic. The presence of two separate placentas, or two placentas that fuse together, is less conclusive. While all dizygotic multiples will have their own placentas (with very few exceptions), monozygotics may also have individual placentas, depending on when the zygote splits.
5. Were the twins diagnosed with TTTS while in the womb? TTTS (Twin to Twin Transfusion Syndrome) only effects monozygotic twins who share a circulatory connection in the placenta. Doctors have identified a few, rare cases of dizygotic twins who experienced TTTS, probably due to the reproductive technology used to conceive them. Twins diagnosed with TTTS are most likely monozygotic (identical).
6. Were the twins identified as monoamnionic in the womb? If so, they are monozygotic. Only monozygotic twins develop within a single, shared amnion.
7. Did you undergo prenatal testing that provided a comparable sample of DNA from each baby? It is possible that the results of prenatal testing such as amniocentesis can confirm the zygosity of the babies, so be sure to ask your doctor.
8. Do the twins share physical similarities? Individuals that look remarkably alike, with incredibly similar features, are more likely to be identical. However, appearance isn't a conclusive assessment of zygosity. Many dizygotic twins share similar characteristics (family resemblance) while many monozygotic twins don't look alike due to environmental influences.
9. If your answers to these questions are inconclusive, the only way to determine zygosity is with DNA testing. DNA testing is the most reliable way to confirm zygosity and know for sure. Companies like Affiliated Genetics and Proactive Genetics offer simple test kits for less than $200. If it's important for you to know, order a kit, follow the directions, and send in a sample for
1. It's important to truly understand the concept of zygosity. Identical twins aren't just two individuals that look alike. The accurate term is monozygotic, describing two individuals that result from a single egg-sperm combination that splits into two. Monozygotic multiples are similar because they share the same genetic origin. Fraternal twins are correctly described as dizygotic, the result of multiple egg-sperm combinations. Their genetic similarities are the same as any siblings. They may share a family resemblance, or they may look totally different.
2. Identical twins don't necessarily look alike. Even though they have genetic similarities, appearance is influenced by environmental conditions, even before birth. Identical twins may look remarkably similar due to their similar genetic makeup, or they may be different. There are many reasons why identical twins are different.
3. Ultrasound or placental analysis is often inconclusive. Don't rely on your doctor's assessment during pregnancy, as many wrongly conclude that babies are fraternal simply because there are two placentas. Follow up with DNA testing after the babies are born if you want to know for sure.
4. Besides curiosity, there are many reasons why parents of twins want to know their children's zygosity. It's nice to have an answer to the endless questions about twin type. But more importantly, the answer could have implications in medical situations.
5. If you can't afford to purchase a DNA test kit, you may be able to get tested for free by participating in a research study. For more information, check the links in the Research About Multiples resource collection. Or contact your local mothers of multiples organization or local research university.
★Do identical twins have identical fingerprints?
Many people wonder whether fingerprinting can be used to distinguish between two twins who look remarkably alike. Find out if identical twins have the same fingerprints.
★Can identical twins be different genders?
The short answer is no. Identical twins are either two girls or two boys. The longer answer is that there is a very rare exception to this rule that involves a chromosomal defect.
★Can there be identical triplets or higher order multiples?
★Do identical twins have ESP?
Many people believe that identical twins share a special connection, including the ability to read each other's minds.
★Do identical twins have their own secret language?
Twin talk? Or baby babble? Terms such as idioglossia, autonomous language or cryptophasia describe the phenomenon of twin language, a fascinating concept that has intrigued researchers and parents alike.