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A Guide to Fraternal Twins

There is nothing that compares to the feeling of having your pregnancy confirmed. You’re expecting a new member of the family and are probably filled with all kinds of emotions.

If your doctor told you that you’re expecting fraternal twins, you might feel overwhelmed. If you’re undergoing fertility treatments and want to increase your odds of having multiples, there are things you can do.

Many factors do play a big part in whether you’ll have multiples such as your family history, ethnic background, and if you take fertility medications.

Difference Between Identical and Fraternal Twins

Fraternal twins, or dizygotic, come from two different sperm cells and two different fertilized eggs. Identical twins, or monozygotic, develop from one egg that splits.

Since fraternal twins come from two separate eggs and sperm, they’ll usually develop two separate amniotic sacs and placentas. Identical twins are always the same gender, two boys or two girls and look nearly identical, while fraternal twins are sometimes different genders and look different.

The blood type of fraternal twins can be different while identical twins have the same blood type.

How Much Genetic Similarity Do Fraternal Twins Share?

Fraternal twins, genetically, are just like any brothers and sisters. They share 50 percent of their DNA, half of it coming from their mom and half coming from their dad.

Fraternal twins, just like non-twin brothers and sisters, can have similar qualities about them, but there isn’t an increased chance of that in fraternal twins.

It isn’t possible for fraternal twins to look exactly the same. It is possible for the egg to split very early on in the pregnancy resulting in two babies coming from one egg and two different sperm, leading to them being semi-identical.

Semi-identical twins are very rare and contain 50 percent of their DNA from their mom and 25 percent from their dad. Only one set of semi-identical twins has ever been confirmed.

Fraternal twins can look very similar to one another and that’s just because they have the same mom and dad, just like with non-twin siblings.

Chances of Having Fraternal Twins With IVF or IUI

The process itself of In Vitro Fertilization, or IVF, does not lead to an increased chance of having fraternal twins. Several years ago, doctors would implant multiple embryos in the uterus at one time to increase the chances of a successful pregnancy.

When this process occurred, the chances of having multiples increased. With modern technology, however, physicians now can implant only one embryo, decreasing the chance of multiples.

Women today can still elect to have more than one embryo implanted if they choose to. Some women will have multiple embryos implanted because they want multiples.

Intrauterine Insemination, or IUI, does not increase the chance of having fraternal twins. The chance of having fraternal twins with an IUI is around the same as without fertility treatments.

There is a chance of having multiples when you undergo the IUI procedure with a combination of fertility medications. The reason why fertility medications can have a big impact on whether you’ll have multiples is that they cause multiple eggs to develop at one time.

Fertility medications, such as Clomid, Femara, Gonadotropins, and Serophene, can increase the chances of having multiples by as much as 30 percent.

Other Factors That Can Increase the Odds of Having Fraternal Twins

There are many factors that can increase the odds of having fraternal twins including age. Women who are over the age of 30 can have an increased chance of multiples.

As you get older, your body produces more of a hormone called FSH, which is responsible for developing eggs in the ovaries.

Family history is another factor to take into consideration. This only works for fraternal twins, as having a family history of identical twins does not mean your chance of having fraternal twins increases.

Your odds of having a set of fraternal twins will be very high if your mom and dad both have a family history of fraternal twins.

Weight and height are other factors that can make it more likely for you to have multiples. Studies have shown that women that have a BMI of more than 30 percent have a better chance of conceiving fraternal twins.

A high BMI can lead your body to produce higher levels of estrogen, which can lead to your body releasing more than one egg. One study showed that taller women have a higher chance of multiples.

The reason for this is taller women contain more Insulin-like growth factor which helps increase ovulation.

Depending on your ethnic background, your chances of multiples might increase. Among all the ethnicities, African-American women have the best chance of fraternal twins.

The chance of having more than three fetuses is more common in Caucasian women over the age of 35 than any other ethnic background. Native Americans and Asians have the lowest twin rates.

There is also a chance that there is a connection between women that have just stopped taking oral contraceptives and fraternal twins. This is because oral contraceptives are a type of birth control that blocks ovulation to prevent pregnancy.

When a woman stops taking them, there’s a chance the ovaries release more than one egg.

Can Fraternal Twins Be Conceived on Different Days or by Different Fathers?

Fraternal twins can indeed by conceived on different days and/or by different fathers in a process called Superfecundation.

This process occurs when two separate eggs are released and fertilized during the same menstrual cycle and a woman has intercourse with two separate men within 5 days of ovulation.

Superfetation is when a second pregnancy occurs during two different ovulations, typically within a few weeks or sometimes months, after the first pregnancy. Each of these fraternal twins can have different fathers.

Superfetation is very rare and only has been reported multiple times. Eggs can only live up to 24 hours in the reproductive system, but sperm can live up to five days, making it possible to conceive twins by different fathers.

Risks Associated With Fraternal Twins

There are many risks associated with carrying fraternal twins, the biggest being preterm labor, meaning before you’ve hit your 37th week of pregnancy.

Most singular pregnancies will last around 39 weeks, while the average is 36 weeks if you’re carrying twins and 32 weeks if you have triplets. Approximately 60 percent of all twin births will result in preterm labor.

Another risk to carrying fraternal twins is preeclampsia. This condition causes high blood pressure and damage to the organ system, mainly the kidneys and liver, and can be fatal if left untreated.

While this condition is bad for mom, it’s also bad for baby. Preeclampsia can prevent the placenta from getting enough blood which can result in low birth weight and/or growth restriction.

Carrying multiples also makes you three times more likely to have a placental abruption than if you were carrying only one baby. This occurs when the placenta separates from the uterine lining, mainly during the third trimester.

Since the placenta is your baby’s life support system, this condition is very serious and requires immediate attention. Sometimes the placenta will only tear partially from the uterine lining, which results in bed rest until delivery.

In the event of a total separation, delivery is the only option because your baby needs the placenta for oxygen and nutrients.

Since carrying multiples come with risks, your doctor will closely monitor you and your babies during your pregnancy. The doctor will check the heart rate of your babies and their movement, and how much amniotic fluid your body has.

Even though you can’t eliminate all the risks associated with carrying twins, there are ways to minimize them for a healthier pregnancy. Make sure you see your doctor regularly, eat well, and stay hydrated.

You also shouldn’t put yourself on bed rest unless your doctor tells you this is necessary. Regular activity and exercise can lead to a healthier pregnancy.

Vanishing Twin Syndrome

A woman can go into the doctor for an early ultrasound and have the doctor confirm she is having multiples. Later in the pregnancy, the doctor may only be able to find one heartbeat, eventually confirming one of the fetuses is no longer there.

When a woman loses a fetus in the first trimester, there is a chance the fetal tissue is absorbed by the mother, placenta, or other fetus. You could experience symptoms related to a miscarriage including pelvic pain, vaginal bleeding, and cramping with Vanishing Twin Syndrome.

Statistics show that there is a 20 to 30 percent chance of Vanishing Twin Syndrome occurring during a pregnancy with multiples, more commonly with fraternal twins.

After the loss of one fetus occurs, chances are the pregnancy with the other baby will go on without complications, but your doctor will closely monitor you during the rest of the term.

Fraternal Twins and Birth Defects

Twins are more likely to have birth defects due to a variety of reasons, many stemming from preterm labor. Birth weight defects are common among fraternal twins due to being born before the end of the pregnancy term.

If the babies are born before 32 weeks and are smaller than 3.3 pounds, they may end up with long-term problems that can include mental retardation, cerebral palsy, blindness, and hearing loss.

Fraternal twins are also more likely to develop congenital heart defects, especially those conceived through IVF. Other birth defects include spina bifida, heart complications, and gastrointestinal abnormalities.

There is a 60 to 90 percent chance you’ll go into labor before 37 weeks, but if a doctor feels like it’s necessary, they can delay the birth for a few days while they give the baby corticosteroids that will help develop their lungs quicker.

The babies may also receive magnesium sulfate which is used to lower the chances of them developing cerebral palsy.

What to Expect With Fraternal Twins?

If you’re carrying fraternal twins, you’ll likely need to take extra folic acid to decrease the risk of your babies having birth defects. You’re also likely to get extra care from your doctor than if you were only carrying one baby.

This is because the doctor needs to keep a close eye on you as well as your babies and their development to ensure everyone is healthy. You’ll likely have more ultrasounds so the doctor can monitor the growth and development of the fetuses.

If you choose to undergo testing such as an amniocentesis, your chances of miscarriage will be higher.

Your morning sickness can be worse if you’re carrying fraternal twins than a single fetus because of the higher levels of human chorionic gonadotropin, or HCG.

You may also experience increased back pain, heartburn, and problems sleeping. Something else you might have during pregnancy with multiples is spotting.

Always let your doctor know if you have these symptoms so they can monitor you more closely if necessary.

Another thing you can expect when carrying more than one baby is more weight gain from having two placentas, two babies, and extra amniotic fluid. The average weight gain when carrying one baby is 25 pounds and 30-35 pounds for twins.

Your risk of developing gestational diabetes is higher during a pregnancy with multiples, which can affect your baby’s health and your pregnancy. If you’re pregnant, it’s important to start eating a healthier well-balanced diet.

If you were diagnosed with gestational diabetes, healthy foods in combination with exercise and taking medications regularly can help control your blood sugar.

There is also an increased risk of having a cesarean section with multiples. A C-Section isn’t always mandatory, especially if both babies are in the head-down position.

Since there can be multiple complications, you’ll need to have a doctor who is skilled in twin births to be there. Before you give birth, you might have to go into an operating room just in case an emergency c-section is needed.

Twins, whether fraternal or identical, can be a great blessing. However, these pregnancies do come with added risks to mother and baby.

Always be sure to follow your doctor’s advice, eat healthy and maintain an active lifestyle, as much as you can anyways!