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A multiple gestation pregnancy is when a woman carries more than one fetus, and usually twins. The siblings may or may not be identical, depending on how many eggs the pregnancy involves.

In addition to the medical care and precautions that go with a single gestation pregnancy, special medical care may be necessary to monitor and manage any possible complications of a multiple gestation pregnancy.

This article looks at what to do if you have a multiple gestation pregnancy, how it might affect the pregnancy, any possible risks, and options for care and delivery.

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Twins can develop when one egg divides in two or when two sperm fertilize two eggs.

A multiple gestation pregnancy can happen in one of two ways:

  • One fertilized egg splits into two and forms two or more embryos.
  • Two or more sperm fertilize two or more eggs.

During in vitro fertilization (IVF), for example, a doctor will usually implant more than one egg into a woman's womb, because they will not expect all of them to be successful.,

Sometimes, however, more than one egg implants and develops successfully. In these cases, there will be a multiple gestation pregnancy.

Identical or not?

One of the first things many people wonder about a multiple gestation pregnancy is whether the infants will look the same.

Identical offspring: These will look exactly alike when they come from one fertilized egg that has split into two or multiple embryos.

Fraternal offspring: These are not identical but develop when two separate sperm fertilize two different eggs. The fetuses are not genetically identical.

Types

To find what type of pregnancy the babies are, a doctor will need to identify whether each fetus has its own chorion and amniotic sac.

The amniotic sac is a bag of fluid in the womb in which a fetus grows. Two membranes form the amniotic sac, and one of these is the chorion.

An ultrasound scan can show the pregnancy type, and doctors then classify twins into one of three categories:

Dichorionic-diamniotic: These may be fraternal or identical twins. They usually have their own placenta, chorion, and amniotic sac.

Monochorionic-diamniotic: These are identical twins that share a placenta and chorion but have their own amniotic sac. They can experience a complication known as twin-twin transfusion syndrome (TTTS). One twin "donates" blood to the other, resulting in one twin with too much blood and the other with too little.

Monochorionic-monoamniotic: Identical twins share a chorion, amniotic sac, and placenta. Complications can include problems with the umbilical cord.

There are noninvasive tests that can show whether twins are identical or fraternal from 9 weeks.

Who will have a multiple pregnancy?

Some women are more likely than others to have a multiple gestation pregnancy.

These include women who:

  • have had fertility treatment
  • are over the age of 35 years
  • have a family history of multiple gestation pregnancy

Women who have a multiple gestation pregnancy may notice:

  • very sore breasts
  • excessive hunger or rapid weight gain in the first trimester
  • severe morning sickness

These signs are more noticeable with twins than with a single fetus.

When developing babies start to move, the mother may also feel fetal movements at the same time in different areas.

Tests will show:

  • multiple fetal heartbeats
  • larger uterus than usual
  • more human chorionic gonadotrophin (hCG) and alpha-fetoprotein in the blood

A healthcare provider will confirm the presence of a multiple gestation pregnancy by performing an ultrasound exam.

Prenatal care

Some women who are experiencing a multiple gestation pregnancy may require more frequent health checkups, which may include regular ultrasounds.

Other women, especially those who have higher-risk pregnancies, may need to see a maternal-fetal medicine (MFM) specialist, which is a doctor who specializes in high-risk pregnancies, including multiples.

Diet and exercise can help the mother and the developing fetuses to stay healthy during pregnancy.

A mother should not be "eating for two," but they will need to eat more than usual. The ACOG recommend consuming an extra 300 calories each day per fetus.

There is no special diet to follow, but it is essential to eat healthful food, including:

  • plenty of fresh fruits and vegetables
  • whole grains
  • oily fish

Some foods, such as raw eggs, paté, and soft, mold-ripened cheese can be dangerous for the growing baby.

Find out more about what foods to eat and what ones to avoid in our dedicated article: Pregnancy diet: What to eat and what to avoid.

A doctor may recommend supplements, including:

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The Centers for Disease Control and Prevention (CDC) advise all women to take a multivitamin with folic acid. Folic acid is a B vitamin that encourages the healthy growth of the spine and brain.

Even before pregnancy, the CDC urge women who could become pregnant to make sure their diet includes 400 micrograms (mcg) of folic acid each day.

However, the University of Michigan suggest that women with multiple gestation pregnancies consume 1,000 mcg of folic acid every day.

It is essential always to speak to a doctor or midwife before taking any vitamins or other supplements, and to take them only as these professionals direct.

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Exercise is important during pregnancy.

People should discuss exercise options with a healthcare provider, as certain exercises may increase the risk of harm to the unborn child.

Yoga, swimming, and walking are safe options usually, but every pregnancy is unique, and these exercises may not be suitable for everyone.

Current guidelines for physical activity in the United States recommend getting 150 minutes a week of moderate-intensity exercise. It is preferable to spread this over several days, including during pregnancy and in the 12 months after giving birth.

Those who practice vigorous exercise before becoming pregnant can usually continue their exercise plan, but they should check first with a healthcare provider.

Sometimes, women experiencing a multiple pregnancy may need to reduce their levels of physical activity.

This may involve:

  • reducing exercise and other physical activity later in pregnancy
  • getting enough bed rest
  • decreasing travel or work activities

A doctor can advise on any necessary changes.

A woman who is carrying more than one fetus will gain more weight than a woman carrying a single baby during pregnancy.

The CDC recommend the following gains in weight for people who are carrying twins, depending on their weight or body mass index (BMI) before pregnancy:

Underweight before pregnancy (BMI below 18.5): Weight gain should be 50–62 pounds (lb).

Normal weight before pregnancy (BMI of 18.5–24.9): Weight gain should be 37–54 lb.

    Overweight before pregnancy (BMI of 25–29.9): Weight gain should be 31–50 lb.

    Obesity before pregnancy (BMI of 30 or more): Weight gain should be 25–42 lb.

    If a woman requests genetic testing during a multiple gestation pregnancy, it is important to note that some tests, using maternal blood, may be less sensitive than in single gestation pregnancies.

    However, newer blood tests are available that are suitable for twin pregnancies. In one small study, a specific test to identify Down syndrome showed promising results for use in twin pregnancies.

    Genetic tests, such as chorionic villus sampling (CVS) and amniocentesis may be more difficult and riskier in multiple pregnancies than with a single fetus.

    A genetic abnormality might affect one fetus but not the other, so the doctor will need to test both babies separately.

    In addition, some tests are invasive and can pose a risk to the pregnancy. The risk is greater in multiple gestation pregnancies than in a pregnancy when there is only one fetus.

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    Regular health checks during pregnancy can reduce the risk of complications.

    According to the American College of Obstetricians and Gynecologists (ACOG), multiple gestation pregnancies often result in higher rates of complication than single gestation pregnancies.

    One of the most frequent complications is preterm birth, which is any delivery occurring before 37 weeks.

    Some infants who are born preterm may experience health complications, including problems with:

    • breathing
    • eating
    • temperature control

    Some infants may also experience:

    • complications that lead to cerebral palsy, involving movement disorders
    • behavioral or learning problems, during both childhood and adulthood

    Some infants born at or before 32 weeks gestation might develop severe health conditions, some of which can be life-threatening.

    Some women carrying multiple fetuses may experience the following complications:

    There is a higher risk of these complications with a multiple gestation pregnancy than with a single one.

    In TTTS, blood from one fetus transfers to the other one. It affects 5 to 15 percent of identical twins, according to the National Organization for Rare Diseases (NORD). It is more likely to occur in identical twins than in other types of multiple pregnancy.

    Other possible fetal and newborn complications include:

    • spina bifida,
    • cerebral palsy
    • congenital heart anomalies
    • low birth weight, when an infant is born weighing below 5 lb 8 oz

    When there are two or more babies, one may be bigger and heavier than the other. This is sometimes a problem but not always.

    With multiple babies, a woman can give birth either through a vaginal or cesarean delivery. A cesarian delivery is most common, however.

    The mother can decide with her doctor on the best mode of delivery, based on a number of factors. These include:

    • the number of fetuses
    • position in the uterus
    • birth weight and health status
    • maternal health
    • progression of labor
    • complications
    • experience of the doctors

    Pregnancy can raise many questions, especially when it involves more than one fetus.

    Any woman who suspects she may be expecting more than one baby can gain more information by talking to her doctor or midwife.

    Q:

    What is the best way to prepare yourself for multiple gestations?

    A:

    As with all pregnancies, you can help prepare your body by closely following a nutritious diet, staying active, and discussing with your doctor any health conditions or medications you may be taking. Be sure to abstain from alcohol, tobacco, and recreational drugs.

    If you do find yourself expecting multiples, form good support systems with family members, close friends, or even other parents of multiples to help you once the infants arrive.

    Also, consider how having more than one infant may affect your work schedule and other obligations, and adjust accordingly.

    Holly Ernst, PA-C Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.