twins and multiple pregnancy

Is this topic for you?

This topic is for women who are pregnant with more than one baby. It focuses on the questions that are specific to multiple pregnancies. For information on what to expect during pregnancy, labor, and childbirth, see the topic Pregnancy.

What is a multiple pregnancy?

A multiple pregnancy means that a woman has two or more babies in her uterus. These babies can come from the same egg or from different eggs.

Babies that come from the same egg are called identical. This happens when one egg is fertilized by one sperm. The fertilized egg then splits into two or moreembryos. Experts think that this happens by chance. It isn't related to your age, race, or family history.

If the babies you're carrying are identical, they:

• Are either all boys or all girls.
• All have the same blood type.
• Probably will have the same body type and the same color skin, hair, and eyes. But they won't always look exactly the same. They also won't have the same fingerprints.

Babies that come from different eggs are called fraternal. This happens when two or more eggs are fertilized by different sperm. Fraternal babies tend to run in families. This means that if anyone in your family has had fraternal babies, you're more likely to have them too.

If the babies you're carrying are fraternal, they:

• Can be both boys and girls.
• Can have different blood types.
• May look different from each other or may look the same, as some brothers and sisters do.

See a picture of identical and fraternal babies in the uterus.

What causes a multiple pregnancy?

If you take fertility drugs or have in vitro fertilization to help you get pregnant, you're more likely to have a multiple pregnancy.

Fertility drugs help your body make several eggs at a time. This increases the chance that more than one of your eggs will be fertilized. When in vitro fertilizationis used to help a woman get pregnant, the doctor may put several fertilized eggs in the uterus to increase the chances of having at least one baby. But this also makes a multiple pregnancy more likely.

You're also more likely to have more than one baby at a time if:

• You're age 35 or older.
• You're of African descent.
• You've had fraternal babies before.
• Anyone on your mom?s side of the family has had fraternal babies.
• You've just stopped using birth control pills.

What are the risks of a multiple pregnancy?

Any pregnancy has risks. But the chance of having serious problems increases with each baby you carry at the same time.

If you're pregnant with more than one baby, you may be more likely to:

• Develop a problem that causes your blood pressure to get too high (preeclampsia).
• Develop a type of diabetes that can occur while you're pregnant (gestational diabetes).
• Deliver your babies too early. When babies are born too early, their organs haven't had a chance to fully form. This can cause serious lung, brain, heart, and eye problems.
• Have a miscarriage. This means that you may lose one or more of your babies.
• Have a baby born with a birth defect that occurs when something is wrong with the genes or chromosomes. Certain genetic disorders may be more likely to occur in multiple pregnancies.