Multiple Pregnancy: Twins or More

Most multiple pregnancies are now identified during the first or second Reference trimester Opens New Window.

A Reference fetal ultrasound can show whether there is more than one fetus in the uterus. If you have more than one fetus, you will have an ultrasound several times during the pregnancy to monitor fetal growth and Reference amniotic fluid Opens New Window.

Sometimes the first sign of a multiple pregnancy is from a test that was done for another reason. For example, a very high level of Reference human chorionic gonadotropin (hCG), the "pregnancy test" hormone, can be a sign of multiple pregnancy.

Tests used during a multiple pregnancy

• Blood pressure checks at every prenatal appointment are used to monitor you for high blood pressure or Reference preeclampsia Opens New Window.
• Blood testing is used to check you for low iron (Reference anemia Opens New Window). Anemia is a common problem for women with multiple pregnancy, because the fetuses use a great amount of the mother's iron stores.
• A Reference urine test and Reference urine culture can be used to screen you for a Reference urinary tract infection (UTI) Opens New Window.
• Reference Transvaginal ultrasound may be used to check the length of your cervix. A short cervix is a sign of an increased risk of Reference preterm labor Opens New Window.
• In the second trimester, you may have an Reference oral glucose screen Opens New Window to check for Reference gestational diabetes Opens New Window.
• Reference Electronic fetal heart monitoring may be used before or during delivery, to make sure the fetuses are doing well.

Tests used to check for birth defects

Fetuses in multiple pregnancies have an increased risk of Reference genetic disorders and birth defects.

There are two types of birth defects tests: screening and diagnostic.

Screening tests show the chance that a baby has a certain birth defect. But they can't tell you for sure that your baby has a problem. Some of the available screening tests for birth defects are not as accurate when used for women carrying more than one baby. Talk to your doctor about your options for screening tests.

Diagnostic tests show if a baby has a certain birth defect. Diagnostic test options may include:

• Reference Chorionic villus sampling (CVS). It uses a tiny piece of the Reference placenta Opens New Window, taken by passing a thin tube through your vagina and cervix and into the uterus. The sampling and genetic testing are done between 10 and 12 weeks of pregnancy.
• Reference Amniocentesis, which uses a small amount of amniotic fluid, taken by inserting a needle into your abdomen and uterus. The sampling and genetic testing are usually done between 15 and 20 weeks of pregnancy. (Amniocentesis is also sometimes used in the last trimester to see whether the fetuses' lungs are mature enough to breathe well after delivery.)

CVS and amniocentesis have the same slight Reference miscarriage Opens New Window risk when used to test a multiple pregnancy. You may want earlier CVS results if you have to make decisions about treating or continuing a pregnancy.

For more information, see the topic Reference Birth Defects Testing.

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