Multiple Pregnancy: Twins or More - Exams and Tests

Most multiple pregnancies are now identified during the first or second trimester.

A 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 amniotic fluid.

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 human chorionic gonadotropin (hCG), the "pregnancy test" hormone, can be a sign of multiple pregnancy.

Tests used during a multiple pregnancy

Tests used to check for birth defects

Fetuses in multiple pregnancies have an increased risk of 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:

  • Chorionic villus sampling (CVS). It uses a tiny piece of the placenta, taken by passing a thin tube through your vagina and cervix and into the uterus. It can also be done through the abdomen with a needle. The sampling and genetic testing are done between 10 and 12 weeks of pregnancy.
  • 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 miscarriage 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 Birth Defects Testing.

WebMD Medical Reference from Healthwise
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