Screening tests

• Triple or quadruple (quad) blood tests. These tests check the amounts of three or four substances in a pregnant woman's blood. The triple screen checks the levels of alpha-fetoprotein protein (AFP), beta human chorionic gonadotropin (beta-hCG), and a type of estrogen (estriol, or uE3). The quad screen checks those three substances, plus the level of the hormone inhibin A. The doctor looks at these test results—along with your age and other factors—to find out the chance that your baby may have certain problems. Second-trimester tests can be done between 15 and 20 weeks of pregnancy. The triple and quad blood tests may be called the expanded AFP test, the AFP plus test, or the multiple marker screening test. Either of these tests may be done as the second part of the integrated screening test.
• Ultrasound. This test allows your doctor to see an image of your developing baby. It is often done at 18 to 20 weeks of pregnancy. Doctors can use ultrasound to look for certain features that are related to some problems, such as Down syndrome. The test also can be used to find problems of the heart, spine, belly, or other areas.

Diagnostic test

• Amniocentesis. Doctors use this test to look for chromosomal problems in the baby's cells. A doctor puts a needle through the belly and into the uterus to collect some of the amniotic fluid that surrounds the baby. This fluid contains some of the baby's cells. The test is done between 15 and 20 weeks of pregnancy, usually around week 16. This test also can help find neural tube defects, such as spina bifida.