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Tests You Need During Pregnancy

Prenatal tests are important for your health and your unborn baby's health. Here's what to expect.

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These tests are all routine and are performed on every pregnant woman, Petrikovsky says.

The next set of prenatal tests will be performed between weeks 8-18 of the pregnancy, Petrikovsky says, and will include an ultrasound screening, which can help determine your due date more accurately, and also look for abnormalities in the fetus. During this time, your doctor will also take other blood tests (known as a triple screen or a quad screen) that will measure blood levels of alpha-fetoprotein, estriol, hCG (human chorionic gonadotropin), and inhibin, which can indicate whether the fetus is at risk for abnormalities such as Down syndrome or spina bifida. A newer blood test, PAPPA (pregnancy-associated plasma protein A), conducted during weeks 10-14 of the pregnancy and used in conjunction with an ultrasound screening, is a good choice for women who are at risk of having a baby with a chromosomal abnormality, says Petrikovsky.

Depending on the results of the blood tests, the age of the mother (ages 35 and above), or the family history of the mother-to-be, the doctor may then suggest further prenatal tests, such as chorionic villus sampling (CVS) or amniocentesis, both of which detect Down syndrome or other abnormalities. CVS, which is usually done between weeks 10-12 of the pregnancy, can be performed either by passing a thin tube from the vagina into the cervix to remove a sample of tissue from the chorionic villi (which makes up the placenta), or by inserting a needle through the abdominal wall to obtain a tissue sample. Amniocentesis, which is performed between weeks 16-18 of the pregnancy, involves the insertion of a needle through the abdominal wall into the uterus, removing some of the amniotic fluid. Both CVS and amniocentesis carry a small risk of miscarriage.

Between weeks 24-28, you will be screened again for diabetes (some women develop pregnancy-related diabetes, known as gestational diabetes, which usually clears up after the baby is born), and patients who are Rh negative will be checked for Rh antibodies (which can be treated through a series of injections), says Petrikovsky.

At the end of the pregnancy, between weeks 32-36, you may be retested for syphilis and gonorrhea, as well as for group B strep (GBS), a type of bacterium that can cause meningitis or blood infections in newborn infants; if you test positive for GBS, you will be given antibiotics during labor and delivery to minimize the risk of transmitting the bacterium to your infant.

Though these are all routine tests, there may be other prenatal tests that your obstetrician will recommend, depending on your racial or ethnic background or family medical history, says Vivian Weinblatt, MS, CGC, regional manager of genetic services for Genzyme Genetics in Philadelphia and former president of the National Society of Genetic Counselors.

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