Prenatal Tests: A Chart of Who, When, and Why

by BabyZone Editors

Initial Laboratory Tests

Who Takes It?The PurposeRisk FactorMethod
After getting a positive result from an at-home pregnancy test, most women make an appointment with their OB-GYN to confirm pregnancy. Determine blood type and screening for anemia, Hepatitis B, and STDs. Pap smear tested for cancerous cells. Urine tested for protein and sugar levels. None Blood

Pap smear

Urine sample

CVS (Chorionic Villus Sampling)

Who Takes It?The PurposeRisk FactorMethod
Between 9-12 weeks. Women 35+, or those with an older child with birth defects or a family history of birth defects.To detect fetal genetic disorders, such as sickle cell disease and cystic fibrosis, and chromosomal abnormalities, such as Down syndrome. A slight risk of miscarriage and limb abnormalities. A tube is guided into the vagina and cervix, or a long needle is inserted through the belly into the placenta, under the guidance of an ultrasound. Cells are withdrawn from the placenta and tested in a lab to determine the child's genetic makeup.

Amniocentesis (Amnio)

Who Takes It?The PurposeRisk FactorMethod
Between 15-20 weeks. Women 35+, those with a family history of birth defects, as well as those with abnormal results in other prenatal tests. You and your doctor can discuss if this optional test is right for you.To determine the fetal genetic makeup, and test for Down syndrome, genetic disorders, spina bifida, and anencephaly (when the baby's brain and spine do not develop properly). A slight risk of miscarriage. Under the direction of an ultrasound, a long needle is inserted through the belly into the amniotic sac within the uterus to draw a sample of amniotic fluid. The sample is then sent to a lab for testing.

Maternal Serum Screening (AFP)

Who Takes It?The PurposeRisk FactorMethod
Between 15-20 weeks. Optional, but offered to all pregnant women.To indicate the woman's risk of delivering a child with Down syndrome, spina bifida, or anencephaly. None Blood is drawn and tested for levels of maternal serum alpha-fetoprotein and other pregnancy related substances.

Ultrasound

Who Takes It?The PurposeRisk FactorMethod
Between 16-20 weeks. This is up to your doctor's discretion, but most women are offered an ultrasound at this time. To check the fetal heart rate, diagnose a multiple pregnancy, or determine fetal age. Late in a pregnancy, ultrasounds screen for abnormalities, monitor high-risk pregnancies, and check the position of the fetus. None A device that emits sound waves is placed on the belly. The sound waves enter the body, bounce off internal tissues, and produce images of the fetus, placenta, and uterus on a television-like monitor.

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