Crucial Prenatal Testing

Pregnancy involves a lot of tests, but your doctor may not perform some crucial ones unless you ask. Three that you should bring up:

Test: Down syndrome screen

Why: The American College of Obstetricians and Gynecologists recently updated screening recommendations to include all pregnant women, not just those 35 and older.

What's involved: Depending on your medical history, options include a nuchal translucency test, which measures the thickness at the back of the fetus's neck during an ultrasound and is accompanied by blood tests that screen for chromosomal abnormalities; amniocentesis, in which amniotic fluid is tested; and chorionic villus sampling, which screens tissue from the placenta. The timing for these tests varies; ask your doctor.

Test: Fetal fibronectin (fFN)

Why: If you're at risk for preterm delivery or you're experiencing signs of labor, this test can rule out early delivery with 99 percent accuracy. Knowing that you won't give birth early may mean avoiding bed rest -- and needless worry, says Diane Ashton, M.D., deputy medical director at the March of Dimes.

What's involved: The doctor collects a sample of cervical secretions during an exam similar to a Pap smear and may follow up with an ultrasound. Depending on the results, he may repeat the test every two weeks.

Test: Group B Strep (GBS)

Why: This bacterium can pass to newborns during delivery, causing them to develop pneumonia, meningitis, a blood infection, or other complications. Previously, doctors screened only those women who were at risk for GBS. Now, all women should be screened, between 35 and 37 weeks.

What's involved: A swab of the vagina and rectum. If GBS is present, you'll get antibiotics at delivery.