A: The triple screen is a screening blood test that can be used for any pregnant woman, regardless of age, to help estimate the risk of certain fetal problems. It measures three hormones produced by the pregnancy: alpha-fetoprotein (AFP), estriol (E3) and human chorionic gonadotropin (hCG). The levels of these hormones change during pregnancy, and the test must be performed between 15 and 19 weeks of gestation for accuracy.

The results can only suggest whether you may be at increased risk of having a baby with a neural tube defect (e.g., spina bifida), Down syndrome or other chromosomal problems. An abnormal screening test result does NOT necessarily mean that your baby is affected: Fewer than four women out of 100 with a high result will actually have an affected fetus. Other reasons for abnormally high results include having a fetus that is younger or older than previously thought, having more than one fetus (twins) or having a placenta that is overly efficient at transporting these fetal hormones into your bloodstream. On the other hand, this test can help healthcare providers identify which seemingly normal pregnancies may benefit from additional testing.

“Negative” test results mean that the hormone levels are all normal for your pregnancy and no follow-up tests are indicated. A “positive” test result means that certain hormone levels are outside the normal range. If you have a “positive” test result, you will be offered additional tests, such as a detailed ultrasound, possibly a visit with a genetic counselor and an amniocentesis by an experienced physician.

Because you’re over 35, you may wish to have an amniocentesis to evaluate your baby’s chromosomes. The amniocentesis is far more accurate than the triple screen blood test and determines fetal chromosomes and the alpha-fetoprotein level in amniotic fluid. However, some patients are very hesitant to have an amniocentesis, which is invasive and carries greater risks than a blood test, and prefer to start with the triple screen test as an initial screen. These women will often use the results of the triple screen test to help them decide whether to undergo an amniocentesis. Please discuss your concerns with your healthcare provider during your first trimester so you have time to schedule whichever test you ultimately choose.