Robert Stewart, M.D. Answers Questions On: Amniocentesis

An amniocentesis is generally performed to diagnose a fetal chromosome abnormality, such as Down syndrome, Trisomy 13, or Trisomy 18. Often it’s performed after a woman has an abnormal screening test.

Amniocentesis is considered a diagnostic test, so it’s the definitive answer. We also offer amniocentesis for women whose fetus has a birth defect to see if that defect is related to a chromosomal or gene abnormality.

The risks of the procedure are the possibility of preterm labor; the possibility that the amniotic fluid, or the bag around the baby, can break or start leaking fluid; bleeding; the possibility of infection at the site where we put the needle in; and the possibility of hitting the placenta or the baby. But these risks are small.

We do amniocentesis with ultrasound guidance, so we watch the needle the entire way and can see where it’s going. There is a small risk of stillbirth, but that risk is around half a percent or less.

The benefits are that we know exactly what’s going on with the baby. We can give you a definitive diagnosis about the baby’s condition, if he or she has one, and that allows the family an opportunity to make plans. In cases where there’s a birth defect, it may offer us additional information regarding how to treat the baby. And, a lot of times, it puts the family’s mind at ease.

There’s nothing they need to do physically to prepare for the procedure. It’s a short procedure. To help them mentally prepare, I counsel patients beforehand to help them understand what the possibilities are and to help them prepare for whatever the results may be.