Pregnancy and you blog

Prenatal genetic screening: Is it right for you?

By Mary M. Murry, R.N., C.N.M. January 7, 2012

When I was pregnant with my son more than 20 years ago, prenatal genetic screening was a relatively new thing — and the options were limited. Today, prenatal genetic screening for Down syndrome and certain other conditions has become standard practice. Prenatal genetic screening isn't required, however, and the results aren't conclusive. This might leave you wondering whether you should do one test, two tests — or perhaps no tests.

Start by considering how likely you are to have a baby with Down syndrome. Think about your age — since the risk of having a baby with Down syndrome is higher for older mothers — as well as your family history. If you're unsure, consult your health care provider or a genetic counselor.

Then consider what you'll do with the test results. Prenatal genetic screening tests — such as first trimester screening or the quad screen — involve a blood sample from the mother and, for first trimester screening, an ultrasound to measure the amount of fluid in the tissue at the back of the baby's neck. These tests don't pose any risks for your health or your baby's health. However, they can only tell you if the risk of Down syndrome or certain other conditions is higher than normal. They can't tell you with certainty if your baby does or doesn't have a chromosomal disorder. That requires invasive testing, such as amniocentesis or chorionic villus sampling — both of which carry a slight risk of pregnancy loss. A new blood test for Down syndrome is now available in some areas, but a positive result still requires confirmation by amniocentesis or chorionic villus sampling.

Before you agree to prenatal genetic screening, ask yourself some questions. How important is the reassurance of a negative or normal screening test? If the results of a screening test are positive or worrisome, will you choose a more invasive diagnostic test that carries a possibility of losing the baby? Would a firm diagnosis affect how you handle the pregnancy or prepare for the baby? If you opt out of further testing, how will you handle the uncertainty about your baby's health?

These are tough questions that demand serious thought. There's no right answer — only the answer that's right for you.

Jan. 07, 2012