Prenatal Testing

Pregnancy is an exciting time, but it can also be challenging and full of decisions. Each clinic visit seems to hold new options, including options to learn about your baby's genetic health before he or she is born.

Some individuals decline all genetic screening and prenatal testing; this is a perfectly acceptable choice. Others choose a form of genetic screening to determine the chance that their baby might have a chromosome abnormality, like Down syndrome.

This can be done by either a first trimester screen or quad marker screen. The main difference between the two is when they take place. A first trimester screen will give you this information between weeks 11 and 14 of pregnancy; a quad marker screen usually doesn't take place until week 16.

A second-trimester ultrasound is also considered a prenatal screening test. Although it won't tell you details about the baby's genetic makeup, it will provide an assessment of the baby's anatomy to see if any birth defects exist. Since certain birth defects can be associated with genetic conditions, it may indirectly give you information about the chance that your baby has a genetic condition.

One of the main benefits of prenatal screening is that you can learn the chance that your baby has genetic condition without putting the pregnancy at risk; this is different than diagnostic testing. Diagnostic testing will give you a definitive answer about the baby's number and overall structure of chromosomal material, but carries with it a small risk for miscarriage.

Two options for diagnostic prenatal testing include amniocentesis and chorionic villus sampling (CVS). Amniocentesis is generally done after 14 weeks of pregnancy; CVS is done between weeks 10 and 12 of pregnancy. CVS is a slightly more invasive test, but provides the information at an earlier gestational age. However, it does carry a slightly higher risk for miscarriage than amniocentesis.

Meeting with a genetic counselor can be exceptionally helpful in making a decision about the best options to pursue, if any, during your pregnancy. One of the most important questions to ask yourself during this time is "What will you do with the information you learn?" Please, share your experiences and feedback for our readership