First Trimester Screening

First trimester screening is a test performed between 11 and 13 weeks' gestation. The test involves an ultrasound examination and/or a special test of maternal blood to screen for certain birth defects. By measuring the amount of fluid at the back of the baby's neck through ultrasound examination and/or by measuring the amount of two chemicals produced by the pregnancy that are present in maternal blood, a revised risk figure for Down syndrome and trisomy 18 are yielded.

It is important to remember that even though the first trimester screen may be "screen positive," this simply means that there is an increase risk for a condition. The majority of pregnancies with a "screen positive" result will result in a healthy baby. A genetic counselor will discuss your test results with you and review testing options of second trimester ultrasound, amniocentesis, and chorionic villus sampling (if the gestational age is appropriate).