High Risk Pregnancy - Screening and Diagnostic Tests

At UAB we are pleased to offer first trimester screening and integrated first and second trimester screening for genetic disorders and birth defects as well as a Maternal Fetal Medicine specialist board certified in Genetics.

What are screening tests for birth defects?
Screening tests are performed at a specific time in pregnancy to determine whether a woman is at an increased risk of having a baby with certain birth defects such as Down syndrome, Trisomy 18, or neural tube defects. Screening tests DO NOT provide diagnoses. Screening tests can only determine if there is a chance of having an affected baby.

A negative test means that your child is at decreased risk of being affected, and further tests are not needed. A positive test means you are at increased risk of having an affected child, but a diagnostic test must be done to know for sure whether or not your child has one of these conditions. Although many women with an abnormal screening test will have a normal baby, only a diagnostic test can provide answers.

What are diagnostic tests for birth defects?
A diagnostic test provides a specific diagnosis. The diagnostic test for Down syndrome or Trisomy 18 is an analysis of the fetal chromosomes. It is performed on either cells isolated from the amniotic fluid via amniocenteses or from the placenta via chorionic villus sampling (CVS).
The diagnostic test for neural tube defects is a highly detailed ultrasound exam, and at times an amniocentesis is performed as well. As gestational age affects test results, an ultrasound is usually performed before any diagnostic testing to make sure your dates are correct and that you do not have a multiple gestation (twins). Which test is best depends on how far along you are in pregnancy.

Why should I consider having a screening test performed?
Currently, there is no proven effective treatment for neural tube defects or chromosome problems before the baby is born. However, if you learn early in your pregnancy that the baby will have one of these problems, you will have time to consider two options. You may begin to plan for the birth of a baby who may need intensive care after delivery, or you may decide to end the pregnancy. Having a screening test early in pregnancy gives you time to consider all of your options, and gives your doctor the chance to do everything possible to improve the outcome of your pregnancy.