Understanding Your Genetic Testing Options: Diagnostics

Doctors use several tests to help examine your unborn child's genetic makeup. Some of these tests examine the fetus' chromosomes, others use biochemical or DNA tests. These accurate tests can identify many (but not all) genetic birth defects.

How do you decide what tests are right for you and your baby? Speak with your doctor and learn as much as you can about these tests and which would benefit you. Here is a primer to get you started.

How Genetic Testing Works

New techniques in genetic testing allow doctors to acquire reliable specimens with little risk of injuring the fetus or mother. Tissue cells are obtained through a variety of procedures (the most common are listed within this article). The cells are then grown in the lab and stimulated to divide with chemicals. The chromosomes of dividing cells are isolated, stained, and examined.

The interpretation of these tests can occasionally be difficult. Genetics testing should be done by physicians and laboratories that have considerable experience with the available techniques.

Amniocentesis

What It Is: Babies normally float in a sea of amniotic fluid within the uterus. This fluid contains living fetal cells that have been released from the baby's skin and other tissues. Withdrawing fetal cell-containing amniotic fluid provides genetic material for examining your baby's chromosomes.

Other genetic and biochemical testing of the fluid is also possible. For example, measurement of acetylcholinesterase and amniotic fluid alpha-fetoprotein (AFP) can also be performed on amniotic fluid. These two tests assist in prenatally diagnosing spina bifida and other birth defects.

When It Is Performed:This procedure is usually done at 15 to 17 weeks gestation; results generally return in seven to 14 days.

The Risks:Amniocentesis is considered much safer today than previously thought. The advent of ultrasound use during this procedure is part of the credit, as it is now much easier for doctors to track where the amniocentesis needle is within a pregnant woman. However, there are still risks. According to the Centers for Disease Control and Prevention (CDC), the risk of losing your baby from amniocentesis is between one in 200 and one in 400, depending on the skill and experience of the doctor performing it.

You can lessens this risk by seeking out a doctor who's done the procedure many times (look for someone who performs amniocentesis tests at least 50 times per year) and also a doctor who uses ultrasound throughout the procedure.