Early Genetic Testing in Pregnancy

Prenatal genetic testing is an option that any mother-to-be can either decline or pursue. Genetic disorders may be inherited from parent to child, but sometimes your family background has no bearing. Prenatal screenings can tell you if your baby is at risk for certain genetic disorders. Perhaps this is all the information you need to know. However, more invasive diagnostic tests give you more concrete information about your baby’s genetic makeup.

Reasons for Genetic Testing

You might want to consider genetic testing for various reasons while you’re still pregnant, but according to the American College of Obstetricians and Gynecologists (ACOG), there are certain factors that might sway you. If you are 35 or older, or if your baby’s father will be 50 when the child is born, you may want to consider diagnostic testing. A family history of inherited disorders–Down syndrome, Tay-Sachs disease, muscular dystrophy, cystic fibrosis or other genetic diseases, chromosomal disorders and birth defects–may warrant genetic testing. A medical professional called a genetic counselor can assist you in determining if your baby is at risk for a certain disorder.

Types of Screenings

Screenings are tests that tell you if your child is at risk for a certain disorder and often doesn’t look at any one condition, says the ACOG. They are not conclusive. A maternal serum screening is conducted between the 15th and 20th weeks of pregnancy and simply involves taking a blood test from the mother. This screening can tell you if your child is at risk for Down syndrome, trisomy 18 or neural tube and abdominal wall defects. A first trimester test conducted between the 10th and 14th weeks of pregnancy combines yet another blood test and an ultrasound test. This screening looks for signs of Down syndrome, trisomy 18 and heart defects.

Chorionic Villus Sampling

Chorionic villus sampling (CVS) is the earliest diagnostic test that can be performed while you are pregnant. CVS is performed between the 10th and 12th weeks of pregnancy, says Mayo Clinic genetic counselor Carrie A. Zabel. It’s more invasive and carries a slightly higher risk of miscarriage than amniocentesis. During this procedure, your doctor will guide a very slender needle through your cervix to obtain a sample of chorionic villi, the tissue attached to the placenta. The results of CVS can rule out chromosomal abnormalities, such as Down syndrome, and genetic disorders, like Tay-Sachs disease and cystic fibrosis, says the Mayo Clinic. However, there is a slight chance that you’ll get a false-positive result from this test. CVS cannot tell you if your developing baby is absent of all birth defects, such as spina bifida.

Amniocentesis

Amniocentesis can be performed during your second trimester, between the 14th and 20th weeks of pregnancy. This test is different from chorionic villus sampling in that rather than going in through your vagina, your doctor inserts a thin needle into your uterus through your belly. A small amount of your amniotic fluid is then collected and tested. When done for genetic purposes, the results from amniocentesis can help you rule out specific disorders, such as Down syndrome; however, Mayo Clinic experts caution that these results won’t assure you that your baby will be born without any birth defects.

Other Purposes

CVS and amniocentesis can serve a dual purpose–to establish paternity–if this is something of which you are unsure. However, as noted by the American Pregnancy Association, you’ll need your doctor’s permission if you intend to use these tests for the express purpose of paternity testing, due to the slight risk of miscarriage.

Genetic Counseling

In most cases, genetic testing on you or your child’s father cannot tell you if your child will inherit a birth defect, says the ACOG. Therefore, diagnostic testing during pregnancy may be the only way to get conclusive information about your developing child. However, as Mayo Clinic experts point out, genetic testing is not something you must have done. It is a personal decision. If you feel that genetic testing may be appropriate for you, consulting with a genetic counselor may guide you through the decision-making process.