GENETIC TESTING

Genetic testing helps to identify health problems in the developing fetus.  Some tests are screening tests, meaning they can reveal the possibility of a problem.  Others are diagnostic tests, which determines with certainty whether a problem exists.

Screening tests:

  1. First trimester screening (done at 11-14 weeks):  a maternal blood test for 2 pregnancy hormones plus an ultrasound measurement of the thickness behind the fetal neck
  2. Quad screening (done at 15-20 weeks):  a maternal blood test for 4 pregnancy hormones
  3. Cell free DNA testing (done after 9 weeks):  identifies fetal DNA in maternal blood to see if there are extra or missing chromosomes

Diagnostic tests:

  1. Chorionic villus sampling (done at 10-14 weeks):  a piece of placental tissue is removed abdominally or vaginally and the fetal chromosomes are analyzed
  2. Amniocentesis (done at 15-20 weeks):  amniotic fluid is removed abdominally and the fetal chromosomes are analyzed

 

All women can have the first trimester and quad screening test.  The other tests – cell free DNA, CVS, and amniocentesis – are reserved for women over age 35 or those with a history of genetic abnormalities.  You should talk to your doctor early in the pregnancy about which tests may be right for you.