Perhaps one of the most stressful times for an expectant parent is the time when you have to consider prenatal testing to assess the risk or potential of birth defects.
There are several prenatal screening test options available, including a new non-invasive prenatal screening test available to certain regions in the United States as of March 1, 2013.
Traditional Prenatal Screening
The first prenatal screening tests are done between 11 and 13 weeks and include a maternal blood screen and an ultrasound. The maternal blood screen measures the levels of human chorionic gonadotropin (hCG) and pregnancy-associated plasma protein A (PAPP-A) in the mother’s blood.
An ultrasound measures the amount of fluid behind the baby’s neck. Abnormally high or low levels of these proteins, or an increased or decreased amount of fluid, could indicate a chromosomal abnormality or heart defect in the baby. (1)
Testing in the second trimester through a maternal serum screen and ultrasound is completed between 15 and 20 weeks.
If the result of a screening test is abnormal, a high resolution ultrasound, chorionic villus sampling (CVS), or amniocentesis is usually recommended to confirm whether an anomaly is present and/or which chromosomal disorder or other birth defect may be affecting your baby.
The CVS test is performed between 10 and 12 weeks and involves inserting a needle through the abdomen or through the cervix into the placenta to collect a sample of the chorionic villus.
An amniocentesis is completed between 15 and 18 weeks, and requires a needle to be inserted through the abdomen and uterine wall to withdraw a sample of amniotic fluid.
Both the chorionic villus sampling and the amniocentesis carry a small risk of miscarriage -- 1 in 400 for CVS, and between 1 in 400 and 2- 4 out of 400 for amnio, depending on the study. (2, 3)
Non-invasive Prenatal Screening
Ultrasounds are considered “non-invasive” as there is no direct outside interaction with the baby or anything inside the body. CVS and amniocentesis procedures are considered invasive.