Screening Tests During Pregnancy


There are a variety of prenatal screening tests that are available for women who are pregnant. The number, types and frequency of testing are determined on a cases by case basis, taking into consideration risk factors, maternal age, medical history, etc. The first trimester prenatal screening tests involve a combination of a fetal ultrasound and maternal blood testing to help determine the risk of the fetus having certain birth defects. The first trimester prenatal screening includes the following:

  1. Nuchal Translucency Ultrasound – an ultrasound used to closely examine the area at the back of the fetal neck. It looks for increased fluid which can be an indication of certain types of birth defects.
  2. Maternal Serum (blood) tests to measure the amount of pregnancy associated plasma protein (PAPP-A) and human chorionic gonadotropin (hCG). Abnormal levels of either or both of these two substances can be an indicator of chromosomal abnormalities.

If the results of this first trimester screening are abnormal, further testing such as amniocentesis or chorionic villus sampling may be recommended in order to make an accurate diagnosis.

Second Trimester Screening may include several maternal blood tests, often referred to as “multiple markers.” This involves taking a maternal blood sample sometime between weeks fifteen and twenty of pregnancy. If any of these markers are abnormal, further testing may be recommended. Multiple marker screening is not diagnostic but is used as a way to determine who should receive additional testing.

A glucose tolerance test is another prenatal screening that can be used. This maternal blood test is usually performed between weeks twenty-four and twenty-eight of pregnancy and measures the level of sugar (glucose) in the mother’s blood. Abnormal glucose levels can be an indication of gestational diabetes.

A group B strep culture is another screening test that is used to detect the presence of Group B Streptococcus (GBS), a bacteria that can exist in the lower genital tract of women. This test is usually performed between weeks thirty-five and thirty-seven of pregnancy. If left untreated, this bacteria can cause serious complications to both the mother and the child.

For more information about the prenatal screening tests that are available, talk to your Obstetrician today. Your doctor will be able to determine which tests are needed and when they should be conducted.