Birth defects can be diagnosed during pregnancy or after birth, depending on the specific type of birth defect.
A screening test is a procedure that is conducted to see if a woman or baby might have any problems during fetal development.
First trimester screening is a combination of tests completed between weeks 11 and 13 of pregnancy. It is used to look for certain birth defects related to the baby’s heart or chromosomal disorders. This screen includes:
Maternal blood test, a simple blood test that measures the levels of two proteins, human chorionic gonadotropin (hCG) and pregnancy associated plasma protein A (PAPP-A). If the protein levels are abnormally high or low, there could be a chromosomal disorder in the baby.
Ultrasound, an imaging method that creates pictures of the baby during the first trimester to look for extra fluid behind the baby’s neck. If there is increased fluid found on the ultrasound, there could be a chromosomal disorder or heart defect in the baby.
Second trimester screening tests are completed between weeks 15 and 20 of pregnancy and include a maternal serum screen and a comprehensive ultrasound evaluation of the baby looking for the presence of structural anomalies.
Maternal serum screen, a simple blood test used to identify if a woman is at increased risk for having a baby with certain birth defects, such as neural tube defects or chromosomal disorders. It is also known as a triple screen or quad screen depending on the number of proteins measured in the mother’s blood.
Anomaly ultrasound, usually completed around 1820 weeks of pregnancy. The ultrasound is used to check the size of the baby and looks for birth defects or other problems with the baby.
If the result of a screening test is abnormal, doctors usually offer further diagnostic tests to determine if birth defects or other possible problems with the baby are present. These diagnostic tests are also offered to women with higher risk pregnancies, which may include women who are 35 years of age or older; women who have had a previous pregnancy affected by a birth defect; women who have chronic diseases such as lupus, high blood pressure, diabetes, or epilepsy; or women who use certain medications.
High resolution ultrasound, also known as a level II ultrasound, is used to look in more detail for possible birth defects or other problems with the baby that were suggested in the previous screening tests. It is usually completed between weeks 18 and 22 of pregnancy.
Chorionic Villus Sampling (CVS) is a test where the doctor collects a tiny piece of the placenta, called chorionic villus, which is then tested to check for chromosomal or genetic disorders in the baby. Generally, a CVS test is offered to women who received an abnormal result on a first trimester screening test or to women who could be at higher risk. It is completed between 10 and 12 weeks of pregnancy, earlier than an amniocentesis.
Amniocentesis is a test usually completed between 15 and 18 weeks of pregnancy, where the doctor collects a small amount of amniotic fluid from the area surrounding the baby. The fluid is then tested to measure the baby’s protein levels, which might indicate certain birth defects.
After the Baby is Born
Certain birth defects might not be diagnosed until after the baby is born. Sometimes, the birth defect is immediately seen at birth. For other birth defects including some heart defects, the birth defect might not be diagnosed until later in life. When there is a health problem with a child, the primary care provider might look for birth defects by taking a medical and family history, doing a physical exam, and sometimes recommending further tests. If a diagnosis cannot be made after the exam, the primary care provider might refer the child to a specialist in birth defects and genetics. A clinical geneticist is a doctor with special training to evaluate patients who may have genetic conditions or birth defects. Even if a child sees a specialist, an exact diagnosis might not be reached.