Screening for Birth Defects


Screening Tests for Birth Defects

Most pregnancies end with the birth of a healthy baby. However, every pregnant woman has a small chance of having a baby with a birth defect. Out of 100 newborns, only two or three have major birth defects. Birth defects are problems newborns may develop during pregnancy that potentially affect their physical appearances, bodily functions or both.

Birth Defects

Studies reveal that birth defects occur within the first three months of pregnancy, which is why doctors encourage expecting mothers to consider early screening tests to help assess the risk of a birth defect. Prenatal screening tests, ordered by an OB/GYN physician, can find defects including chromosome abnormality and other medical conditions before a baby’s birth. Approximately 4,000 different defects exist, ranging from mild impact to major long-term complications.

Some of the most common birth defects found through screening tests include:

Defects caused by congenital infections occur when a mother gets an infection before or during the pregnancy. These types of birth defects include Rubella and Cytomegalovirus, which are the most common congenital infections.
Genetic disorders — which occur when a faulty gene is present or if a gene is missing. The most common genetic disorders include Down Syndrome and Trisomy 18.
Hereditary diseases — which are passed to children from previous generations. Just as a baby gets certain traits like eye color from the parents, certain diseases or disorders can be passed on to the baby. The most common types of this disease include Sickle Cell Anemia and Cystic Fibrosis.
Structural problems  — refers to problems manifesting when a specific body part is missing or formed incorrectly. The most common type of structural defect includes those involving heart structure. These affect 1 in 150 babies in the United States.

According to the Centers for Disease Control and Prevention, birth defects are one of the leading causes of infant deaths, accounting for more than 20 percent of all infant deaths. Babies born with birth defects have a greater chance of illness and long-term disability than babies without birth defects.

Screening Tests

OB/GYN clinics and other women’s health facilities offer optional prenatal screening tests for all pregnant women, of any age. Women may choose between undergoing a single test or a combination of tests. Although screening tests do not detect all health problems or all types of mental retardation, they can reveal if you have a higher or lower chance of having a baby with certain birth defects. A variety of tests are offered based on the stage or trimester of your pregnancy.

First trimester screening tests occur between 11 and 14 weeks of the pregnancy and include blood tests and an ultrasound exam to examine the risk of chromosomal problems. If abnormalities result from the initial screening tests, a detailed follow-up ultrasound can reveal an extensive view of the baby’s organs and can generally be done after 18 weeks of pregnancy. Second trimester screening involves testing substances in a pregnant woman’s blood and usually performed during the15-20 weeks of the pregnancy. It can help find pregnancies with neural defects of the brain or spine of the baby and abdominal defects of the baby’s stomach. If the results of these screening tests raise concerns about your pregnancy, diagnostic tests can be performed to provide more information. The decision to have testing or not and which tests to choose is up to you.

Your doctor will explain the risks and benefits of the screening tests, provide you with other resources for support and help you make the best choice in your decision making process.

Decision Making

Your health care provider suggests prenatal tests to ensure that the baby is growing and developing healthy. Ask your OB/GYN doctor for educational resources that might be helpful to you. Obstetricians encourage you to take responsibility for your prenatal care and make the right decision for you and your child. Of course your periodic visits to your doctor help monitor the overall health of you and your baby.