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. Prenatal testing can find some of these birth defects before a baby is born. Prenatal tests do not detect all birth defects or all types of mental retardation, nor do they detect most health problems.
Prenatal tests help to find specific kinds of birth defects, including chromosome abnormalities (like Down syndrome), and other conditions, such as spina bifida. These types of birth defects do not usually run in the family, so they can happen in any pregnancy unexpectedly. The risk for chromosome abnormalities gradually increases with age, but a woman of any age can have a baby with a chromosome abnormality.
To find your chance to have a baby with a chromosome abnormality: Maternal age risks
Prenatal tests for birth defects can be separated into screening tests and diagnostic procedures. Both types of prenatal tests are available for pregnant women of any age.
Prenatal screening tests look at many different things about a pregnancy, such as results from blood testing, the mother's age, or ultrasound findings, to estimate the chance for certain birth defects. Screening tests are not able to diagnose birth defects.
Prenatal diagnostic procedures are specialized tests that can accurately diagnose certain birth defects during pregnancy.Chromosome abnormalities and neural tube defects are the most common conditions we look for with routine diagnostic procedures. Testing for other conditions can sometimes be done in pregnancies at special risk.
These prenatal tests are optional, so the decision to have testing or not, and which test to choose, is up to you. To find out more, here's a short program about prenatal testing:
If you are considering a pregnancy, but are not yet pregnant, the California initiative called "Every Woman California" can give you information about steps to take to improve your chances for a healthy pregnancy.