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During your pregnancy, your caregiver will suggest prenatal testing to make sure both you and your baby are healthy. Many of the tests are recommended in all pregnancies. Others are recommended if your age or family history puts you at an increased risk of having a baby with a genetic problem.

There are two types of tests: screening tests and diagnostic tests.

Screening Tests

Screening is safe for you and your baby. Though they can't make an actual diagnosis, they can tell you if your baby is more likely to have certain conditions. Here are the most common tests:

• First trimester screen is done between week 11 and 14. First, you'll have a blood test to check for two normal first-trimester proteins. Second, you'll have an ultrasound to measure an area on the back of your baby's neck. The combined results may tell you if your baby has an increased risk of Down syndrome and also may help detect other problems.
• The quad marker screen is a blood test offered to women between weeks 15 and 20 who did not do the first trimester screen. Results will tell you if your baby has an increased risk of certain developmental or chromosomal disorders, such as spina bifida or Down syndrome.
• An ultrasound uses sound waves to take a picture of your baby and what's around him or her. It is usually done at about 18 to 20 weeks, but can vary depending on the needs of each woman.

Diagnostic Tests

If the results of any of the above screening tests indicate a possible problem, your doctor will suggest a diagnostic test. These are more invasive than the screening tests and have some risk.

• During amniocentesis, a needle is inserted into the abdomen and through the uterus to extract a sample of amniotic fluid, which is then tested for genetic problems, such as Down syndrome and spina bifida. This procedure is done after the 15th week of pregnancy. There is a slight risk of miscarriage when done before the 24th week.
• In chorionic villus sampling (CVS), a sample of the placenta is tested for genetic abnormalities between the 9th and 14th week of pregnancy. It can identify chromosomal abnormalities and some specific genetic problems earlier than amniocentesis. To get the sample, a needle is inserted either through the abdomen or the cervix. There is also a risk of miscarriage, higher than the risk with amniocentesis.
• In percutaneous umbilical blood sampling a sample of your baby's blood is tested for genetic problems or infections after the 18th week of pregnancy. The test can identify sickle cell anemia, hemophilia, anemia, Rh disease, and other conditions. The sample is taken from a vein in the umbilical cord through a needle inserted into the mother's abdomen. Risk of miscarriage is two in 100.