Parents to be can choose to have a number of prenatal screening tests performed. Some tests are designed to diagnose a birth defect, while others only measure the level of risk that exists for certain medical conditions. If the screening test results reveal a high level of risk for a medical problem, then the woman and her partner need to make a decision about whether they want to have further testing done.
When a woman goes to see her doctor because she suspects she is pregnant or has seen a positive result on a home pregnancy test, the physician will order some routine prenatal screening tests. The woman will be asked to provide a urine sample at each visit. This sample will be used to screen for elevated protein levels, which indicate pre-eclampsia, and sugar levels that would cause concern about gestational diabetes.
Pre-eclampsia is pregnancy-related hypertension and it can be very serious, even life-threatening, for the mother and baby if not controlled. Other signs of pre-eclampsia are sudden, severe headaches and swelling in the legs and feet. Gestational diabetes occurs when the mother's body is not able to produce enough insulin to meet her own and the baby's needs. Fatigue, excessive thirst and blurred vision are all symptoms of this condition. A pregnant woman who experiences any of these symptoms should see her health care provider right away.
In the United States, a pregnant woman may be offered a first trimester screen. The two-part test involves a blood sample being taken from the pregnant woman, along with an ultrasound examination of the developing fetus. This test evaluates the woman's risk for certain birth defects, such as Trisomy 18 and Down Syndrome. It can also be used to diagnose cardiac abnormalities, but is not used for determining if the child has neural tube defects, such as spina bifida.
Other prenatal screening tests are used for diagnostic purposes. An amniocentesis is an invasive test where a small amount of amniotic fluid is removed from the uterus for analysis. It is a highly effective way of diagnosing birth defects like Down Syndrome, cystic fibrosis, muscular dystrophy and sickle cell disease. This test may also be performed to determine whether an unborn baby's lungs are sufficiently developed so that the child can breathe on his or her own if a premature delivery is being considered. As with all prenatal screening tests, the potential benefits must be carefully weighed against the risks involved before making a decision.