Some women undergo screening tests during pregnancy. Her doctor will evaluate each woman and decide on an individual basis if she needs a particular test. These tests alert doctors of potential problems with the fetus: Alpha-Fetoprotein (AFP) or Maternal Serum Screening
This test analyzes the mother’s blood. The AFP test looks for abnormalities in the fetus’s brain or spinal cord; it can also check for chromosomal disorders such as Down syndrome. This test poses no danger to the mother or baby, so most women will undergo AFP screening between 15 and 18 weeks. A possible drawback to the AFP test is the number of false-positive results it produces; abnormal results will require further testing.
Ultrasound
This screening test uses sound waves to construct a picture of the fetus without the danger of X-ray. Ultrasound can determine a woman’s due date if performed early enough in the pregnancy. It can tell a doctor if a woman is carrying multiple fetuses, determine the condition of the placenta, and check for a breech position prior to delivery. It can also identify the cause of problems such as vaginal bleeding and others. This test can be performed from the fifth week of pregnancy until delivery. Generally, it is performed after the 16th week.
Chorionic Villus Sampling (CVS)
In CVS testing, the doctor takes a sample of the chorionic villi from the placenta via a needle passed through the abdomen or via a tube passed through the vagina and cervix. This test can detect fetal defects as early as the ninth week of pregnancy. This test is not recommended for all women. Women who already have a child with birth defects, who have a family history of birth defects, who are at least age 35 on their due date, and women at risk for certain genetic diseases (or women with an at-risk partner) are candidates for CVS.
Amniocentesis
During amniocentesis, the doctor sticks a needle into the woman’s amniotic sac via the abdomen to extract some of the fluid surrounding the fetus. Analysis of this fluid can detect a number of problems, such as Down syndrome, Tay-Sachs disease, and neural tube defects, among others. This test is given to women with the same risk factors as the women who undergo CVS testing. A small risk of miscarriage (0.5 percent) is associated with amniocentesis.
