Women who are tested in their second trimester may be faced with the dilemma of deciding whether to carry their babies to term or to terminate the pregnancy. It is important to recognize that not all suspicious results indicate a problem with the fetus, just as normal results do not definitively rule out any potential problems.
False-positive results are a concern with MSAFP screening. False-positives readings from elevated levels of AFP can be due to twins, threatened abortion, inaccurate dates, low-birth-weight infants, a placental defect (large or malpositioned) or a sample contaminated with blood. Abnormally low readings may result from incorrect dating, a female fetus or diabetes.
The triple screen, which includes three markers -- MSAFP, human Chorionic Gonadotropin (hCG) and estriol -- is a more accurate test than the MSAFP. It detects chromosomal anomalies, including Down Syndrome. Ideally, this test should be drawn between 16 to 18 weeks from the last menstrual period. This test improves the detection of chromosomal anomalies by 60 percent among women aged 35 and over. If the triple screen is available, it should be requested in preference to the AFP alone. Because of its superior accuracy, it can help pregnant women avoid unnecessary amniocentesis.