This is a plasma protein normally produced by the fetus' liver. AFP eventually finds its way into the mother's blood and the amniotic fluid. When too much or too little AFP enters the mother's blood stream it can be a sign of fetal problems, such as birth defects. High AFP levels in the mother's blood indicates an increased risk of fetal spina bifida, anencephaly, or other malformations. Low AFP levels are associated with an increased risk of Down Syndrome (trisomy 21) and other chromosomal problems. AFP testing is offered to almost all pregnant women in the U.S., ideally between 16 and 18 weeks gestation. Measuring the AFP level is not sufficiently accurate in screening for Downs- AFP testing should be combined with other tests. Don't assume your child has Down syndrome or spina bifida just because you had an abnormal AFP test result. The AFP test assesses risk, it does not diagnose disease. Unfortunately, many abnormal test results are falsely abnormal and do not reflect a problem with the fetus or mother. If the AFP test is abnormal, additional testing should be performed.