WHY IS AMNIOCENTESIS OFTEN RECOMMENDED WHEN AFP TEST RESULTS ARE ABNORMAL?
Amniocentesis is the procedure used to withdraw a small amount of amniotic fluid (the water in the sac surrounding the fetus). Amniotic fluid contains cells shed from the fetus and includes copies of the genetic material the fetus possesses. Tests done on amniotic fluid yield more accurate results than tests on maternal blood. If the woman is determined to be at risk for having a baby with a neural tube defect, then, along with the level 2 (targeted) ultrasound exam, very often amniocentesis is recommended also. Approximately 98% of all open neural tube defects can be detected by testing amniotic fluid. If the fetus is at risk for having Down Syndrome, then amniocentesis will detect this with greater than 99% accuracy when this chromosome abnormality is present.
