How are neural tube defects diagnosed?

Neural tube defects are detected through an AFP (Alpha-fetoprotein test) a blood test administered at 16-18 weeks gestation. The test measures alpha-fetoprotein, a substance produced by the fetus and secreted into the amniotic fluid, eventually entering the mother's blood. The level of AFP in mother's blood peaks at about 30-32 weeks. Abnormally high amounts of AFP may indicate a baby has a neural tube defect.