Amniotic fluid AFP (AFAFP) levels peak at about 13 weeks of gestation after which they decline rapidly until 22 weeks of gestation and then show a gradual decline until term. In Open Neural Tube defects AFP leaks directly into the amniotic fluid causing unexpectedly high levels. Certain fetal abnormalities like Congenital renal disease and Esophageal atresia also show high AFAFP levels.