Produced by fetus, crosses placenta, enters maternal circulation
Results reported as multiples of the median (MoMs)
Depends on accurate gestational dating
Usually part of QUAD screen test
Diagnosis:
Elevated MSAFP ( > 2.5MoMs)
Open neural tube defects
Multiple gestation
Incorrect gestational dating
Placental abnormalities
Gastrochesis / omphalocele
