High maternal serum alkaline phosphatase as an index of meconial amniotic fluid.

High level of maternal serum alkaline phosphatase (AP) (above 4 Bessey-Lowry units) was found to be indicative of meconium-stained amniotic fluid (AF). Simultaneous maternal serum AP and AF AP were measured in two groups: group A, the study group (78 cases), parturients with meconium-stained AF, and group B (29 cases), the control group, parturients with clear AF. A positive significant correlation was found between the level of AP in the AF and the level of AP in the parturient's serum, when meconium was present. It is our feeling that the high level of AP in the maternal serum is due to transfer of heat-labile AP from the meconium-stained AF, meconium being rich in AP. The mechanism has as yet to be elucidated.