Biochemical assessment of fetal lung maturity.

The relationship between the enzyme phosphatidate phosphohydrolase (PAPase) and lecithin/sphingomyelin (L/S) ratio in amniotic fluid was evaluated in normal human pregnancies and in several pregnancies complicated by Rh isoimmunization. An increase in PAPase activity in amniotic fluid appears to parallel the increase in L/S ratio after 33 weeks gestation in normal subjects. These data suggest that amniotic fluid PAPase may originate from the fetal lung and play a role in the regulation of the synthesis os lecithin. Its usefulness as an indicator of fetal lung development requires further correlation and confirmation.