Alpha1-antitrypsin concentration in amniotic fluid.

Concentrations of alpha1-antitrypsin were measured in 80 specimens of amniotic fluid collected at various stages of pregnancy. Levels remained relatively unchanged throughout gestation, with a median concentration of 10.0 mg/100 ml at 12-24 weeks, 18.7 mg/100 ml at 34-37 weeks, and 16.2 mg/100 ml, after the 37th week. In three instances where the infant developed RDS, the median concentration was 12.4 mg/100 ml.