Alpha1-antitrypsin in amniotic fluid and cord blood of preterm infants with the respiratory distress syndrome.

Total protein, alpha1-antitrypsin, and alpha2-macroglobulin were measured on amniotic fluid in 125 pregnancies between 11 and 42 weeks' gestation, and on the cord blood of 66 newborn infants. Amniotic fluid surface active material was assessed by the foam stability test. Amniotic fluid alpha1-antitrypsin is linearly and directly related to amniotic fluid total protein (r = 0.703, p less than 0.001). The cord alpha1-antitrypsin is also linearly related to cord total protein. Intrapartum complications are associated with a significant lowering of the cord alpha1-antitrypsin. Infants with a negative foam stability test had RDS regardless of the amniotic fluid alpha1-antitrypsin. The cord blood alpha1-antitrypsin value did not appear to be related to amniotic fluid surface active material. There were 23 infants with cord alpha1-antitrypsin of less than 0.2 gm/dl and with an intermediate or positive foam stability test; 19 of them had respiratory difficulties of varying severity. It is conceivable that infants, in spite of apparent adequate prenatal lung surfactant, develop respiratory disturbances on the basis of pulmonary fluid and protein transudation and/or reduction or inhibition of pulmonary surfactant incident to intrapartum complications.