Identification of a bactericidal factor (B-lysin) in amnionic fluid at 14 and 40 weeks' gestation.

Amnionic fluid (AF) specimens from 40 normal obstetric patients at 14 to 16 weeks' gestation and at 37 to 40 weeks' gestation were found to contain both lysozyme and a bactericidal substance identified as B-lysin. The concentrations of both lysozyme and B-lysin were significantly higher in the AF at 40 weeks' than at 14 weeks' gestation. B-lysin concentration in AF were also found to be significantly higher than in either cord or maternal blood.