Maternal and cord blood complement activity: relationship to premature rupture of the membranes.

Human complement levels are known to reflect the presence of clinical infection, with low levels indicative of increased utilization in the body's immune response. Premature rupture of the membranes (PRM) is associated with an increased maternal-fetal infectious morbidity, yet histopathologic and bacteriologic parameters often do not reflect this. In this prospective study maternal and cord serum total hemolytic complement activity (CH50) was measured in 102 patients without evidence of infection, with and without PRM, to determine if there exists within the maternal-fetal unit an immunologic response to this event. It was found that maternal serum CH50, regardless of length of gestation, is similar to that of the nonpregnant adult population, except in cases of PRM greater than 12 hours in which it is significantly lower. The CH50 in term newborn infants was significantly lower than that of matched maternal samples and dropped with decreasing gestational age. CH50 in cord serum from babies of mothers with PRM failed to show a significant decrease when compared to those of mothers without PRM.