A prospective study of serum complement (C3 and C4) levels in normal human pregnancy: effect of the development of pregnancy-associated hypertension.

Serum levels of complement components (C3 and C4) were measured serially in 173 initially normotensive pregnant women and the results compared with those obtained in 32 nonpregnant women of similar ages. There was significant elevation of serum levels of both C3 and C4 during gestation. Pregnancy-associated hypertension developed in the third trimester in 26 pregnant women but they had the-same degree of elevation of serum C3 and C4 levels as did the 147 pregnant women who remained normotensive throughout their pregnancy. Measurements of serum C3 and C4 levels and therefore of no value in predicting the development of pregnancy-associated hypertension.