In vitro defects of phagocyte chemotaxis during pregnancy.

Pregnant women have an increased risk for some infections, particularly during the last trimester. Phagocytic emigration from the circulation into tissues is an important aspect of the initial immune response. Therefore, circulating phagocytes of 42 pregnant and 15 postpartum patients were studied in vitro for random and chemotactic (or directional) migration through membrane filters (Millipore Corp., Bedford, Mass.). Random migration of phagocytes from all 42 pregnant patients studied in each trimester was within normal limits. Chemotactic migration of 25 patients who were between 6 and 33 weeks of pregnancy was also similar to values obtained with control leukocytes (20 nonpregnant, normal females. However, phagocytes of 17 other women studied between week 34 of pregnancy and term showed marked depressions in chemotaxis (P less than 0.001 from control values). During labor and within 3 days of delivery, chemotactic migration increased to supranormal levels in 14 of 15 women studied. Sera from six pregnant patients with proven chemotactic defects did not reduce migration when incubated with normal phagocytes. These chemotactic defects appear to be intrinsic and may be important in predisposing to infections during late pregnancy.