Serum concentrations of secretory IgA in pregnancies delivering at term or preterm.

Secretory component (SC) is a phospholipase A2 inhibitor possibly associated with pregnancy maintenance and in serum is bound either to IgA (sIgA) or IgM (sIgM). To determine if serum secretory component levels a) increase during pregnancy, b) fall as term approaches, c) are low in women who will deliver prematurely, serum sIgA was measured at "booking in" and related to weeks of gestation and length of gestation at subsequent noninduced delivery. Levels of sIgA increased during pregnancy; sIgA increased from a non-pregnant value of 1.6 nM +/- 0.2 (mean +/- SEM) to 2.8 nM +/- 0.3 at the end of the second trimester, then fell significantly between 31-34 weeks. Delivery before 37 weeks was associated with significantly reduced serum sIgA levels, particularly in women who delivered before 32 weeks and in whom sIgA concentrations were similar to those of nonpregnant women.