Secretory component of immunoglobulin A in maternal serum and the prediction of preterm delivery

OBJECTIVE: Our purpose was to determine whether the secretory component of immunoglobulin A in maternal serum predicts delivery before 34 weeksʹ gestation. STUDY DESIGN: Primigravid women of an urban population in New Zealand were recruited at booking into a prospective longitudinal nested case control study (n = 1651; after exclusions and withdrawals, n = 1511). Serum was collected at 8 to 12 weeks, 15 to 18 weeks, 21 to 24 weeks, 28 to 30 weeks, and 36 to 38 weeks of gestation and 6 weeks post partum. Concentrations of the secretory component of immunoglobulin A were determined by enzyme-linked immunosorbent assay in all women who were delivered preterm (n = 53) and in controls randomly selected from women delivered at ≥37 weeksʹ gestation (n = 178). RESULTS: Serum concentrations of the secretory component of immunoglobulin A were similar in women delivered at term or preterm throughout pregnancy (n = 21 delivered at <34 weeks and n = 32 at 34 to 36.9 weeks, incidence 3.5%). Receiver-operator characteristic curves showed no discriminating ability of the secretory component of immunoglobulin A. Smokers had 50% higher concentrations than nonsmokers did (p< 0.0001 by analysis of variance). CONCLUSION: The secretory component of immunoglobulin A in maternal serum does not predict preterm delivery in a low-risk population. (Am J Obstet Gynecol 1998;178:535-9.)