Maternal serum progesterone-induced blocking factor at 11-13 weeks' gestation in spontaneous early preterm delivery.

OBJECTIVE Progesterone-induced blocking factor (PIBF) may be the mediator of the pregnancy maintenance effects of progesterone. The aim of this study is to investigate the potential value of measuring the maternal serum concentration of PIBF at 11-13 weeks' gestation in the prediction of spontaneous early preterm delivery. METHOD The maternal serum concentration of PIBF at 11-13 weeks was measured by enzyme-linked immunosorbent assay in 25 singleton pregnancies which subsequently delivered spontaneously before 34 weeks, and 75 controls who delivered at or after 37 weeks. The values in the 2 groups were compared by the Mann-Whitney U test. RESULTS The median maternal serum concentration of PIBF in women who subsequently delivered before 34 weeks (157.5, interquartile range 99.5-208.8 ng/ml) was not significantly different from the control group delivering at term (167.5, interquartile range 105.0-212.0 ng/ml; p = 0.519). CONCLUSIONS In women who have a spontaneous early preterm delivery, the maternal serum levels of PIBF are not altered at 11-13 weeks of gestation.