Maternal serum progesterone-induced blocking factor (PIBF) in the prediction of preterm birth

•We analyzed the maternal serum concentration of progesterone-induced blocking factor.•The study was conducted on a sample of 78 women.•The onset of labor could be predicted on the basis of PIBF serum concentrations.•Pregnancy termination can be predicted by lower PIBF values.

The objective of this study was to analyze the maternal serum concentration of progesterone-induced blocking factor (PIBF) with regard to the prediction and the interval between sampling and the onset of preterm birth. A prospective study was conducted on a sample of 37 women with threatened pre-term birth and 41 healthy pregnant women between the 24th and 28th gestational weeks. Out of 37 patients with threatened preterm birth 11 delivered pre-term and three groups of patients were formed: the preterm delivery group, patients with threatened preterm delivery, and healthy pregnant women. In samples that were taken within 5 days before labor started (6/11, 54.5%), PIBF concentrations were significantly lower than in those obtained more than 5 days before labor (5/11, 45.5%; the mean interval between sampling and the onset of labor was 4.1 ± 1.8 days). Multiple regression analysis of the individual contributions of each observed parameter for preterm delivery demonstrated the significant contribution of a lack of PIBF to preterm birth (p = 0.002). Receiver operating characteristics (ROC) analysis was performed to evaluate the diagnostic accuracy of PIBF for the prediction of preterm birth of women with symptoms of pre-term delivery. The PIBF demonstrated an excellent diagnostic value in the prediction of preterm birth with an area under the ROC curve (AUC) of 0.956 (95% CI = 0.884-0.989; p < 0.0001). Our data suggest that pregnancy termination can be predicted by lower than normal pregnancy PIBF values within 5 days before labor and can contribute to the diagnosis of preterm birth.