• Natural killer cells;
  • progesterone receptors;
  • T-lymphocytes

PROBLEM: An immunomodulatory protein known as the progesterone induced blocking factor (PIBF) has been found to positively correlate with early pregnancy beta human chorionic gonadotropin (B-hCG) levels. The study presented herein evaluated PIBF levels from conception to the end of the first trimester to determine if lower levels will correlate with first trimester spontaneous abortions (SAB).

METHOD: Progesterone induced blocking factor expression by lymphocytes measured using an immunocytochemistry method was compared in pregnant women with ongoing vs. failed pregnancies.

RESULTS: There were no differences in the proportion of women having lymphocytes expressing PIBF or in the median numbers when comparing ongoing vs. failed pregnancies. There was no B-hCG interval where failed pregnancies were found to have lower frequency of PIBF expressing lymphocytes.

CONCLUSION: Inadequate PIBF expression independent of low P levels does not appear to be an etiologic factor for first trimester SABs; thus measuring this protein in pregnant women lacks practical usefulness.