Sahin ME, Madendag IC, Sahin E, et al. - Researchers investigated whether women with unexplained infertility differed from fertile women in terms of the progesterone-induced blocking factor (PIBF) level. Using an enzyme-linked immunosorbent assay, measurement of serum PIBF levels was done in 46 healthy participants (18 to 35 years old) in the study. Of the participants, 22 had unexplained infertility. Findings revealed significantly lower serum PIBF levels in unexplained-infertility group vs the fertile control group.