Progesterone-Induced Blocking Factor (PIBF) as a possible Early Diagnostic Marker of Pregnancy

Nina Davidova, Lali Pkhaladze, Archil Khomasuridze


Background: Pregnancy loss is one of the main issues of contemporary Reproductology with the prevalence 12%, amounting to 55% in case of 3 consecutive miscarriages. Presumably, 50% of miscarriages occur before the delay of menstruation.

Pregnancy seems to be a purely immunological phenomenon. Embrioprotective factors are being activated from the first day of pregnancy. One of them is progesterone-induced blocking factor (PIBF), which is produced in CD56+ cells and mononucleocytes. It impairs pro-inflammatory cytokines’ production, suppresses constriction of the myometrium, shifts the production of Th1 towards Th2, and blocks the natural killer (NK) cells degranulation.

Aim: The purpose of this article is to summarize the extant knowledge on the effects of PIBF and to estimate its significance as a possible early diagnostic marker of pregnancy.

Method: The data were collected from NCBI, PubMed, ScienceDirect databases by using the keywords: progesterone-induced blocking factor, immunology of pregnancy, progesterone, pregnancy. The years for the search were between 1985 and 2021. 

Conclusions: The level of PIBF increases soon after conception, contributes to the modulation of the mother’s immunity and pregnancy maintenance. Its significance, as an early diagnostic marker of pregnancy, is not defined, though it may be informative at the first two weeks of gestation. Therefore, the studies must be continued in this connection.

Keywords: Early pregnancy loss; Progesterone-induced blocking factor (PIBF); Miscarriage; Immunity of pregnancy; Progesterone (P4).

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ISSN: 2346-8491 (online)