Effects of administration of a non-specific immunostimulant prior to mating on pregnancy establishment and fetal and placental development in mice

Early embryonic mortality occurs in many mammalian species, including mice, humans and several livestock species. Previous work in mice has demonstrated a role for pro-inflammatory cytokines and immune cells in stimulating ovarian function and uterine receptivity during the peri-conception period. The objective was to determine if administration of an immunostimulant could improve pregnancy establishment and fetal survival. At proestrus/estrus, female mice (CB6F1) were randomly assigned to treatment with 0, 20 or 40 μg of mycobacterium cell wall fraction (MCWF; n = 73/treatment). Treatments were administered intraperitoneally prior to overnight exposure with males (BALB/c). A subset of females (n = 21/treatment) were sacrificed at gestational day (gd) 4.5 for assessment of spleen and liver weights. The remaining females were sacrificed at gd 17.5 to determine the number of viable fetuses and resorbing implantation sites, and fetal and placental weights. Treatment with MCWF increased spleen weight at gd 4.5 for both the 20 and 40 μg dose levels. However, there was no effect of MCWF treatment on the number of viable fetuses and resorbing implantation sites, nor fetal and placental weights on gd 17.5. Administration of MCWF during the periovulatory period induced an inflammatory response, but did not impact pregnancy establishment, fetal survival or placental development. Results are somewhat inconsistent with those observed in other species and may be impacted by the timing and route of administration.