Embryolethality of butyl benzyl phthalate during early pregnancy in rats.

In our previous studies, butyl benzyl phthalate (BBP) was found to be embryolethal and teratogenic in rats. In order to extend these findings, the effects of BBP during early pregnancy on maternal parameters were examined. Pregnant rats were given dietary BBP at 2.0% on day 0 through the day of sacrifice, day 7, 9, or 11 of pregnancy. The number of corpora lutea and implantations and the incidence of preimplantation embryonic loss were comparable across all groups. The postimplantation embryonic loss on day 11 in the 2.0% BBP group was markedly higher than that in the control and pair-fed groups. Regardless of the day of sacrifice, the uterine and ovarian weights and plasma progesterone levels, except for the ovarian weight on day 7, in the 2.0% BBP groups were significantly lower than those in the control and pair-fed groups. These findings suggest that the postimplantation embryonic loss due to BBP during early pregnancy is mediated via the reduction in plasma progesterone levels, an impairment of luteal function.