Subacute exposure to DEHP leads to impaired decidual reaction and exacerbates the risk of early miscarriage in mice.

Objectives: To investigate the effect of subacute exposure of Di (2-ethylhexyl) phthalate (DEHP) on endometrial decidualization and early pregnancy miscarriage in mice.

Methods: CD1 mice were orally administrated with 300 (low-dose group), 1000 (medium-dose group), or 3000 mg·kg^－1·d^－1 DEHP (1/10 LD₅₀, high-dose group) for 28 days, respectively. An early natural pregnancy model and an artificially induced decidualization model were established. The uterine tissues were collected on D7 of natural pregnancy and D8 of artificially induced decidualization, respectively. The effects of a subacute exposure to DEHP on the decidualization of mice were detected by HE staining, Masson staining, TUNEL assay, and Western blotting. A model of spontaneous abortion was constructed in mice after subacute exposure to 300 mg·kg^－1·d^－1 DEHP, and the effect of impaired decidualization on pregnancy was investigated by observing the pregnancy outcome on the 10th day of gestation.

Results: Compared with the control group, the conception rate was significantly decreased in the high-dose DEHP subacute exposure group (P<0.05). HE staining showed that, compared with the control group, the decidual stromal cells in the low- and medium-dose exposure groups were disorganized, the nuclei of the cells were irregular, the cytoplasmic staining was uneven, and the number of polymorphonuclear cells was significantly reduced. Masson staining showed that compared with the control group, the collagen fibers in the decidua region of the DEHP low-dose group and the medium-dose group were more distributed, more abundant and more disorderly. TUNEL assay showed increased apoptosis in the decidua area compared to the control group. Western blotting showed that the expression of BMP2, a marker molecule for endometrial decidualization, was significantly reduced (P<0.05 or P<0.01). The abortion rate and embryo resorption rate were increased, and the number of embryos, uterine wet weight, uterine area and placenta wet weight were decreased in DEHP low-dose group compared to the control group stimulated by mifepristone, an abortifacient drug (P<0.05 or P<0.01).

Conclusions: Subacute exposure to DEHP leads to impaired endometrial decidualization during early pregnancy and exacerbates the risk of adverse pregnancy outcomes in mice.