Abstract: Objective To investigate the effect of di-(2-ethylhexyl) phthalate (DEHP) exposure on the growth and development of placenta, uterine natural killer (uNK) cell number and angiogenesis at the maternal-fetal interface in pregnant mice. Methods From day 1 of pregnancy, pregnant mice were exposed daily to DEHP by oral gavage at 125, 250, or 500 mg/kg for 13 consecutive days. The uterine and placental tissues were then harvested for HE staining and immunohistochemistry to examine the effect of DEHP exposure on the growth and development of the placenta and angiogenesis and uNK cell number at the maternal-fetal interface. Results Compared with the control group, the mice exposed to 500 mg/kg DEHP, but not those exposed to 125 and 250 mg/kg, showed significantly reduced number of embryo implantation (P<0.05). DEHP exposure significantly increased the rate of abortion. DEHP exposure at 125, 250, and 500 mg/kg significantly and dose-dependently lowered the placental weight compared with that in the control group (0.0637±0.0133, 0.0587±0.0176, 0.0524±0.0183 g vs 0.0786± 0.0143 g, respectively; P<0.01), and significantly reduced the total area of the placenta and area of spongiotrophoblasts. DEHP exposure resulted in a significant reduction in the number of fetal vascular branches, and collapse and atresia of blood vessels. The mice exposed to DEHP at 125, 250, and 500 mg/kg had significantly lowered numbers of uNK cells (83.2±10.3, 60.7±12.4, and 50.4±14.5/HP, respectively) as compared with the control group (105.1±14.2/HP) at the maternal-fetal interface (P<0.01). Conclusion DEHP exposure significantly affects the growth and development of the placenta in mice possibly by suppressing angiogenesis and reducing uNK cell number at the maternal-fetal interface during pregnancy.