Breast cancer is diagnosed in ~0.3% of pregnant women. Studies that have addressed gestational and neonatal outcomes of chemotherapy during pregnancy have demonstrated increased gestational complications including preeclampsia and intrauterine growth retardation. We hypothesized that anthracycline-induced gestational complications could be derived from direct toxicity on the placenta vasculature. Pregnant ICR mice (day E12.5) were treated with doxorubicin (DXR; 8 mg/kg) or saline, while their umbilical cord blood flow was imaged by pulse-wave (PW) Doppler. Mice were euthanized on day E18.5, and their embryos and placentae were collected for further analysis. Unlike control mice, the DXR-treated mice presented an acute change in the umbilical cord’s blood flow parameters (velocity time integral and heart rate interval), reduced embryos’ weight, reduced placenta efficiency, and modulation in vascular-related pathways of treated placenta proteomics. Apoptosis and proliferation were also enhanced, as demonstrated by TUNEL and proliferating cell nuclear antigen (PCNA) analysis. We further examined the placentae of patients treated with epirubicin (EPI), who had been diagnosed with breast cancer during pregnancy (weeks 27–35). The immunohistochemistry of the EPI-treated human placentae showed enhanced proliferation and apoptosis as compared with matched chemo-naïve placentae, as well as reduced neovascularization (CD34). Our findings suggest that anthracycline-induced vascular insult promotes placental toxicity, and could point to potential agents designated to offset the damage and to reduce gestational complications in pregnant cancer patients.