Aromatase inhibitors (Als) area class of drugs that act by blocking the production of estrogens from androgens. The current review concentrates on the prenatal developmental toxicity of Als in experimental models. Available data indicate that Als may affect pregnancy at human therapeutic or lower doses. The window of vulnerability to AIs is not limited to organogenesis, but also includes the preimplantation stage and fetal periods. Decreased embryo/fetal survival was the prominent treatment-related effect. Morphological anomalies noted in fetuses exposed to Als included skeletal anomalies, abnormal head morphology, increased ano-genital distance in female fetuses, and minor urinary tract system anomalies. Placental enlargement was consistently reported in rats and non-human primates after maternal treatment with several AIs. In conclusion, data from basic scientific research suggest that low intensity exposure to Als applied during a wide gestational window can profoundly affect prenatal development. (C) 2016 Elsevier Inc. All rights reserved.