Recreational use of marijuana during pregnancy and negative gestational and fetal outcomes: An experimental study in mice.

The prevalence of marijuana use among pregnant women is high. However, the effects on gestation and fetal development are not well known. Epidemiological and experimental studies present conflicting results because of the route of administration, dose, time of exposure, species used, and how Cannabis toxicity is tested (prepared extracts, specific components, or by pyrolysis). In this study, we experimentally investigated the effects of maternal inhalation of Cannabis sativa smoke representing as nearly as possible real world conditions of human marijuana use. Pregnant mice (n=20) were exposed (nose-only) daily for 5min to marijuana smoke (0.2g of Cannabis) from gestational day (GD) 5.5 to GD17.5 or filtered air. Food intake and maternal weight gain were recorded. Ultrasound biomicroscopy was performed on 10.5 and 16.5dpc.On GD18.5, half of the dams were euthanized for the evaluation of term fetus, placenta, and resorptions. Gestation length, parturition, and neonatal outcomes were evaluated in the other half. Five minutes of daily (low dose) exposure during pregnancy resulted in reduced birthweight, and litter size was not altered; however, the number of male pups per litter was higher. Besides, placental wet weight was increased and fetal to placental weight ratio was decreased in male fetuses, showing a sex-specific effect. At the end of gestation, females from the Cannabis group presented reduced maternal net body weight gain, despite a slight increase in their daily food intake compared to the control group. In conclusion, our results indicate that smoking marijuana during pregnancy even at low doses can be embryotoxic and fetotoxic.