Prenatal exposure to Cannabis and fetal development

The purpose of these experiments was to determine the effects of Cannabis extracts on fetal development when administered to pregnant rabbits In doses calculated to approximate those that may be reached in human consumption. Two series of experiments were conducted using 84 New Zealand rabbits. They were treated with Cannabis extracts administered by gastric intubation or by subcutaneous administration from days 6-18 of gestation. The animals were sacrificed on day 29. During pregnancy, treated rabbits showed a lower mean gain in body weight than did the control animals. The mean weights of the fetuses treated with Cannabis extracts were lower than those of fetuses from control animals. The differences were statistically significant for rabbits receiving the equivalent of 3 and 5 mg/kg THC per day via the oral route (p < 0.01 and 0.05) and for rabbits receiving 5 mg/kg THC per day by the subcutaneous route (p < 0.001). The mean weights of the placentae of the treated animals were lower than those of the control animals (following oral administration, p < 0.05, and following subcutaneous administration, p < 0.01). Whereas these studies demonstrate: that Cannabis extracts are fetotoxic in the rabbit, there was no indication that treatment had increased the incidence of major malformation. However, the fetuses of the animals treated with cannabis extract showed an increased incidence of minor skeletal and visceral anomalies.