Rats were treated orally with ayahuasca (AYA) on gestation days (GD) 6-20 at doses corresponding to one-(1X) to eight-fold (8X) the average dose taken by a human adult in a religious ritual, and the pregnancy outcome evaluated on GD21. Rats treated with 4X and 8X doses died during the treatment period (44 and 52%), and those that survived showed kidney injury. Rats surviving the 8X dose showed neuronal loss in hippocampal regions and in the raphe nuclei, and those from the 2X dose neuronal loss in CA1. Delayed intrauterine growth, induced embryo deaths and increased occurrence of foetal anomalies were observed at the 8X dose. At non-lethal doses, AYA enhanced embryolethality and the incidence of foetal soft-tissue and skeleton anomalies. This study suggested that AYA is developmentally toxic and that its daily use by pregnant women may pose risks for the conceptus.