Plasma delta-9-tetrahydrocannabinol in pregnant sheep and fetus after inhalation of smoke from a marijuana cigarette.

Seven pregnant ewes were prepared with open-ended tracheal T tubes and with catheters in maternal femoral artery and in central circulation of fetus. Several days postoperatively, at 129-132 days gestation, ewes inhaled smoke from one marijuana cigarette containing 3.19% delta-9-tetrahydrocannabinol (delta-9-THC). Smoke was produced continuously in a hand-held chamber and delivered to the protruding arm of the tracheal tube. Samples of maternal and fetal blood were taken during the 8-10 minute smoking period and at intervals up to 24 hours. Delta-9-THC was detected in maternal plasma at 3 minutes and peaked at 10 minutes. Fetal plasma delta-9-THC reached detectable levels in 5 animals by 10 minutes. Maximum mean level was reached at 90 minutes and remained nearly constant until the fourth hour. Fetal delta-9-THC levels remained lower than maternal levels at all times. The terminal half-life of delta-9-THC in fetal and maternal plasma exceeded 10 hours.