Placental transmission of atropine at full-term pregnancy.

Measurements of placental transmission of atropine were performed during Caesarean section. Twenty-five patients received 3H-atropine 0.5 microgram . kg-1 i.v. 1-30 min before delivery. Maternal venous blood was sampled before the induction of anaesthesia and at the moment of delivery, together with umbilical arterial and venous blood. Total hydrogen-3 activity was determined by liquid scintillation counting. The stability of 3H-atropine was confirmed by paper chromatography. The concentrations in the umbilical vein 1 and 5 min after injection were respectively 12% and 93% of the corresponding maternal value. Those in the umbilical artery were approximately 50% of those in the umbilical vein during the same period.