Placental transfer of atropine at the end of pregnancy.

In a first study, 28 pregnant women received a fast intravenous injection of atropine sulphate 12.5 microgram/kg, as in a classical atropine test. Fetal tachycardia resulted. The maternal venous blood concentration of atropine, determined by bioassay on guinea pig ileum, decreased rapidly in the first 3--5 min and very slowly therafter. In a second study, 45 women in labour received the same dose i.v., and at birth atropine was measured both in maternal and cord blood. Placental transfer of atropine had occurred in every case and was highly variable, depending on the maternal blood concentration of the drug. This suggests that the atropine test is not mainly dependent on placental function.