Concentration of valproate during pregnancy, in the newborn and in breast milk.

The serum-valproate level of four patients with epilepsy was followed during pregnancy. A decrease in serum level occurred late in pregnancy and was followed by a pronounced increase in the first week after delivery. The maternal serum concentration of valproate was compared to that of the umbilical cord. The level in cord blood was 145-219% higher than that in maternal blood. The concentration of valproate in breast milk was found to be 5-10% of the maternal serum concentration. The serum concentration was measured in one breastfed child. The level was 7.6% of the maternal serum concentration. All children were healthy without any signs of intoxication or malformation. Based on our experience, pregnant patients treated with valproate must be carefully controlled especially during the last month of pregnancy and in the first two weeks after delivery. The amount of valproate excreted into the breast milk was negligible and should not prevent breast feeding.