Effect of valproic acid on fetal and maternal organs in the mouse: a morphological study.

Valproic acid (VPA) is an antiepileptic drug used clinically. Because of its known teratogenic properties VPA is not recommended for women of child bearing age. The present study was designed to assess the effects of VPA on both fetal and maternal organs. Randomized groups of pregnant mice were treated as follows: Group 1 (n = 10) 500 mg/kg VPA/day on gestation days 8-11; Group 2 (n = 10) 600 mg/kg VPA/day on gestation days 8-11; and Group 3 (n = 4) saline-injected controls. On gestation day 18, the pregnant mice were euthanized, fetuses collected and prepared for scanning electron microscopy. In addition, fetal and maternal organs were processed for routine histology, immunohistochemistry for growth factors (TGF alpha, beta-1, beta-2 and EGF) and transmission electron microscopy. Scanning microscopy revealed specific lesions induced by VPA in the fetus, namely spina bifida occulta, exencephaly, and exophthalmia. On the other hand, there were no detectable morphological changes in fetal or maternal organs by routine histology, immunohistochemistry or electron microscopy. The data suggest that the lesions present in the fetus are due to a direct effect by VPA on retinoic acid, a ubiquitous compound that has a role in normal development, rather than the lack of transport of sufficient nutrients to the fetus as a result of placental insufficiency due to VPA-induced toxicity.