A paucity of information is available concerning the use of levodopa and carbidopa during pregnancy. Particularly lacking is whether these agents cross the placenta and whether levodopa undergoes metabolism in the fetus. The present study carried out in aborted fetal tissues demonstrates that levodopa crosses the placental barrier and suggests that it may be metabolized in fetal tissues, including the brain and spinal cord. The possibility exists that early exposure to levodopa or dopamine may alter the normal neuronal development in the fetus, and caution in the use of levodopa during pregnancy should be observed.