Transplacental exposure to antipsychotic drugs during pregnancy and megacystis in the fetus.

Urinary retention is an adverse effect of antipsychotic drugs that has not been previously reported in the fetus. We have diagnosed megacystis in a fetus possibly caused by transplacental exposure to the antipsychotic drugs being administered to the mother. Two weeks after the mother stopped taking the drugs, the size of the enlarged fetal urinary bladder returned to normal. Sonographic examination of the neonate revealed an anatomically normal urinary tract, with a normal bladder capacity and urination.