Purpose To examine movements in fetuses of women taking the anti-epileptic drugs carbamazepine, valporate and lamotrigine and to compare them to unaffected fetuses.

Method Fetuses of thirty women taking three anti-epileptic drugs (carbamazepine: n=10; valporate: n=10; lamotrigine: n=10) and of 20 women unaffected by epilepsy were studied. Fetal movements were observed by ultrasound for 30 min at 12–15 weeks gestation. The number of arm, leg, startle and head movements was recorded off-line for each fetus.

Results Results revealed more movement by fetuses in the carbamazepine group (M=9.62 +/−3.15 (SD)) and less movement by fetuses in the valporate group (M=6.06 +/−2.37) than by those in the control group (M=6.96 +/−3.01, n=20). Movement scores of fetuses in the lamotrigine group (M=7.75 +/−3.03, n=7) were similar to those in the control group.

Fetal activity is affected by anti-epileptic drugs, and these effects are drug-specific. Anti-epileptic medications have been associated with cognitive delay in children. Observation of fetal behaviour reveals the effect of these medications on central nervous system functioning during the prenatal period. Evaluation of fetal behaviour may enable the mechanisms by which anti-epileptic drugs exert their long term neurodevelopmental consequences to be determined.