Ramsay R E
J Clin Neurophysiol. 1987 Jan;4(1):23-5. doi: 10.1097/00004691-198701000-00002.
Increased seizure activity during pregnancy may result from two different effects: a dominant estrogenic effect early in pregnancy that directly affects the central nervous system lowering seizure threshold and a decrease of 50% or more in the plasma level of anticonvulsant drugs in some individuals late in pregnancy, resulting in loss of seizure control.