Differential risks of changes in seizure frequency with transitions between hormonal and non-hormonal contraception in women with epilepsy: A prospective cohort study.

This prospective, observational, cohort study of 101 women with epilepsy (WWE) assesses the seizure safety of systemic hormonal contraception (HC) versus non-HC (NHC). It reports risks of changes in seizure frequency associated with transition from NHC to HC relative to HC to NHC for (1) proportions of WWE with ≥50% increase and decrease in seizure frequency, (2) changes in seizure frequency, (3) changes in seizure severity, and 4) changes in AED regimen during the study. In comparing NHC to HC versus HC to NHC, NHC to HC had greater risk of ≥50% increase in seizure frequency: RR = 1.98 (1.07-3.64), p = 0.03 and lower risk of ≥50% decrease in seizure frequency: RR = 0.42 (0.22 = 0.83), p = 0.01. These risks were particularly notable for oral contraceptive pill: RR = 2.91 (1.26-6.72), p = 0.01 and RR = 0.54 (0.30-0.97), p = 0.04, respectively. Median monthly seizure frequency (MMSF) increased 302.0% (p = 0.0019) with transition from NHC to HC. MMSF decreased 81.9% with change from HC to NHC (p = 0.001). RR for change in seizure type from milder to more severe type was greater for NHC to HC: RR = 3.32 (1.07-10.27), p = 0.04. Change in AED regimen was not a significant factor. The findings suggest further prospective study to assess whether HC, especially oral contraceptive pill, poses a greater risk of increased seizures than NHC.