Hormonal contraception had a relative risk for unintended pregnancy of 4.94 (P <.0001) compared with intrauterine devices, which had the lowest rate (3.1%). Oral forms of hormonal contraception had a higher risk compared with non-oral forms (RR: 2.89, P <.0001), and combined oral contraceptives had a higher risk compared with implanted progestin (RR: 7.34, P =.04).
When data were analyzed based on the AED-contraceptive combination, the combination of enzyme-inducing AEDs with hormonal contraception had the highest relative risk of unintended pregnancy (RR: 2.35, P =.01). Further, WWE taking enzyme-inducing AEDs accounted for 60.7% of all unintended pregnancies in participants on hormonal contraception.
“In view of the important consequences of unintended pregnancy on pregnancy outcomes, healthcare providers should be familiar with the reciprocal interactions that exist between a number of antiepileptic drugs and hormonal contraception and, in particular, that the risk of unintended pregnancy may double when combining hormonal contraception with enzyme-inducing antiepileptic drugs,” Dr Herzog said.
In an accompanying editorial, Kimford J. Meador, MD, of the Stanford Neuroscience Health Center in Palo Alto, California and Dick Lindhout, MD, PhD, of the University Medical Center Utrecht and Stichting Epilepsie Instellingen Nederland, in The Netherlands, wrote that despite the study’s limitations, including the use of retrospective data and self-reported outcomes, the results were “striking.”3