Predictors of unintended pregnancy in women with epilepsy.

OBJECTIVE: To determine whether rates of unintended pregnancy in women with epilepsy (WWE) vary by contraceptive category and when stratified by antiepileptic drug (AED) category.

METHODS: These retrospective data come from the Epilepsy Birth Control Registry (EBCR) web-based survey of 1,144 WWE in the community, 18-47 years of age, who provided demographic, epilepsy, AED, contraceptive, and pregnancy data. Participants indicated whether pregnancies were intended or unintended, as well as the type of contraceptive and AED used at conception. We report failure rates relative to the frequency of use of each contraceptive category in the EBCR.

RESULTS: Most WWE (78.9%) reported having at least one unintended pregnancy; 65.0% of their pregnancies were unintended. Unintended pregnancy was more common among younger, racial minority, and Hispanic WWE. Among reversible contraceptive categories, the intrauterine device had the lowest failure rate. Failure rates varied greatly on systemic hormonal contraception (HC), depending on whether oral or nonoral forms were used and especially in relation to the category of AED with which HC was combined. Oral forms had greater failure rate than nonoral forms. HC combined with enzyme-inducing AEDs had a substantially greater failure rate than HC combined with no AED or any other AED category and in comparison to barrier plus any AED category. Other AED-HC combinations, in contrast, carried lower risks than barrier.

CONCLUSIONS: Unintended pregnancy is common among WWE and may vary by contraceptive category and AED stratification. In view of the important consequences of unintended pregnancy on pregnancy outcomes, these retrospective findings warrant further prospective investigation.