Abstracts

Rationale: Family planning is particularly important for women with epilepsy (WWE) because they are at increased risk of having offspring with major congenital malformations and risk may be mitigated by optimal seizure control on a minimum of antiepileptic drug (AED) at conception. The purpose of this study was to determine whether the rate of unintended pregnancy in WWE varies by contraceptive category and by contraceptive category stratified by AED category. Methods: These retrospective data come from the Epilepsy Birth Control Registry (EBCR) web-based survey of 1144 WWE in the community, ages 18-47 years, who provided demographic, epilepsy, AED and contraceptive data. Participants reported pregnancies and indicated whether they were intended or unintended, as well as what type of contraceptive and AED they used at conception. We report the relative risks (RR) of unintended pregnancy on the various categories of contraception, and when stratified by AED categories, relative to the frequency of use of each category by the EBCR population. Results: 78.9% of the WWE in the EBCR reported having at least one unintended pregnancy and 65.0% of their 804 pregnancies were unintended. Unintended pregnancy rate correlated inversely with age (Spearman's rho = -0.358, p < 0.001). They were more common for minority races than for Caucasians (RR = 1.22 [95% CI: 1.06-1.41], p = 0.005) and for Hispanic than non-Hispanic ethnicities (RR = 1.24 [95% CI: 1.08-1.42], p = 0.002). WWE who had a history of generalized convulsions were at greater risk as compared to WWE who had only partial seizures (RR = 1.20 [1.03-1.39]; p = 0.017). 175 occurred on no contraception. Among the reversible categories of contraception, IUD had the lowest failure rate (3.1%) (Table 1). Relative to IUD, barrier had a RR = 3.89 [1.83-8.29], p = 0.0004; hormonal (HC) had RR = 4.94 [2.35-10.39], p < 0.0001 and withdrawal had RR =5.74 [2.67-12.31], p < 0.0001. HC showed a trend for a higher risk for unintended pregnancy than barrier (RR = 1.26 [0.99-1.62], p = 0.06). HC did not differ significantly from withdrawal. The risk for unintended pregnancy on HC, however, varied greatly by the subcategories of HC and HC-AED combinations. Oral forms of HC had greater failure rate than non-oral forms (RR = 2.89 [1.95-4.28], p < 0.0001). HC combined with enzyme inducing AEDs, but not with other categories of AEDs, had a substantially and significantly greater failure rate than HC combined with no AED (RR = 2.70 [1.51-4.82], p = 0.0008) (Table 2). Note, enzyme inducing AED-HC was the only AED-HC combination that carried a greater risk on HC than on barrier. The combination of HC plus barrier was superior to HC alone but not as effective as IUD (RR = 2.77 [1.03-7.43], p = 0.04). Conclusions: This study finds a high rate of unintended pregnancy among WWE. The risk varies by contraceptive category, especially when stratified by AED categories. The combination of HC with enzyme inducing AEDs carries a particularly high risk. These high rates of unintended pregnancy and their potential negative consequences warrant prospective investigation. Funding: Epilepsy Foundation and Lundbeck