In a study of female patients with epilepsy, retrospective data found that unintended pregnancy was common and varied by contraceptive type and antiepileptic drug (AED) stratification. Full findings are published in Neurology.

Andrew G. Herzog, MD, from the Harvard Neuroendocrine Unit, Boston, MA, and colleagues reviewed retrospective data from the Epilepsy Birth Control Registry (EBCR) web-based survey. A total of 1,144 women with epilepsy aged 18-47 years with epilepsy, AED, contraceptive, and pregnancy data were included. In the survey, participants indicated whether pregnancies were intended or unintended including the type of contraceptive and AED used at conception. Study authors also reported failure rates relative to the frequency of use of each contraceptive category in the registry. 

Most women with epilepsy (78.9%) indicated having at least one unintended pregnancy and more than half (65%) of their pregnancies were unintended. Unintended pregnancy was more frequent among younger, racial minority, and Hispanic women with epilepsy.  

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Intrauterine devices had the lowest failure rate among the reversible contraceptive categories. The failure rates also differed between systemic hormonal contraceptives based on whether oral or non-oral formulations were used and the type of concomitant AED the patient was on.

Oral contraceptives in general had a higher failure rate than non-oral contraceptives. Moreover, hormonal contraceptives combined with enzyme-inducing AEDs were associated with a substantially higher failure rate than hormonal contraceptives combined with no AED or any other AED category and in comparison to barrier plus any AED category. Other combinations of AED-hormonal contraceptive had lower risks than barrier. 

Dr. Herzog added, “In view of the important consequences of unintended pregnancy on pregnancy outcomes, these retrospective findings warrant further prospective investigation.”

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