38 Background: The associations of individual antiepileptic drugs (AEDs) with pregnancy duration 39 and size at birth, and potential dose relations, are not well characterized.40 Methods: This cohort study used nationwide Swedish register data (1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012)(2013). Adjusting for 41 smoking, epilepsy and other AED indications, we used linear and quantile regression to explore 42 associations with pregnancy duration, and birth weight, length, and head circumference (the last 43 three operationalized as z-scores). We used logistic regression for preterm delivery, small for 44 gestational age, and microcephaly. Lamotrigine was the reference drug.45 Results: 6,720 infants were exposed to AEDs in utero; AED exposure increased over the study 46 period. Relative to lamotrigine-exposed infants, carbamazepine-exposed infants were born, on 47 average, 1.3 days earlier (mean [95% confidence interval]: -1.3 [-2.3 to -0.3]); were 0.1 standard 48 deviations (SDs) lighter (-0.1 [-0.2 to 0.0]); and had a head circumference that was 0.2 SDs 49 smaller (-0.2 [-0.3 to -0.1]). Pregabalin-exposed infants were born, on average, 1.1 days earlier (-50 1.1 [-3.0 to 0.8]); were 0.1 SDs lighter (-0.1 [-0.3 to 0.0]); and had the same head circumference. 51 Levetiracetam-exposed infants were born, on average, 0.5 days earlier (-0.5 [-2.6 to 1.6]); were 52 0.1 SDs lighter (-0.1 [-0.3 to 0.0]); and were 0.1 SDs smaller (-0.1 [-0.3 to 0.1]) in head 53 circumference. Valproic acid-exposed infants had, on average, the same duration of gestation 54 and birth weight z-score, but were 0.2 SDs smaller (-0.2 [-0.2 to -0.1]) in head circumference. 55 More negative associations at the left tail of pregnancy duration and birth weight z-score, effect-56 measure modification, and dose-response relations were noted for some of the associations.57 Observed associations were generally of smaller magnitude than that of smoking, assessed as a 58 potential confounder in the same models. 4 59 Conclusions: In comparison with lamotrigine, valproic acid and carbamazepine had a more 60 negative association with head circumference than other study AEDs.
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INTRODUCTION63 Epilepsy and antiepileptic drugs (AEDs) have been associated with adverse pregnancy, fetal, and 64 neonatal outcomes [1]. AEDs differ in their risk for congenital malformations [2][3][4], and some 65 associations have been found to be dose dependent [4][5][6]. Newer AEDs are generally considered 66 safer than the older drugs, with the possible exception of topiramate [7]. Antiepileptic drugs also 67 differ in the magnitude of their associations with adverse neurodevelopmental outcomes in the 68 offspring, which also appear to be dose dependent [8][9][10]. The exploration of indication and dose 69 is important because confounding by indication has been a concern and AED doses are often 70 higher in epilepsy than in other conditions [11]. 71 A meta-analysis has shown elevated point estimates for the association of AEDs...