The internal control group in a register of antiepileptic drug use in pregnancy

Antiseizure medication use during pregnancy and neonatal growth outcomes: A systematic review and meta-analysis

AIMS

We aimed to systematically synthesize the current published literature on neonatal growth outcomes associated with antiseizure medication (ASM) use during pregnancy.

METHODS

We searched seven databases, from inception to 23 March 2022. We investigated small for gestational age (SGA) and low birth weight (LBW) as primary outcomes and birth weight, birth height, cephalization index and head circumference as secondary outcomes. The primary analysis included pregnant people exposed to any ASM compared with unexposed pregnant people. Subgroup analysis included ASM class analysis, within epilepsy group analysis and polytherapy compared to monotherapy.

RESULTS

We screened 15 720 citations and included 65 studies in the review. Exposed pregnant people had a significantly increased risk of SGA relative risk (RR) 1.33 (95% CI 1.18 to 1.50, I2 74%), LBW RR 1.54 (95% CI 1.33 to 1.77, I2 67%), and decreased birth weight with a mean difference (MD) of -118.87 (95% CI -161.03 to -76.71, I2 42%) g. A non-significant risk change in birth height and head circumference was observed. In subgroup analysis, ASM polytherapy, within epilepsy and ASM class analysis were also associated with an increased risk of SGA and LBW.

CONCLUSIONS

This meta-analysis demonstrates that pregnant people exposed to ASMs have a significantly increased risk of adverse fetal growth outcomes including SGA and LBW and decreased birth weight compared to unexposed pregnant people. Polytherapy was associated with higher risks compared to monotherapy. Additional studies are warranted on specific ASM risks.

Effects of gestational age at enrollment in pregnancy exposure registries

PURPOSE

This study aims to explore the influence of gestational age at enrollment, and enrollment before or after prenatal screening, on the estimation of drug effects in pregnancy exposure registries.

METHODS

We assessed the associations between first trimester antiepileptic drug (AED) exposure and risk of spontaneous abortion and major congenital malformations in the North American AED Registry (1996-2013). We performed logistic regression analyses, conditional or unconditional on gestational age at enrollment, to estimate relative risk (RR) for first trimester AED users compared with non-users. We also compared first trimester users of valproic acid and lamotrigine. Analyses were repeated in women who enrolled before prenatal screening.

RESULTS

Enrollment occurred earlier among 7029 AED users than among 581 non-users; it was similar among AEDs. Comparing AED users with non-users, RR (95% confidence interval) of spontaneous abortion (n = 359) decreased from 5.1 (2.3-14.1) to 2.0 (0.9-5.6) after conditioning on gestational week at enrollment and to 1.9 (0.8-5.4) upon further restriction to before-screening enrollees. RR of congenital malformations (n = 216) changed from 3.1 (1.4-8.5) to 3.2 (1.4-9.0) after conditioning on gestational week at enrollment and to 2.0 (0.7-10.1) upon further restriction to before-screening enrollees. When comparing valproic acid users and lamotrigine users, the RR of congenital malformations was not substantially changed by conditioning or restricting.

CONCLUSIONS

Spontaneous abortion rates were sensitive to gestational age at enrollment. Estimates of congenital malformation risks for AED users relative to non-users were sensitive to before/after-screening enrollment. This difference was not apparent between active drugs, likely due to similar gestational age at enrollment.