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Purpose: The International Lamotrigine Pregnancy Registry monitored for a signal of a substantial increase in the frequency of major congenital malformations associated with lamotrigine exposures in pregnancy over an 18-year period. Key methodological lessons are discussed., Methods: The strengths and weaknesses of the Registry were assessed using quantifiable methodological and operational parameters including enrollment, completeness of exposure and outcome data reporting, and lost to follow-up. The choice of comparator groups and stopping rules for registry closure were critically evaluated., Results: The reliance on voluntary reporting was associated with a clustered geographical distribution of registered pregnancies. The enrollment rate increased over time with new approvals and indications for lamotrigine and publication of interim data. Reporter burden was minimized through a streamlined data collection approach resulting in a high level of completeness of exposure and primary outcome data. Lost to follow-up rates were high (28.5% overall) representing a major limitation; incentives to increase the completeness of reporting failed to reduce rates. A lack of an internal comparator group complicated data interpretation; but external comparisons with multiple external groups allowed an assessment of consistency of outcome data across multiple data sources. A lack of a priori closure criteria prolonged the life of the Registry, and consideration of regulatory guidelines on this subject is encouraged at the time of conception of future registries., Conclusions: A successful pregnancy exposure registry requires ongoing flexibility and continuous re-assessment of enrollment, recruitment, and retention methods and the availability of comparison data, throughout its lifecycle., (Copyright © 2014 John Wiley & Sons, Ltd.)

Objective: To monitor for a signal for major teratogenicity following in utero lamotrigine exposure., Methods: Health care providers reported lamotrigine exposure during pregnancy, and subsequent outcomes, on a voluntary basis. Prospective reporting early in pregnancy was encouraged. Major congenital malformations (MCMs) were classified according to the Centers for Disease Control and Prevention (CDC) criteria and were reviewed by a pediatrician on the Registry's Scientific Advisory Committee. The proportion of infants with MCMs was calculated by trimester and therapy type and descriptively compared to population-based reference estimates., Results: Over an 18-year period, 35 infants with MCMs were observed among 1,558 first-trimester monotherapy exposures: 2.2%(95% confidence interval [CI] 1.6%-3.1%). This was similar to estimates from general population-based cohorts. The observed proportion of infants with MCMs among 150 lamotrigine/valproate polytherapy exposures was 10.7% (95% CI 6.4%-17.0%) and was 2.8% (95% CI 1.5%-5.0%) among 430 infants exposed to lamotrigine polytherapy without valproate. No consistent pattern of malformation type, or malformation frequency by dose, was observed., Discussion: The Registry did not detect an appreciable increase in MCM frequency following first-trimester lamotrigine monotherapy exposure. With over 1,500 first-trimester monotherapy exposures, the Registry was powered to detect major teratogenicity. The proportion of infants with MCMs following lamotrigine/valproate polytherapy exposure was high, but similar to that previously reported with valproate monotherapy. The Registry failed to observe an increased MCM frequency with increasing lamotrigine dose. Monitoring of specific malformations among lamotrigine-exposed pregnancies will continue through case-control surveillance in the European Congenital Anomalies and Twins Registers network.

Data from the International Lamotrigine Pregnancy Registry were analyzed to examine the effect of maximal first-trimester maternal dose of lamotrigine monotherapy on the risk of major birth defects (MBDs). Among 802 exposures, the frequency of MBDs was 2.7% (95% confidence interval [CI] 1.8-4.2%). The distribution of dose did not differ between infants with and those without MBDs (mean 248.3 milligrams per day [mg/day] and 278.9 mg/day, respectively, median 200 mg/day for both groups). A logistic regression analysis showed no difference in the risk of MBDs as a continuous function of dose (summary odds ratio [OR] per 100 mg increase =0.999, 95% CI 0.996-1.001). There was also no effect of dose, up to 400 mg/day, on the frequency of MBDs.

Objective: To report the frequency of major malformations in lamotrigine-exposed pregnancies from September 1, 1992, through March 31, 2004, in the International Lamotrigine Pregnancy Registry., Methods: Health care professionals throughout the world can voluntarily enroll lamotrigine-exposed pregnancies in this observational study. Only pregnancies with unknown outcomes at the time of enrollment were included in the analysis. The percentage of outcomes with major birth defects was calculated as the total number of outcomes with major birth defects divided by the sum of the number of outcomes with major birth defects + the number of live births without defects., Results: Among 414 first-trimester exposures to lamotrigine monotherapy, 12 outcomes with major birth defects were reported (2.9%, 95% CI 1.6% to 5.1%). Among the 88 first-trimester exposures to lamotrigine polytherapy including valproate, 11 outcomes with major birth defects were reported (12.5%; 95% CI 6.7% to 21.7%). Among 182 first-trimester exposures to lamotrigine polytherapy excluding valproate, 5 outcomes with major birth defects were reported (2.7%, 95% CI 1.0% to 6.6%). No distinctive pattern of major birth defects was apparent among the offspring exposed to lamotrigine monotherapy or polytherapy., Conclusions: The risk of all major birth defects after first-trimester exposure to lamotrigine monotherapy (2.9%) was similar to that in the general population and in other registries enrolling women exposed to antiepileptic monotherapy (3.3% to 4.5%). However, the sample size was too small to detect any but very large increases in specific birth defects.