Purpose: Accurate measurement of medication exposure is crucial for studying the safety of antiseizure medications (ASMs) during pregnancy. Pregnancy safety studies of ASMs frequently rely on secondary data from drug prescription registries to assess potential teratogenic effects and impact on fetal development. This study aimed to evaluate the agreement between dispensed prescriptions registered in a national database and self-reported ASM use by parents.
Methods: The Norwegian Prescription Database (NorPD) was linked to the Norwegian Mother, Father, and Child Cohort Study (MoBa) and the Medical Birth Registry of Norway (MBRN). Participants included mothers and fathers in the MoBa-study between 2004 and 2009. Agreement between dispensed ASM prescriptions and self-reported use was assessed by calculating Cohen's kappa (κ), sensitivity, and specificity, with self-reported use as the reference standard.
Results: A total of 40 632 pregnant women and 42 247 fathers were included. Maternal dispensed ASM prescriptions during pregnancy showed strong overall agreement (κ = 0.81) with self-reported use, with a sensitivity of 80.6% and specificity of 99.9%. Paternal dispensed ASM prescriptions up to 7 months prior to conception also demonstrated strong agreement (κ = 0.81) with self-reported use. Analysis of individual ASMs revealed varying reliability: levetiracetam and lamotrigine had the highest agreement among maternal (κ = 0.92) and paternal (κ = 0.92) dispensed prescriptions, respectively.
Conclusion: There is strong agreement between dispensed ASM prescriptions and self-reported medication use by parents, supporting the use of prescription data for evaluating the risks of ASM use during pregnancy.
Keywords: antiseizure medications; exposure misclassification; pregnancy; teratology; validity.
© 2025 The Author(s). Pharmacoepidemiology and Drug Safety published by John Wiley & Sons Ltd.