Table 1. Main Differences in the Design and Analytic Approach Between the US and Nordic Analyses.

Study Characteristic	US Study	Nordic Study
Cohort	Live births	Live singleton births
Exclusions	Known teratogens	Gestational wk ≤22 or >44
		Birth weight <300 or >7000 g
Exposure window	First trimester: LMP to LMP + 90 d	First trimester: LMP to LMP + 97 d
Reference group	No exposure from 3 mo before LMP to LMP + 90 d	No exposure from LMP to LMP + 97 d
Outcome assessment	First 3 mo of life	First year of life, except Norway (first 3 mo of life)
Covariate assessment	ICD-9	ICD-9 and ICD-10
	3 mo before LMP to LMP + 90 d	Maternal nonpsychiatric: 1 y before LMP to delivery
	Healthcare utilization: 3 mo before LMP to LMP	Maternal psychiatric: 5 y before LMP to delivery
		Concomitant drug use: 90 d before LMP to LMP + 97 d
Confounding adjustment	Fine stratification on the propensity score	Multivariate regression

Abbreviations: ICD-9, International Classification of Diseases, Ninth Revision; ICD-10, International Classification of Diseases, Tenth Revision; LMP, last menstrual period.