LAUSR

Key Points • Traditionally, in studies using healthcare utilization databases, investigators identify pregnancies starting from their outcome and calculate the first day of the last menstrual period (LMP) by subtracting the estimated gestational age from the date of delivery. • The relatively new ICD-10-CM Z3A codes, which indicate the gestational age at the time of the encounter, can be used for a potentially more precise LMP estimation than ICD-9-CM codes supported. • In an article recently published in PDS, Bertoia and colleagues put forward an algorithm that allows prospective identification of pregnancies in US claims by using ICD-10-CM Z3A codes. • Other research groups have developed related approaches that can identify ongoing pregnancies. • In addition to providing an up-to-date description of the basics of pregnancy-identification methods using existing healthcare data sources, we critically review advantages and challenges of these approaches.