Validation of ICD-10-CM Diagnosis Codes for Gestational Age at Birth

Abstract

The International Classification of Diseases Clinical Modification 10th Revision (ICD-CM-10) introduced diagnosis codes for week of gestation at delivery (8-42 weeks). Our objective was to assess the validity of these codes, which could have major utility in perinatal research and quality improvement. We used linked birth certificate and hospitalization discharge data from all live births in California during 2016-2019 (N = 1,843,992). Gestational age was identified using Z3A.xx ICD-10-CM diagnosis codes in maternal patient discharge data and compared with the gold standard of best obstetric estimate, as recorded on the birth certificate. We further assessed sensitivity and specificity of gestational age categories (< 37 weeks, < 32 weeks, < 28 weeks) given these categories are frequently of interest. We excluded records with gestational age < 20 or >42 weeks or if missing (3.9%). 1,771,527 patients had gestational age recorded on the birth certificate and in the hospitalization discharge data. When comparing gestational age in patient discharge data with birth certificate data, the mean of the difference was -0.32 days (SD=3.80) and the R2 value was 0.92. 95% of observed differences between pairs of gestational age measurements were between -7.14 to +7.77 days, and 99.3% of differences were within +/-14 days. The sensitivity, specificity, positive predictive value, and negative predictive value were all high for the three gestational age categories, although the positive predictive value did decrease with earlier gestational age category (Table). Week-specific gestational age at delivery diagnosis codes in patient discharge data were found to have high validity when compared with the gold standard of best obstetric estimate on the birth certificate. The introduction of these codes with the implementation of ICD-10-CM in 2015 is promising for research and quality improvement purposes.