Influence of Enhanced Administrative Case‐Finding Strategies on Prevalence of Hypertensive Disorders of Pregnancy in Ontario: A Population‐Based Descriptive Study

BACKGROUND: Hypertensive disorders of pregnancy (HDP) are a leading global cause of maternal and fetal morbidity/mortality. Most estimates of HDP occurrence are reported for composite exposures of HDP or preeclampsia alone, with limited disaggregation by obstetrical subgroup (eg, multi-fetal deliveries). Consequently, our understanding of HDP prevalence and temporal trends remains limited, and methods for identifying specific diagnoses in administrative data remain underexamined. This population-based descriptive study assessed how enhanced administrative case-finding definitions influence prevalence estimates of HDP in pregnancy and postpartum. METHODS: Included were individuals aged ≥18 years discharged from an Ontario hospital following their first obstetrical delivery between April 1, 2002, and December 31, 2017. We calculated overall and annual prevalence estimates and assessed temporal trends for any HDP and major subtypes by case-finding definitions, stratified by plurality (singleton versus multi-fetal deliveries). RESULTS: Most subjects had a singleton first delivery (n=781 258; 98%); however, HDP was 2.2 to 2.4 times more prevalent in multi-fetal deliveries. When pre-pregnancy hypertension was considered during case-finding, HDP prevalence increased from 193.6 to 207.6 per 1000 multi-fetal deliveries and from 79.9 to 92.6 per 1000 singleton deliveries. Gestational hypertension was the most common diagnosis in both populations but was nearly twice as common in those who delivered a multiple gestation (94.4-100.0 versus 49.7-53.4 per 1000 deliveries). Prevalence trends differed by coding strategy and plurality. CONCLUSIONS: Although informative, data from discharge abstracts alone are insufficient for HDP surveillance, particularly for chronic hypertension in pregnancy. Validation studies should assess the accuracy of our case-finding definitions against suitable reference standards.