Association Between Maternal Glucose Levels in Gestational Diabetes Screening and Subsequent Hypertension

Abstract

BACKGROUND: We assessed the association between maternal glucose levels in pregnancy and subsequent hypertension. METHODS: This population-level, retrospective cohort study examined women aged 12 to 54 years with singleton pregnancies completed at ≥29 weeks of gestation from October 1, 2008 to December 1, 2018 followed until March 31, 2019 in Alberta, Canada. Women were stratified by results in the 50-gram glucose challenge test and by 75-gram oral glucose tolerance test subtypes (normal oral glucose tolerance test, elevated fasting plasma glucose only [elevated fasting], elevated postload glucose only, or both elevated fasting and postload glucose [combined]. Time to development of hypertension was modeled using Cox proportional hazards models. RESULTS: Of 313 361 women, 231 008 (79.1%) underwent a glucose challenge test only while 60 909 (20.9%) underwent either an oral glucose tolerance test only or both. Nine thousand five hundred eighty (3.1%) developed hypertension, and 2824 (0.9%) developed cardiovascular disease over a median follow-up of 5.7 years. Every 1-mmol/L increase in glucose in the glucose challenge test increased the risk of subsequent hypertension by 15% (adjusted hazard ratio and 95% CI, 1.15 [1.14–1.16]). Among those who underwent the oral glucose tolerance test, the combined group conferred the highest risk of subsequent hypertension, followed by elevated fasting, then elevated postload glucose only (reference: glucose challenge test ≤7.1 mmol/L, adjusted hazard ratio [95% CI]: elevated postload glucose only, 1.83 [1.68–2.00]; elevated fasting 2.02 [1.70–2.40]; combined, 2.65 [2.33–3.01]). No significant associations between maternal glucose levels and cardiovascular disease were observed. CONCLUSIONS: Increasing maternal glucose levels in pregnancy were associated with increasing risk of subsequent hypertension. These findings may help identify higher-risk women who should be targeted for earlier postpartum cardiovascular risk reduction.