Hypertensive disorders in a gestational diabetes cohort from Cape Town, South Africa

As thresholds for the diagnosis of gestational diabetes mellitus (GDM) become lower, and the prevalence of obesity in society rises, more pregnant women will be diagnosed with GDM and hypertension. Both conditions hold dangers for mother and baby. Our objective was to properly describe this association.

This retrospective audit was conducted at the Obstetric High-Risk Clinic at Tygerberg Academic Hospital, Cape Town, South Africa. All patients diagnosed with GDM from 01/01/19 - 31/12/19 were included. The primary aim was to determine the incidence, and different classes of hypertensive disease associated with GDM in this population. The secondary aims were to evaluate associations with the development of hypertensive disorders in women with GDM and to include descriptions of the management, course and complications during the pregnancies, including the early neonatal period. The research was approved by the Ethics Committee of Stellenbosch University.

Of the 274 women with GDM, included in the analysis, 204 (75 %) had concomitant hypertension. Classes of hypertension were chronic hypertension 21 % (58/274), gestational hypertension 26 % (71/274), and pre-eclampsia (de novo and super-imposed) 27 % (75/275). Those without hypertension had significantly lower BMIs: 35 [29-42] vs 41 [34-45] kg/m² (median [IQR]; p < 0.001). Using ROC curves, BMI at booking had strong associations with chronic and gestational hypertension (p = 0,002; p = 0,001), and pre-eclampsia (p = 0,002). All three intra-uterine deaths (two spontaneous and one iatrogenic) occurred in the GDM + hypertension group.

Hypertensive conditions of pregnancy were common amongst a referral-based population with GDM, with BMI being the strongest predictor.