White coat hypertension in early pregnancy in women with pre-existing diabetes: prevalence and pregnancy outcomes
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Hypertensive disorders are prevalent among pregnant women with pre-existing diabetes, but the prevalence and impact of white coat hypertension are unknown. Measurement of home BP before initiation of antihypertensive treatment is necessary to identify white coat hypertension since international guidelines recommend that white coat hypertension is left untreated. The aim of this study, conducted among women with pre-existing diabetes, was therefore to examine the prevalence of white coat hypertension in early pregnancy, and pregnancy outcome in women with white coat hypertension in early pregnancy.
A prospective cohort study was undertaken involving women with pre-existing diabetes from a geographically well-defined area. Based on office BP in early pregnancy and home BP measured for 3 days, women were categorised in three groups: (1) white coat hypertension, defined as office BP ≥ 135/85 mmHg and mean home BP < 130/80 mmHg; (2) chronic hypertension, defined as pre-pregnancy hypertension including newly detected office BP ≥ 135/85 mmHg with home BP ≥ 130/80 mmHg; and (3) normotension. Office BP was measured every 2 weeks and, if ≥ 135/85 mmHg, home BP measurements were performed. White coat hypertension was left untreated, and tight antihypertensive treatment was initiated when both office BP ≥ 135/85 mmHg and home BP ≥ 130/80 mmHg. Pregnancy-induced hypertensive disorders were defined as office BP ≥ 140/90 mmHg with home BP ≥ 130/80 mmHg when available, with onset after 20 weeks of gestation.
In total, 32 out of 222 women with pre-existing diabetes had newly detected office BP ≥ 135/85 mmHg in early pregnancy. White coat hypertension was present in 84% (27/32) of these women, representing 12% (95% CI 8%, 17%) of the whole cohort. Chronic hypertension was present in 14% (n = 32) and normotension in 74% (n = 163). Women with white coat hypertension were characterised by higher pre-pregnancy BMI (p = 0.011), higher home BP (p < 0.001) and higher prevalence of type 2 diabetes (p = 0.009), but similar HbA1c (p = 0.409) compared to women with normotension. Regarding pregnancy outcome, pregnancy-induced hypertensive disorders developed in 44% (12/27) of women with white coat hypertension in comparison with 22% (36/163) among initially normotensive women (p = 0.013), while the prevalence of preterm delivery was comparable (p = 0.143). The adjusted analysis, performed post hoc, suggested approximately double the risk of developing pregnancy-induced hypertensive disorders (OR 2.43 [CI 0.98, 6.05]) if white coat hypertension was present in early pregnancy, independently of pre-pregnancy BMI and parity.
White coat hypertension is prevalent in women with pre-existing diabetes and may indicate a high risk of later development of pregnancy-induced hypertensive disorders. To distinguish between persistent white coat hypertension and onset of pregnancy-induced hypertension, repeated home BP monitoring is recommended when elevated office BP is detected.
The study was registered at ClinicalTrials.gov (ID: NCT02890836).
KeywordsAspirin Diabetes Home blood pressure Hypertension Preeclampsia Pregnancy Pregnancy-induced hypertensive disorders Pregnancy outcome White coat hypertension
Large for gestational age
Neonatal intensive care unit
Small for gestational age
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The authors are grateful to research-midwife M. A. Mikkelsen (Center for Pregnant Women with Diabetes, Rigshospitalet, Denmark) and A. Boa (Department of Obstetrics, Odense University Hospital, Denmark) for help with recruitment, collection and handling of data. Thanks to the nurses at the Center for Pregnant Women with Diabetes, Rigshospitalet, Denmark, for help with recruitment. We also thank the pregnant women for their time and interest in the study.
The overall initiative for the study was taken by ERM, PD and MV. MV and BA collected the data. All co-authors contributed to the conception of the study, the analysis and interpretation of data. MV performed the statistical analysis and prepared the first draft of the manuscript. All co-authors revised the manuscript critically for important intellectual content. MV collected all comments from the co-authors and prepared the final draft. All co-authors approved the final version to be published. ERM is the guarantor of this work.
MV was funded by Rigshospitalet’s Research Foundation. ERM was funded by Novo Nordisk Foundation (grant no. NNF14OC0009275).
Duality of interest
The authors declare that there is no duality of interest associated with the manuscript.
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