Hypertension arising after 20 weeks of gestation: gestational hypertension or masked chronic hypertension?

Abstract Objectives the aims were 1- to evaluate the prevalence of masked chronic hypertension in pregnant women classified as gestational hypertension 2- to compare the risks of developing preeclampsia in true gestational hypertension vs those women classified as having gestational hypertension but who had had masked hypertension in the first half of pregnancy. Methods We conducted a cohort study in consecutive high-risk pregnancies who were evaluated before 20 weeks of gestation. Women who developed hypertension (office BP ≥ 140/90 mmHg and/or antihypertensive treatment) after 20 weeks of gestation was classified, according to the ABPM performed before 20 weeks of gestation, as having “true” gestational hypertension (if their ABPM before 20 weeks of gestation was normal) or “pseudo” gestational hypertension (if they had masked chronic hypertension). Risks for preeclampsia (PE) were estimated and compared with normotensive women. Results Before 20 weeks of gestation, 227 were analyzed (age 32 ± 6 years, median gestation age 15 weeks); 67 had chronic hypertension (29.5%). Of the remaining 160, 39 developed gestational hypertension (16 had true gestational and 23 pseudo gestational hypertension, because they had masked hypertension in the first half of pregnancy). Compared with normotensive pregnant women, true gestational hypertension did not increase the risk of developing PE (OR = 0.76, 95%CI = 0.16–6.65). Conversely, pseudo gestational hypertension increased the risk of PE more than 4 times (0R = 4.47 CI = 1.16–12.63). Risk estimation did not change substantially after the adjustment for multiple possible confounders. Conclusion 59% of women diagnosed as gestational hypertensives had indeed masked chronic hypertension and a high risk of developing PE.