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

The objectives of this study 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. We conducted a cohort study in consecutive high-risk pregnancies who were evaluated before 20 weeks of gestation. Women who developed gestational hypertension (normotension in the office before 20 weeks of gestation and office BP ≥ 140/90 mmHg and/or antihypertensive treatment in the second half of gestation) were divided, according to an ABPM performed before 20 weeks of pregnancy, in two subgroups: subgroup 1-if their ABPM was normal, and subgroup 2-if they had masked chronic hypertension. Risks for preeclampsia (PE) were estimated and compared with normotensive women. Before 20 weeks of gestation, 227 women were evaluated (age 32 ± 6 years, median gestation age 15 weeks); 67 had chronic hypertension (29.5%). Of the remaining 160, 39 developed gestational hypertension (16 in subgroup 1 and 23 insubgroup 2. Compared with normotensive pregnant women, subgroup 1 of women with gestational hypertension did not increase the risk of developing PE (OR = 0.76, 95% CI = 0.16-6.65). Conversely, subgroup 2 of 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. In conclusion, the59% of women initially diagnosed as gestational hypertensive according to current recommendations had masked chronic hypertension and a very high risk of developing PE.