Does gestational hypertension become pre-eclampsia?

OBJECTIVE: To determine the likelihood of progression from gestational hypertension (GH) to pre-eclampsia (PE) in hypertensive pregnant women and whether this change can be identified in advance by available clinical and laboratory measures.
DESIGN: A retrospective analysis and a prospective study.
SETTING: St George Hospital, Sydney, a teaching hospital of the University of New South Wales delivering 2500 women per year. POPULATION: Eight hundred and forty-five women with new hypertension in the second half of pregnancy, managed by a uniform protocol (661 in the retrospective analysis, 184 in the prospective study).
METHODS: Clinical and laboratory data at initial presentation were compared among women with GH who developed PE and those who remained with a diagnosis of GH until delivery. Data predictive for progression from GH to PE were analysed by logistic regression analysis. MAIN OUTCOME MEASURED: Progression from GH to PE.
RESULTS: In the retrospective analysis, 416 women initially presented as having GH and 62 (15%) progressed to PE. In the prospective study, 112 women initially presented with GH and 29 (26%) progressed to PE, giving an overall progression of 17%. In both studies, women who developed PE from GH presented earlier than those who remained with GH until delivery. In multiple logistic regression analyses prior miscarriage and early gestation at presentation were associated with increased likelihood of progressing from GH to PE.
CONCLUSION: Approximately 15-25% of women initially diagnosed with GH will develop PE and this is more likely with earlier presentation or if the woman has had a prior miscarriage. Women with gestational hypertension diagnosed after 36 weeks of gestation have only about 10% risk of developing PE. These data should help stratify the risks of mildly hypertensive pregnant women being managed as outpatients in their third trimester.