The natural history of white coat hypertension during pregnancy

OBJECTIVE: White coat hypertension (WCH) is a common phenomenon with a long term prognosis intermediate between those with true hypertension and true normotension. The natural history of this phenomenon throughout pregnancy remains unknown. We assessed the likelihood of women with an initial diagnosis of WCH developing pre-eclampsia (PE) as their pregnancy progressed. DESIGN: Prospective observational study. SETTING: St George Hospital, a teaching and University hospital. POPULATION: Two hundred and forty-one pregnant women with an early pregnancy diagnosis of essential hypertension (EH). METHODS: Eighty-six women had this diagnosis (EH) confirmed pre-pregnancy by 24-hour ambulatory blood pressure monitoring (ABPM) or repeated automated home blood pressure (BP) self-measurement. The remaining 155 underwent 24-hour ABPM in early pregnancy to establish their diagnosis. Women found to have WCH did not receive antihypertensives during their pregnancy, whereas those with confirmed EH received oxprenolol or methyldopa. Women with WCH had repeated 24-hour ABPM and/or BP assessments in a pregnancy day assessment unit until delivery. MAIN OUTCOME MEASURE: The development of PE in women with WCH or EH. RESULTS: The overall prevalence of WCH was 32%. Half retained this phenomenon throughout pregnancy and had good pregnancy outcomes. Forty percent developed (benign) gestational hypertension and also had good pregnancy outcomes while 8% developed proteinuric PE, significantly fewer than in women with confirmed EH (22%), P= 0.008. No BP parameter at study entry permitted discrimination between those women with WCH who retained this phenomenon and those who developed GH or PE. CONCLUSION: WCH is a common phenomenon in pregnant women who appear to have EH according to routine BP measurement early in pregnancy. Antihypertensives may be withheld from this group initially and they can be advised they will have better pregnancy outcomes than women with true EH. However, continued monitoring throughout pregnancy remains important to detect the small group of white coat hypertensives who develop PE.