Prognostic value of 24-hour blood pressure in pregnancy.

CONTEXT Elevated blood pressure (BP) measured at the physician's office may reflect true hypertension or white coat hypertension (WCH). The prognostic value of WCH among pregnant women is unknown. OBJECTIVE To assess the prognostic value of WCH in pregnancy. DESIGN Prospective cohort study conducted between September 1994 and October 1997. SETTING Community hospital. PATIENTS Women without preexisting hypertension and not treated with antihypertensive drugs aid with high (n = 148) or normal (n = 106) office BP (high office BP was defined as > or =140 mm Hg systolic and/or > or =90 mm Hg diastolic) matched for gestational age during their third trimester of pregnancy. All women underwent 24-hour noninvasive BP monitoring, and women without hypertension on 24-hour monitoring (125/74 mm Hg or less for average 24-hour BP) with office hypertension were classified as having WCH. Women were followed up through the end of pregnancy. MAIN OUTCOME MEASURES Duration of pregnancy, gestational hypertension, preeclampsia or eclampsia, cesarean delivery, placental and neonatal weight, and length of maternal and neonatal hospital stays for those with and without elevated office BP. RESULTS After application of exclusion criteria, data for 7 women were removed from the analysis. For the remaining subjects, in the group with elevated BP, prevalence of WCH was 29.2% (42/144). Duration of pregnancy was similar in the normotensive and WCH groups (39.6 vs 39.8 weeks; P = .50), but shorter (38.3 weeks; P<.001) in the true hypertension group. Incidence of preeclampsia was similar in the normotensive and WCH groups (5.8% vs 7.1 %; P = .86) but higher in the true hypertension group (61.7%; P<.001). Frequency of cesarean delivery was lower in the normotensive (12.4%) than in the WCH (45.2%; P = .008) and true hypertension (41.1 %; P = .009) groups. Neonatal weight was lower (P<.001) in the true hypertension (mean, 2911 g) than in the normotensive (3336 g) and WCH groups (3435 g), which did not differ (P = .68). The duration of neonatal hospital stay did not differ between the normotensive and the WCH group (5.3 vs 6.9 days; P = .13) but was longer in the true hypertension group (12.3 days; P<.001). CONCLUSIONS In women with elevated BP during their third trimester of pregnancy, 24-hour BP was superior to office BP (distinguishing true hypertension from WCH) for prediction of the outcome of pregnancy. Outcomes in the normotensive and WCH group were comparable, but the increased incidence of cesarean delivery in the WCH group may reflect decision-making processes influenced by office BP.