The prevalence and clinical significance of nocturnal hypertension in pregnancy

Objective To determine (a) the prevalence of hypertension during sleep in pre-eclampsia and gestational hypertension, and (b) whether women with hypertension during sleep have worse pregnancy outcomes than hypertensive pregnant women with controlled (normal) blood pressure (BP) during sleep. Design Prospective double-blind cohort study. Setting Inpatients and outpatients managed in a day assessment unit (DAU) at St George Hospital, Sydney, Australia. Participants A total of 186 hypertensive pregnant women, 158 of whom had successful 24 h BP monitoring; 40% had proteinuric pre-eclampsia (PE), 43% gestational hypertension (GH) and 17% essential hypertension (EH). Interventions Blood pressure, 24 h non-invasive, monitoring (Spacelabs 90207) was undertaken successfully in 158 women with PE, GH or EH, whether or not they were receiving antihypertensives. Women and clinicians were blinded to results of these BP monitors. Sleep hypertension was defined as BP > 117/68 mmHg at 26-30 weeks or > 123/72 mmHg after 30 weeks gestation. Main outcome measures Maternal and fetal outcomes were compared between women with and without sleep hypertension and the prevalence of sleep hypertension was determined. Results Sleep hypertension was present in 59%, more commonly in PE (79%) than GH/EH (45%), P < 0.0001. Sleep hypertensives also had higher routine sphygmomanometer Bps [137(10)/91(7) mmHg; mean(SD)] than women with normal sleep BP [130(12)/87(8) mmHg] P = 0.007, and higher awake ambulatory blood pressure monitoring (ABPM) Bps [137(8)/88(7) versus 127(7)/79(6) mmHg], P < 0.0001. Awake, but not sleep, average heart rate was lower in sleep hypertensives [85(11) versus 91(10) beats per minute, bpm], P = 0.002. Sleep hypertensives had a significantly greater frequency of renal insufficiency, liver dysfunction, thrombocytopenia and episodes of (awake) severe hypertension (P < 0.05), as well as lower birth weight babies [2715(808) versus 3224(598) g, P < 0.0001]. Conclusions Hypertension during sleep is a common finding in women with hypertensive disorders of pregnancy, particularly pre-eclampsia. These women also have higher awake BPs and a greater frequency of adverse maternal and fetal outcomes. These findings are largely explained by the greater likelihood of pre-eclamptics having sleep hypertension.