Home blood pressure monitoring, risk factors and complications of hypertensive disorders in pregnant women

Abstract

Preeclampsia (PE) and gestational hypertension (GH) are disorders of pregnancy defined by hypertension. Blood pressure (BP) measurement by mercury sphygmomanometer is routinely used in their detection and management, but ambulatory blood pressure monitoring (ABPM) and self-initiated BP monitors may have a clinical role in the future. A community based, nested case control study cohort of healthy, nulliparous women (n=1496) was investigated to determine maternal and fetal complications and risk factors in women with PE (n=71), GH (n=117) and randomly selected controls (n=223). Severe maternal disease developed in 63.4% of women with PE and 26.50% with GH. The rate of caesarean section (42.2% PE, 30.8% GH, 22.9% controls), preterm delivery (35.2% PE, 6.0% GH, 3.6% controls), and small for gestational age (SGA) infants (25.4% PE,20.5% GH, 11.7% controls) was increased in the cases. Early (<37 weeks; n=7) and late onset (n=110) GH and very early (≤ 32 weeks; n=11), early (33-36 weeks; n=14) and late onset (n=46) PE disease were investigated to determine maternal and fetal complications. A woman with early onset GH was 12 times more likely to have a SGA infant [O.R. 12.0 (95%C.I. 1.84-97.5) p=0.004] and 86% delivered early due to fetal compromise. All women with very early onset PE developed severe maternal disease and delivered by caesarean section if the infant was viable. Multisystem disease was evident in 82% and 64% had a SGA infant. Age, smoking, previous pregnancy, booking BP and weight were investigated for prediction of preeclampsia. A healthy, nulliparous woman with a < 20 week nadir systolic BP ≥120 mmHg and a booking weight of ≥80kg went from having a 1 in 21 to a 1 in 7 chance of developing PE. Conversely a woman with a <20 week nadir systolic BP ≤100 mmHg and a booking weight of ≤60kg had a 1 in 48 chance of developing PE. A longitudinal reference range was established in a group of healthy, pregnant women (n=102) for ABPM using the SpaceLabs 90207 monitor and for the Omron HEM 705CP home self-initiated monitor. Differences with mean mercury office measurements were compared for both office and home mean monitor measurements. The mean systolic and diastolic BP differences for both home Omron and 24 hour ABPM were small (-1 to 2 mmHg), but individual women showed large scatter about the mean with standard deviations of 6-8 mmHg, which would be of concern if the monitors were to be used in the clinical setting. The clinical significance of BP measurements with these monitors needs to be established. Night-time during 24 hour ABPM was defined by sleep diary entries. Comparisons were made between actual sleep periods and arbitrary periods of time to define night-time. Values were similar for group data but individual women who napped during the day (20% during pregnancy) had significantly lower BP values compared to those who remained awake (P <0.0001). During pregnancy, night-time ABPM should be defined by periods of sleep. Non-dipping status (<10% drop in night-time MAP), which has been associated with development of PE, was investigated in the reference range study. Non-dipping was common, with 1 in 3 women failing to have a fall in night-time MAP at least once during pregnancy. There was no consistency in non-dipping following the first episode and in our small cohort it was not associated with subsequent PE or GH. Any monitor, to be useful, needs to be acceptable to pregnant women. An investigation of the acceptability of the SpaceLabs 90207 ABP and the home self-initiated Omron HEM 705CP monitor was made with women in the reference range study as well as a group of hospitalised hypertensive women (n=47). The Omron monitor was more acceptable. The Spacelabs monitor caused discomfort and interfered with sleep. In conclusion, data is presented on the rate of maternal and fetal complications in healthy, nulliparous women who develop PE and GH. A longitudinal reference range for ABPM and Omron home monitoring is given for pregnant women and the rate of non-dipping is reported. Evaluations of the acceptability of the monitors are presented.