34 24-Hour ambulatory blood pressure monitoring in women with chronic hypertension and the development of placental disease requiring preterm delivery

Abstract

Introduction Iatrogenic preterm delivery as a result of pre-eclampsia (PE) and/or fetal growth restriction (FGR) is common (23%) in women with hypertensive disease in early pregnancy. We sought to determine whether ambulatory blood pressure (ABPM) profiles recorded in early pregnancy were different in women who subsequently developed pregnancy complications. Objectives Compare ABPM profiles from a high-risk cohort and determine differences between those with and without an iatrogenic preterm delivery. Methods An exploratory study was performed including 55 women. Women attending the Manchester Antenatal Vascular Services (MAViS) clinic who were 20 weeks gestation were offered ABPM. They were fitted with a SpaceLabs 90217A and asked to record sleep, wake and drug ingestion times. The BP was recorded every 30 min between 08:00 and 22:00 and hourly between 22:00 and 08:00. Results The median gestation was 113 (IQR: 101–125) days. 39 women had chronic hypertension, 10 had renal hypertension, 4 had previous pre-eclampsia and 2 had suspected white coat hypertension. 35 (64%) women were taking antihypertensive medication during the period of monitoring; Labetalol n = 12, Nifedipine n = 15, Amlodipine n = 2, Methyldopa n = 1 and poly-pharmacy n = 5. 18 (33%) women required an iatrogenic preterm delivery, 17 (31%) developed PE (1 NND), 11 (20%) had FGR. The average daytime systolic and diastolic BP readings were not significantly different between groups: 133.7 mmHg (95% CI 130–137) vs 131.9 (125–138) and 85.2 mmHg (82.2–88.1) vs 83.8 (79.6–87.9), respectively. Similarly there was no difference in night time readings or in the night time dip; systolic 10.6 mmHg (8.6–12.7) vs 10.5 (8.2–12.8) and diastolic 14.0 (11.2–16.8) vs 13.6 (10.5–16.7). There was a non-significant trend towards an effect of ethnicity (black (n = 19) vs non-black (n = 35)) on night time BP profiles (p = 0.1) and black women were more likely to develop complications requiring iatrogenic preterm delivery (58% vs 29%; p = 0.057). In logistic regression models neither day or night time blood pressure characteristics, adjusted for medication type or ethnicity, were associated with the need for iatrogenic preterm delivery (p > 0.05). Conclusion In this small preliminary study of high-risk women undergoing ABPM in early pregnancy, blood pressure characteristics were not predictive of adverse outcomes. ABPM profiles were unavoidably modified using medication in this study and therefore pathophysiological associations between BP and pregnancy outcome may have been attenuated; further study is necessary to determine the effect of early pregnancy haemodynamics on placental function and development.