A Prospective Randomized Study of Automated versus Mercury Blood Pressure Recordings in Hypertensive Pregnancy (PRAM Study)

Abstract

Background. Mercury sphygmomanometry is being replaced with automated blood pressure (BP) recording. We tested the potential impact of this change on the outcomes of pregnant women with hypertension. Methods. Following routine detection of hypertension by mercury sphygmomanometry, 220 pregnant women with hypertension were randomized to have all subsequent BPs recorded with either mercury sphygmomanometry or an automated BP device (Omron HEM-705CP) for the remainder of their pregnancy. We used a prospective randomized open study with blinded end points design. Main Outcome Measures. The primary maternal outcome measure was the number of women having any episode of severe hypertension (BP 170/110 mmHg). The primary fetal outcome measure was small for gestational age baby. Results. Both groups were similar in age, weight, parity, race, use of assisted reproductive technology before this pregnancy, diabetes prevalence, smoking, mercury BP in the first trimester, use of antihypertensives at the time of study entry, and type of hypertension (essential, gestational or preeclampsia) at study entry. Severe hypertension occurred in 39% of women using mercury sphygmomanometry and 44% using the automated device (p = 0.5). Small for gestational age rates were 12 and 17%, respectively (p = 0.3). About 47% of women had preeclampsia at delivery. Birth weight and perinatal mortality were similar between groups. Conclusions. Using this automated BP recording device in hypertensive pregnant women is associated with similar maternal and fetal outcomes as in women whose BP is measured by sphygmomanometry, despite intra-individual BP differences between the two methods of recording BP.

Keywords:

• Automated blood pressure
• Hypertension
• Mercury sphygmomanometry
• Preeclampsia
• Pregnancy

ACKNOWLEDGMENTS

The authors thank Dr. Mike Jones, statistician, for his advice with power calculations. They also thank the midwives who supported the conduct of this study with enthusiasm.

Declaration of Interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this paper