Cross sectional study of automated blood pressure measurements throughout pregnancy

Abstract

Objective To generate reliable new reference ranges for pregnancy blood pressure from a large population.Design A prospective cross sectional study.Setting Obstetric outpatient clinic, Zurich University Hospital.Sample Accurately dateable singleton pregnancies (Caucasian: n ¼ 3234; Asian [predominantly from Sri Lanka, Thailand and the Philippines]: n ¼ 577; Black n ¼ 212). Methods Between January 1996 and February 2000 blood pressure was determined in 4023 pregnant women using an oscillometric automated device (Dinamap) according to British Hypertension Society recommendations. Women receiving antihypertensive medication were excluded. Main outcome measure Blood pressure.Results Only the means of duplicate measures at the booking visit (5 -42 weeks) were used in the analysis.Mean blood pressure decreased from early to mid pregnancy before increasing to levels 4 mmHg higher at term than in early pregnancy. Values > 130/80 and <90/50 mmHg were above the 95th and below the 5th centiles, respectively. Parity, age and body mass index were significant determinants in Caucasians. Blood pressure was slightly lower in Asians and Blacks. Conclusions The current World Health Organisation definition of high diastolic blood pressure (!90 mmHg on two occasions) reflects values >2 standard deviations from the mean. This may be too conservative as threshold for detecting women at risk of pre-eclampsia. Further studies are required to determine the prognostic implications of gestational values !95th centile (!130/80 mmHg) and 5th centile ( 90/50 mmHg).

A nationally representative study of maternal obesity in England, UK: trends in incidence and demographic inequalities in 619 323 births, 1989–2007

“…10 This phenomenon was potentially due to the exclusion of late bookers, which theoretically included a large proportion of the target population of obese women in pregnancy. This study adjusted for naturally incurred weight gain of late bookers (women who booked after their first trimester) using published data on BMI change per gestational week 16 rather than excluding late bookers and potentially excluding a large proportion of the obese population.…”

Systolic, Diastolic and Mean Arterial Pressure at 30-33 Weeks in the Prediction of Preeclampsia

“…In normal pregnancy, blood pressure begins to decrease in the first trimester as a result of the fall in systemic vascular resistance due to smooth muscle relaxation and overall vasodilatation caused by elevated progesterone [21,22]. The blood pressure continues to decrease in the second trimester to a nadir by 22-24 weeks' gestation and increases thereafter to prepregnancy levels at term [23]. …”

Changes in blood pressure during healthy pregnancy

“…In some studies, the numerosity of included women is impressive and has enforced their conclusions [1,2,8]. Secondly, the phenomenon can be readily explained physiologically.…”

“…Based on numerous reports describing changes in blood pressure (BP), heart rate (HR), and other hemodynamic variables throughout pregnancy, there has been a general agreement that BP drops in mid-trimester, followed by a progressive increase until term [1][2][3][4][5][6][7][8]. This mid-trimester drop in BP has in part been explained in terms of the development of the low-resistance uteroplacental vascular system [9][10][11] and modification of the renin-angiotensin-aldosterone system [12,13].…”