What is the clinical evidence from this study?

Study design: Cross-Sectional. Population: Pregnancy (n=4023). Intervention: Automated blood pressure measurement. Primary outcome: Blood pressure.

March 4, 2004

Cross sectional study of automated blood pressure measurements throughout pregnancy

Key Result

Automated blood pressure measurements in 4023 pregnant women established that values >130/80 mmHg and <90/50 mmHg represent the 95th and 5th centiles, respectively.

Study Design

Type

Cross-Sectional (n=4,023)

Multicenter

Structured PICO

What are the reference ranges for automated blood pressure measurements throughout pregnancy in a large population?

Population

4023 pregnant women with accurately dateable singleton pregnancies (Caucasian: n=3234; Asian: n=577; Black: n=212) not receiving antihypertensive medication

Intervention

Automated blood pressure measurement using an oscillometric device (Dinamap)

Outcome

Blood pressuresurrogate

The study establishes new reference ranges for automated blood pressure in pregnancy, suggesting that the WHO definition of high diastolic BP (>90 mmHg) may be too conservative for detecting pre-eclampsia risk.

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= 3234; Asian predominantly from Sri Lanka, Thailand and the Philippines: n= 577; Black n= 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 or=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 >or=95th centile (>or=130/80 mmHg) and <or=5th centile (<or=90/50 mmHg).

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