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Routine Blood Pressure Measurement In Pregnancy

The aim of these guidelines is to assist midwives and doctors in accurate measurement of blood pressure to identify the likely onset of hypertensive disorders of pregnancy.

Evidence

Pre-eclampsia is a major cause of maternal and perinatal morbidity and mortality. Elevated blood pressure is one of the first signs of the condition. Consequently, guidelines recommend the practice of recording blood pressure at every antenatal visit as critical to detection and management of hypertensive disorders of pregnancy. Early detection is important, as underlying conditions can progress rapidly (1-3).

Current Australasian consensus guidelines suggest a diagnosis of hypertension when systolic blood pressure is 140 mmHg and diastolic blood pressure is 90 mmHg taken on two or more consecutive occasions over several hours, or an increment of 15/30. Both diastolic and systolic pressures have been shown to be closely associated with fetal outcome. A clinical diagnosis of pre-eclampsia is usually made when hypertension occurs with one or more of proteinuria, renal insufficiency, liver disease, neurological problems, haematological disturbances or fetal growth restriction (1).

Accurate measurement of blood pressure is impeded by lack of standardisation in:

  • Patient position
  • Use of Korotkoff sound for diastolic blood pressure
  • Cuff size
  • Rounding of measurement
  • Selection of left or right arm
  • Period of pre-measurement resting (2-5)

Methods of Search and Appraisal

Two main strategies were used to search and appraise evidence relating to blood pressure measurements in pregnancy.

I. General Literature Search (February 2000)

The Centre for Clinical Effectiveness conducted a general search of the Medline and CINAHL for articles relating to blood pressure measurement.

II. Search on Defined Questions (November 2000)

A research team from the Department of Perinatal Medicine at the Royal Women's Hospital searched The

Cochrane Library (2000). The OVID interface was used to search Medline 1980 - 2000, CINAHL April 1982 - 2000, and Best Evidence 2000 to answer:

  1. In low risk pregnant women, does blood pressure measured by the same person at every visit detect hypertension and pre-eclampsia more accurately than measurements taken by more than one person?
  2. In low risk pregnant women does blood pressure measurement taken in the semi-recumbent position (seated) detect hypertension and pre- eclampsia more accurately than measurements taken in other positions?

Search terms included blood pressure, blood pressure and pregnancy, pre-eclampsia and hypertension and pregnancy.

Bibliographies were also hand searched. Articles were excluded if they were not in English, or related to postnatal diagnosis, ultrasonography, biochemical diagnosis, treatment and/or management issues. Twenty-four citations were identified and included as relevant to the search questions. There was no Level I literature identified. However, there was one Level II, five Level III-2, eight Level III-3 and ten Level IV studies/documents. The review included a recent consensus statement by the Australian Society for the Study of Hypertension in Pregnancy. The coordinator searched grey literature and journals for additional evidence published between December 2000 and August 2001.

References

  1. US Preventive Services Task Force. Guide to Clinical Preventive Services. 2nd Ed. Baltimore: Williams and Wilkins, 1996. Level IV
  2. Canadian Task Force on the Periodic Health Examination. The Canadian Guide to Clinical Preventive Health Care. Ottawa: Canada Publishing Group, 1994. Level IV
  3. Australian Society for the Study of Hypertension In Pregnancy. The detection, investigation and management of hypertension in pregnancy: full consensus statement. ANZJOG 2000;40:139-155. Level IV
  4. McAlistair F and Strauss SE. Measurement of blood pressure: an evidence based review. BMJ 2001;322:908-911. Level IV
  5. Brown MA, Buddle M, Farrell T, Davies G, Jones M. Randomised trial of management of hypertensive pregnancies by Korotkoff phase IV or phase V. Lancet 1998;352:777-781. Level II

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