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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 30, No 2, March/April 2019
120
AFRICA
Blood pressure measurement in pregnancy and
in hypertensive disorders of pregnancy: devices,
techniques and challenges
Nnabuike C Ngene, Jagidesa Moodley
Abstract
Measurement of blood pressure is essential for clinical
management of patients. To obtain an accurate blood pres-
sure reading, the use of a validated device and an appropri-
ate technique are required. This is of particular importance
in pregnancy where the physiological changes affect vessel
wall compliance. Moreover, currently it is difficult to predict
in early pregnancy (prior to 20 weeks of gestation) which
women would develop hypertension or pre-eclampsia. For
this reason, blood pressure devices require validation in preg-
nancy and in hypertensive disorders of pregnancy to ensure
that accurate readings are obtained and utilised for clinical
decisions, otherwise the safety of the mother or the foetus/
neonate or both may be compromised. The authors provide
a narrative review on devices and techniques for blood pres-
sure measurement in pregnancy and hypertensive disorders of
pregnancy as well as the associated challenges.
Keywords:
blood pressure devices, importance of blood pressure
measurement, myocardial performance, pre-eclampsia, rate pres-
sure product, vascular changes in pregnancy
Submitted 4/8/17, accepted 31/10/18
Published online 23/1/19
Cardiovasc J Afr
2019;
30
: 120–129
www.cvja.co.zaDOI: 10.5830/CVJA-2018-067
Each year, over 70 000 maternal deaths and over 500 000 foetal
and neonatal deaths occur as a result of pre-eclampsia (PE).
1
In 2015, a global maternal mortality ratio of 216 deaths per
100 000 live births was reported,
2
and hypertensive disorders
of pregnancy (HDP), mainly the category PE, accounted for
14% of these deaths with most of the mortalities occurring in
low- and middle-income countries (LMIC).
3
In the 2014–2016
triennium in South Africa, HDP accounted for an in-hospital
maternal mortality ratio of 24.01 per 100 000 live births.
4
Sixty-six per cent of these maternal deaths were associated
with an avoidable factor, including failure by some healthcare
practitioners to manage severe hypertension as an emergency.
4
Maternal deaths due to HDP in other countries are also
associated with suboptimal management in different aspects of
patient care, such as antihypertensive therapy, stabilisation prior
to delivery, timing of delivery and quality of care.
5
One of the ways to reduce the morbidity and mortality rate
from HDP is to ensure accurate measurement of blood pressure.
To a large extent, the steps involved in the measurement of blood
pressure in pregnancy are the same as in the non-pregnant state.
6
Unfortunately, a number of reports indicate that healthcare
practitioners do not always use the recommended techniques to
measure blood pressure.
7-10
Additionally, due to the concern of
mercury toxicity, automated blood pressure-measuring devices
have been introduced to replace mercury sphygmomanometers.
However, automated blood pressure devices are prone to errors in
pregnancy and especially in HDP due to haemodynamic changes
that alter vascular wall compliance.
11,12
To ensure accuracy,
automated blood pressure devices used for the measurement of
blood pressure in pregnancy have to pass a validation protocol
13-17
or a baseline check recommendation.
18
The immediate and long-term complications of poorly
managed HDP make this topic important. These complications
include posterior reversible leukoencephalopathy syndrome,
19
stroke,
20-22
retinal disorders,
23
cerebral white matter lesions
24
and
increased risk of mortality in early adulthood,
25,26
to mention
but a few. Additionally, the category of HDP called PE is a risk
factor for the development of cardiovascular and metabolic
disorders at a later stage in life.
27-29
Furthermore, offspring of
pre-eclamptic mothers are at risk of major health issues such
as impaired motor development,
30
increased childhood blood
pressure
31
and stroke in adulthood.
21
The aim of this narrative review, therefore, is to elaborate on
devices and techniques for the measurement of blood pressure
in pregnancy and HDP, and in particular PE. This review also
discusses and offers solutions to the challenges associated with
conventional blood pressure measurement in pregnancy. The
index report will be valuable to healthcare professionals and
researchers who provide medical care to pregnant women.
Classification of hypertensive disorders of
pregnancy
Hypertension in pregnancy is defined as systolic blood pressure
≥
140 mmHg and or diastolic blood pressure
≥
90 mmHg,
and these levels must be attained or exceeded during a repeat
measurement.
1
Notably, the blood pressure threshold that is
used to define hypertension is dependent on the situation of
measurement: clinic
≥
140/90 mmHg; home
≥
135/85 mmHg;
ambulatory blood pressure prior to 22 weeks’ gestational age
≥
126/76 mmHg (24-hour average),
≥
132/79 mmHg (awake
average) and
≥
114/66 mmHg (sleep average).
1
Department of Obstetrics and Gynaecology, University of
KwaZulu-Natal, Durban, South Africa
Nnabuike C Ngene, Dip HIV Man (SA), MMed (FamMed), FCOG,
MMed (O&G),
ngenenc@gmail.comJagidesa Moodley, MB ChB, FRCOG, FCOG, MD