Main findings
This is the first systematic review to our knowledge that investigates
the efficacy of CCBs as treatment for Black women with diagnoses of HDP.
The striking finding from this review is that there is a paucity of
randomised control trials focussed on HDP that publish race or ethnicity
of their study participants, Fewer still report outcomes in relation to
race or ethnicity, representing a significant gap in evidence in these
trials. This is despite the extensive documentation of racial and ethnic
differences in cardiovascular health outcomes out with, during and
following pregnancy.17-19It is therefore impossible to
definitively conclude which anti-hypertensive is most effective for each
pregnant ethnic group.
Outside of the context of pregnancy, national guidelines in the U.K. and
U.S.A. recommend ethnicity based stratification of first‐line
anti-hypertensive agents, with Black patients receiving CCB rather than
Angiotensin‐Converting Enzyme inhibitors (ACE-i) as first line
management of hypertension, regardless of age.6,20These guidelines are based on data from large randomised control trials,
which indicate that CCB are more effective in reducing the risk
cardiovascular disease and stroke in Black
patients.21-23
Another study by Weir et al found that Black patients required between
two and four times the dose of Trandolapril (ACE-i) to obtain a response
similar to that observed in White patients.24 A
systematic review of hypertension treatment for non-pregnant Black
patients concluded that thiazide-like diuretic and CCB monotherapy were
better at achieving target blood pressure levels compared with
beta-adrenergic blocker, ACE-i or angiotensin receptor blocker (ARB)
monotherapy.25These studies demonstrate that it is
possible that Black patients may have different responses to certain
hypertensive drugs compared to other ethnicities. Black patients are at
increased risk of hypertension associated end-organ damage at lower
blood pressure levels compared to other ethnicities, and it is therefore
essential that anti-hypertensives achieve tight control of blood
pressure in this group.26
Previous population studies have demonstrated that chronic hypertension
is more prevalent in younger Black women than Black men or women of
White ethnicity until 75 years of age.27In particular,
Black women are at higher risk for developing refractory hypertension
and often require multiple anti-hypertensive drugs for adequate blood
pressure control.28-29
Women with HDP are more likely to develop essential hypertension and
have an elevated risk of future cardiovascular
disease.30-31In fact, it has been shown that the onset
of cardiovascular dysfunction can be noted as early as shortly after the
index pregnancy affected by HDP.32Black women are
known to be particularly at risk of developing
HDP.33In one study, women of Black ethnicity with HDP
were significantly more likely to require post-partum care in a high
dependency unit compared with White women, suggesting a correlation
between Black ethnic background and increased disease
severity.34 Disparities in socioeconomic status have
been theorised as a plausible explanation for these
differences35 but these do not account entirely for
the variances, given that studies based in free at point-of-care
healthcare systems have previously adjusted for deprivation score as a
baseline characteristic, and still noted that Black women had
significantly worse perinatal outcomes.36-37In another
study, Black women were more likely to have had pre-eclampsia in a
previous pregnancy compared to other ethnicities regardless of BMI
(p=0.014).38They also reported that on any postpartum
day, a Black woman with BMI < 35 was 50 percent less likely to
achieve resolution of HDP than a non-Black woman in the same BMI
category (HR 0.51, 95% CI 0.27–0.95).38The
probability of a Black woman with a BMI ≥ 35 achieving blood pressure
resolution was 71 percent lower (HR 0.29, 95% CI
0.12–0.74).38This data highlights the potential role
of increased severity of maternal disease in Black women with HDP,
independent of other risk factors, further strengthening the argument
that optimisation of anti-hypertensive treatment in this cohort is
crucial in order to ameliorate these clinical discrepancies.
HDP contribute to 2·8 percent, 7·4 percent, and 14 percent of pregnancy
related deaths in the U.K., U.S.A. and worldwide
respectively.39-41Previous reviews have shown that
deaths from HDP are largely preventable, and associated with substandard
care.42 The lack of consensus around whether race
based differences in first line management of hypertension outside of
pregnancy should extend to HDP due to lack of good quality research
represents a lack of evidence-based gold standard care, which may
contribute to the persistent racial disparities in maternal mortality
and morbidity.
This current review highlighted just one randomised control trial, which
stratified HDP outcomes by ethnicity. Webster et al commented on some
treatment effect by ethnicity in their trial comparing Labetalol with
Nifedipine. They reported that Labetalol had a greater effect in
reducing mean diastolic blood pressure in non-Black participants.
Another article included in this review, which could not be used for
meta-analysis due to unavailability of race based outcomes, by Scardo et
al is also of interest as 62 percent of its study population was Black,
the trial with the highest proportion of Black participants. They
demonstrated that Nifedipine was associated with quicker resolution of
raised blood pressure. Additionally, the cohort allocated to Nifedipine
required fewer doses of anti-hypertensive medication to reach target
blood pressure. These two articles in combination support the hypothesis
that CCBs could be more effective in the management of HDP in Black
patients and that Labetalol, which is the current first-line management
of HDP, may not represent the gold standard of treatment in this cohort.
It certainly highlights the need for further research in this area.