CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 6, November/December 2011
332
AFRICA
tion blood pressure (
>
30/15 mmHg) should lead to closer moni-
toring, but it is not diagnostic of hypertension in pregnancy.
12
Chronic hypertension
Chronic hypertension presents prior to pregnancy or before the
twentieth week of gestation. It is reported to complicate 3% of
all pregnancies and is more common in women who are obese
or those over the age of 35 years. It is important to note that
20–30% of women with chronic hypertension go on to develop
superimposed pre-eclampsia.
13
Pre-eclampsia/eclampsia syndrome
Pre-eclampsia is a syndrome of new-onset hypertension
(
>
140/90 mmHg) occurring after the twentieth week of gesta-
tion, with proteinuria (2
+
on dipstick on two occasions six hours
apart or
>
3 g/24-hour urine collection).
12
The aetiology remains elusive but current views suggest
that it is a two-stage disorder.
14
Put simply, the first stage is
one of placental hypoperfusion, resulting in the release of a
variety of substances (apoptotic cells, trophoblastic debris and
anti-angiogenic factors) which cause multisystemic endothelial
damage. The second stage presents as the clinical syndrome of
hypertension, proteinuria, hepatic and central nervous system
dysfunction.
14
It is difficult to predict which organ system will be
predominantly affected, but in general terms, the clinical signs of
hypertension and proteinuria are the commonest. Pre-eclampsia
therefore represents a spectrum of endothelial damage leading to
downstream health effects.
Pre-eclampsia is divided into mild and severe categories.
Severe disease is characterised by hypertension, namely, blood
pressure values above 160/100 mmHg, proteinuria above 5 g
per 24 hours, neurological symptoms (headache, visual distur-
bances), renal compromise (elevated serum creatinine and urea),
hepatic dysfunction and haemolysis, and intra-uterine growth
restriction. The presence of these symptoms and signs constitutes
a medical/obstetric emergency, requiring admission to hospital
and a multi-disciplinary approach to management.
12
Although the exact aetiological mechanism is not known,
epidemiological evidence suggests that pre-eclampsia affects the
future health of the woman and her baby. Women with a history
of pre-eclampsia are twice as likely to develop hypertension and
two to five times more likely to have an ischaemic stroke in later
life.
4,5
It is unlikely that placental dysfunction on its own (stage I)
leads to the pre-eclamptic disorder, but interactions with mater-
nal constitutional factors (genetic, behavioural or environmental)
may also be involved in the second stage of the disease process.
The ultimate therapy for pre-eclampsia is delivery of the
baby, because the exact cause of the disease is not known.
Clinical management is therefore individualised. In women
with early-onset superimposed pre-eclampsia, blood pressure
levels may increase quickly, be labile and require therapy as
for a hypertensive emergency.
15,16
In such circumstances, rapid
lowering of high blood pressure and delivery of the baby, even if
premature, may be required to prevent maternal complications.
17
Treatment of high blood pressure alone will not prevent obstetric
complications in such settings, and delivery of the foetus may
be necessary to prevent adverse events in pregnancy, labour and
the puerperium.
There is no doubt in the literature that women with sustained
blood pressure values above 160 mmHg systolic and/or 110
mmHg diastolic should be treated with antihypertensive
agents.
16-18
On the other hand, there is little evidence to support
antihypertensive therapy in pregnant women with blood pressure
values below 160/100 mmHg. Nevertheless, in the clinical situ-
ation, there is a tendency to use antihypertensive medications in
such circumstances, together with lifestyle modifications (diet
and exercise).
Lifestyle modifications should ideally be initiated prior to
conception in women with chronic hypertension, and continued
in pregnancy. Exercise has been associated with reductions in
gestational hypertension and a lower risk of eclampsia/pre-
eclampsia. Due consideration however, needs to be given when
making recommendations to maintain calorie intake and prevent-
ing injury.
8-10
Antihypertensive drugs in pregnancy
Table 1 lists the commonly used antihypertensive drugs. First-line
agents include methyldopa, nifedipine and labetalol. Methyldopa
is the most commonly used antihypertensive medication and the
most studied. It has a long history of safety, is well tolerated
and efficacious, and is often the first medication attempted in
pregnant women. Methyldopa can be used three times daily,
particularly if high doses are required. This dose makes it a cost-
effective method of treatment. Labetalol has also been studied
extensively and found to be effective, although some studies have
associated it with foetal growth restriction.
Angiotensin converting enzymes/angiotensin receptor block-
ers should be avoided in pregnancy and in women intending to
become pregnant. These agents are associated with renal agen-
esis and foetal death.
19
If a woman becomes pregnant while on
angiotensin converting enzymes/angiotensin receptor blockers,
these agents should be stopped immediately and alternate agents
that have been found to be safe in pregnancy should be used. It
is also important to note that if these agents are to be considered
for use in young women of childbearing age, careful counselling
and contraceptive advice must be offered.
13,20
There are theoretical concerns regarding the use of diuretics
during pregnancy. These include decreased placental perfusion
and neonatal thrombocytopenia; therefore diuretics are not first-
line agents. Calcium channel blockers are used in pregnancy.
Most of the literature is on the use of nifedipine and it is regarded
as safe for use in pregnancy.
18,21
Other calcium channel blockers
are probably safe although the manufacturers do not recommend
their use. Selective
b
-blockers are considered safe during preg-
nancy but high doses are associated with neonatal hypoglycae-
mia and low birth-weight babies.
18
Antihypertensive medication needs to be continued after
delivery because blood pressure remains elevated for at least
three to five days following delivery.
18,19
Observational studies
suggest that up to 25% of women with severe pre-eclampsia have
ongoing postnatal hypertension.
22
Consequently, a step-down
approach to reducing the use of antihypertensive agents should
be taken rather than stopping abruptly. Most antihypertensive
agents are expressed in breast milk in minimal quantities.
Hypertension in young women: pregnancy
and the general practitioner
In South Africa, the general practitioner is often faced with
