Critically appraise antihypertensive choice and the management of postpartum and mild hypertension in pregnancy

In one line

Treating non-severe hypertension to a target of <140/90 mmHg now improves outcomes (CHAP); the antihypertensive choice matters less than treating to target, controlling severe levels promptly, and not stopping at delivery — the postpartum window is where most preventable maternal deaths still occur.

This chapter assumes the diagnostic and first-line groundwork in hypertension in pregnancy and pre-eclampsia & HELLP basics; it spends its words on the drug-by-drug argument, the postpartum and mild-disease judgement calls, and the primary-literature appraisal. The expectant-vs-deliver and magnesium-and-fluid craft of severe disease lives in Early-onset severe pre-eclampsia.

Assessment

Assume the Intermediate groundwork — definitions, pre-eclampsia diagnosis and HELLP — from hypertension in pregnancy and pre-eclampsia and HELLP. The decisive question is whether this is hypertension that merely needs a number lowered, or hypertension that signals an evolving multisystem disease.

• Classify before you treat. Chronic hypertension (pre-existing or <20 weeks), gestational hypertension (≥20 weeks, no proteinuria/organ involvement), and pre-eclampsia behave differently and carry different antihypertensive logic. A booking BP is gold — without it, a 20-week reading of 140/95 is uninterpretable.
• Severity is the trigger. Severe hypertension = ≥160/110 mmHg (SA NDoH and international consensus). This is an emergency irrespective of symptoms — the threshold above which maternal intracerebral haemorrhage risk climbs steeply, and the single commonest avoidable cause of direct maternal death.
• Look for the disease behind the number. Headache, visual disturbance, epigastric/RUQ pain, brisk reflexes, oliguria. Bloods: FBC (platelets), U&E/creatinine, ALT/AST, urate, urine protein:creatinine ratio. Rising urate or creatinine, falling platelets or transaminitis reclassify "mild hypertension" as severe disease in a normotensive envelope.
• Postpartum is not the all-clear. BP typically peaks days 3–6 postpartum. De-novo postpartum pre-eclampsia and eclampsia occur, so a woman discharged normotensive on day 1 still needs a plan and a follow-up BP.

The advanced assessment — the subtype distinction that changes the drug

Beyond recognising the clinical picture, the task is to classify the hypertensive subtype well enough to predict its trajectory and pick the right agent, and to recognise the atypical presentations where the "obstetric" label is wrong.

• Chronic hypertension is the highest-risk substrate, not just a baseline number. Pre-existing hypertension carries a roughly threefold increased risk of superimposed pre-eclampsia, and that risk is the reason CHAP-style treat-to-target matters most in this group. Distinguish superimposed pre-eclampsia (new/worsening proteinuria, organ dysfunction, a sudden escalation of BP requirements, rising urate or falling platelets) from chronic hypertension worsening with gestation — the first mandates the full pre-eclampsia pathway (magnesium, delivery planning), the second is a maintenance-dose problem. In a woman who books late with no first-trimester BP, hypertension plus proteinuria after 20 weeks is treated as pre-eclampsia until proven otherwise — you cannot retrospectively "un-diagnose" it.
• "White-coat", masked and gestational-then-resolving phenotypes. White-coat hypertension (raised in clinic, normal on ambulatory/home readings) still carries an elevated pre-eclampsia risk and is not benign; masked hypertension (normal in clinic, raised at home) is the trap that under-treats. Where home/ambulatory BP is available it refines classification, but in most SA district settings the pragmatic answer is serial standardised clinic readings with a correctly sized cuff.
• Severity is a trajectory, not a single reading. A BP creeping from 138/88 to 150/96 over a week in a woman with rising urate is more concerning than an isolated 162/112 in an otherwise stable, asymptomatic chronic hypertensive — the first is an evolving syndrome, the second a number to control. Track the envelope of disease (BP trend + bloods trend + symptoms), not the worst single value.
• The secondary-hypertension mimic that inverts the drug choice. A young woman with paroxysmal severe hypertension, palpitations, sweating, headache and labile pressures that respond badly or paradoxically to a beta-blocker should raise phaeochromocytoma — rare, but lethal if missed and managed as ordinary pre-eclampsia. It changes the drug entirely: alpha-blockade (phenoxybenzamine) must be established before any beta-blockade, because beta-blockade against unopposed alpha stimulation precipitates a hypertensive crisis. Labetalol's fixed oral α:β antagonist ratio (≈1:7) gives inadequate alpha blockade, so labetalol monotherapy in an unrecognised phaeochromocytoma can itself trigger crisis — a clean example of why the right drug depends on the right diagnosis. Other secondary causes (renal artery stenosis, primary aldosteronism, coarctation, intrinsic renal disease) deserve thought in early, severe or treatment-resistant chronic hypertension.

Management

Frame the answer immediate → ongoing → long-term.

Immediate (severe hypertension, ≥160/110). Treat within minutes; do not wait for proteinuria. SA first line is oral nifedipine 10 mg (immediate-release, repeat at 20–30 min to a max of ~3 doses) or IV labetalol where available; IV hydralazine is the third option. Methyldopa has no role acutely — too slow. Severe hypertension and pre-eclampsia also mandate magnesium sulphate for seizure prophylaxis: lowering BP is not the same as preventing eclampsia (MAGPIE).

The named acute regimens — exact doses and how they differ

All three first-line acute agents are acceptable; the right one is the one you can give safely and fast with the access and stock you have. The differences are in titration step, onset, and the failure modes: