Approach
Diagnosis of gestational hypertension is based on at least two elevated blood pressure (BP) readings (≥140/90 mmHg) in the absence of proteinuria occurring after 20 weeks' gestation. All manifestations of gestational hypertension are presumptive until retrospectively confirmed by complete resolution of hypertension and any other new abnormalities in the postpartum period.
Clinical evaluation
Pre-pregnancy BP readings help to establish whether the BP elevation is a new problem. If the woman's previous BP status is unknown, the initial reading is regarded as the baseline; therefore, distinguishing gestational hypertension from chronic hypertension may only be possible after the pregnancy.
Women with gestational hypertension are usually asymptomatic. The woman should be asked about symptoms that suggest pre-eclampsia, such as weight gain, oedema, headaches, and upper abdominal pain.
A detailed personal and family history should be elicited, with evidence of cardiovascular disease or its risk factors (e.g., diabetes mellitus, dyslipidaemia) documented.
Investigations
Twenty-four hour BP monitoring can be considered when BP readings are equivocal.[2] However, more evidence is needed on whether ambulatory BP monitoring is beneficial in women with gestational hypertension.[27] One small randomised controlled trial found no difference in outcomes between the use of a manual BP device (sphygmomanometer) and an automated BP device in pregnant women with hypertension (essential, gestational, or pre-eclampsia).[28]
Urinalysis should be performed at antenatal visits and results interpreted in the context of a clinical review for pre-eclampsia. A quantitative urinary protein collection is required if urinalysis is positive or if a suspicion of pre-eclampsia is present from the clinical evaluation. Twenty-four hour urine collection is awkward for women and, where available, alternative spot tests such as protein:creatinine ratio (PCR, for which a result of ≥30 mg/mmol is diagnostic) and albumin:creatinine ratio (ACR, for which a result of ≥8 mg/mmol is diagnostic) are preferred.[1][6]
Pregnant women with a new diagnosis of hypertension should have baseline blood tests (full blood count, liver function tests, electrolytes, urea, and creatinine, uric acid) to screen for pre-eclampsia, with care taken to use pregnancy-specific thresholds.
On diagnosis of gestational hypertension, ultrasound examination of estimated fetal weight and amniotic fluid index and umbilical artery doppler velocimetry are recommended.
If pre-eclampsia is suspected:
A range of additional maternal and fetal investigations may be recommended, including fetal cardiotocography, full blood count, renal function, and liver function tests. Where available, the use of placental growth factor (PIGF)-based testing may reduce the time to diagnosis of pre-eclampsia, with consequent reduction in incidence of severe maternal adverse outcomes in women presenting between 20-36 weeks plus 6 days of gestation.[6][29][30] See Pre-eclampsia (Diagnostic approach).
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