Hypertension in Pregnancy

Summary

Hypertensive disorders of pregnancy cause major maternal and fetal complications, including organ failure, placental abruption, growth restriction, and prematurity. They are classified as gestational hypertension, preeclampsia–eclampsia, or chronic hypertension. Diagnosis relies on new-onset blood pressure ≥ 140/90 mm Hg after 20 weeks, with management centered on antihypertensives, magnesium sulfate for severe cases, and delivery as the definitive treatment.

Introduction

Hypertensive disorders of pregnancy (HDP) are a major cause of maternal and perinatal morbidity and mortality worldwide. They predispose mothers to multi-organ complications, including renal and hepatic failure, cerebrovascular events, pulmonary edema, disseminated intravascular coagulation (DIC), and placental abruption. For the fetus, adverse outcomes include intrauterine growth restriction (IUGR), prematurity (often iatrogenic to preserve maternal safety), perinatal death, and complications related to placental insufficiency. These disorders are characteristically progressive, unpredictable, and ultimately curable only by delivery.

Classification

According to the National High Blood Pressure Education Program Working Group (2000) and ACOG (2002), hypertensive disorders in pregnancy are categorized into four groups:

1. Gestational hypertension

• New-onset hypertension (≥ 140/90 mm Hg) after 20 weeks’ gestation or within 72 hours postpartum.

• Absence of proteinuria or end-organ dysfunction.

• Resolves within 12 weeks postpartum; persistence beyond this indicates chronic hypertension.

• Retrospective diagnosis is possible only after delivery if proteinuria does not develop.

2. Preeclampsia–eclampsia syndrome

• Hypertension with proteinuria and/or evidence of end-organ dysfunction.

• Eclampsia is defined by the occurrence of seizures.

3. Chronic hypertension

• Preexisting hypertension before pregnancy, onset before 20 weeks’ gestation, or persistence beyond 12 weeks postpartum.

• May be essential or secondary to renal, vascular, or endocrine disorders.

4. Chronic hypertension with superimposed preeclampsia

• Development of new-onset proteinuria, worsening hypertension, or end-organ involvement in a woman with preexisting hypertension.

Epidemiology

Hypertensive disorders complicate 6–8% of pregnancies and remain a leading cause of maternal morbidity and mortality globally.

Etiology and Risk Factors

The precise pathogenesis remains unclear, but abnormal placentation with defective remodeling of spiral arteries is central, leading to placental hypoperfusion, endothelial dysfunction, and release of vasoactive and prothrombotic factors.

Maternal risk factors include:

• Age < 20 or > 35 years

• Nulliparity

• Obesity (BMI ≥ 30)

• Diabetes mellitus or gestational diabetes

• Chronic hypertension or renal disease

• Systemic lupus erythematosus or thrombophilia (e.g., antiphospholipid syndrome)

• Family history of preeclampsia

• Non-Hispanic Black ethnicity

Pregnancy-related risk factors include:

• Multiple gestation

• Hydatidiform mole

• Fetal anomalies

• Previous history of preeclampsia

Diagnosis

Diagnosis relies on blood pressure ≥ 140/90 mmHg on two occasions ≥ 4 hours apart, after 20 weeks’ gestation, in previously normotensive women. Severe hypertension is defined as ≥ 160/110 mm Hg.

Workup includes:

• Urinalysis or 24-hour urine collection for proteinuria

• Serum creatinine, electrolytes, liver function tests, complete blood count, LDH

• Baseline studies in chronic hypertension to detect superimposed preeclampsia

• Fetal surveillance: ultrasonography (growth, Doppler flow, amniotic fluid), cardiotocography, and biophysical profile

Management

Management depends on gestational age, disease severity, and maternal-fetal status.

• Antihypertensives in pregnancy:

• First-line: Methyldopa, labetalol, nifedipine

• For severe/urgent control: IV labetalol, hydralazine, or oral nifedipine

• Avoid ACE inhibitors and ARBs during pregnancy (fetotoxic).

• Postpartum: Enalapril is safe in breastfeeding women; methyldopa should be discontinued due to risk of postpartum depression.

• Magnesium sulfate is indicated for seizure prophylaxis in severe preeclampsia, eclampsia, and HELLP syndrome.

• Timing of delivery:

• ≥ 37 weeks: delivery is indicated for all types of hypertensive disorders.

• < 37 weeks: individualized management with close monitoring; corticosteroids may be given for fetal lung maturation.

• Immediate delivery is indicated in cases of eclampsia, HELLP syndrome, pulmonary edema, placental abruption, severe refractory hypertension, or non-reassuring fetal status.

Complications

Maternal: placental abruption, DIC, stroke, acute kidney injury, hepatic hematoma/rupture, ARDS, aspiration pneumonia, and increased long-term risk of cardiovascular disease, diabetes, and chronic kidney disease.

Fetal: growth restriction, preterm birth, hypoxia, stillbirth, and perinatal death