Oligohydramnios

A multisystem disorder of pregnancy defined by new-onset hypertension after 20 weeks plus evidence of maternal organ dysfunction or uteroplacental dysfunction.

Pathophysiology centers on abnormal placentation, with impaired trophoblast invasion of the spiral arteries leading to placental ischemia and release of anti-angiogenic factors (sFlt-1, soluble endoglin) that drive widespread maternal endothelial dysfunction.

• Severe headache (often frontal, unresponsive to simple analgesia), visual disturbance, epigastric or right upper quadrant pain (hepatic capsule distension), rapidly progressive edema, hyperreflexia with clonus, and reduced fetal movements
• Severe features: BP ≥160/110 mmHg, any of the symptoms above, or HELLP syndrome (Hemolysis, Elevated Liver enzymes, Low Platelets), pulmonary edema, or oliguria

BP ≥140/90 mmHg after 20 weeks plus one or more of:

• Proteinuria (urine protein:creatinine ratio ≥30 mg/mmol, or albumin:creatinine ratio ≥8 mg/mmol, or 24 hour urine protein ≥300 mg)
• Renal insufficiency (creatinine ≥90 micromol/L, or doubling from baseline)
• Liver involvement (transaminases more than twice the upper limit of normal, with or without epigastric/RUQ pain)
• Neurological features (eclampsia, severe headache, visual disturbance, hyperreflexia with clonus, altered mental status)
• Hematological complications (platelets under 150 x10⁹/L, hemolysis, DIC)
• Uteroplacental dysfunction (fetal growth restriction, abnormal umbilical artery Doppler, stillbirth)

Placental growth factor (PlGF) based testing, where available, supports diagnosis and rule-out in suspected cases. Baseline bloods should include FBC, LFTs, U&E, and urate.

• Antihypertensives as per the Gestational Hypertension entry, targeting BP under 135/85 mmHg
• Severe hypertension (≥160/110 mmHg) is an emergency: IV labetalol 20 mg bolus over 2 minutes, doubling every 10 minutes to a maximum cumulative dose of 220 mg, or oral immediate-release nifedipine 10 mg, repeated at 30 to 45 minutes if needed, or IV hydralazine 5 to 10 mg boluses
• Magnesium sulfate for severe pre-eclampsia (not only established eclampsia, as seizure prophylaxis): 4 g IV loading dose over 5 to 10 minutes, then 1 g/hour maintenance infusion, continued for 24 hours after delivery or the last seizure, with monitoring of deep tendon reflexes, respiratory rate, and urine output (see Eclampsia entry for full toxicity monitoring detail)
• Aspirin 75 to 150 mg PO od from 12 weeks in future pregnancies for women meeting high or moderate risk criteria (previous pre-eclampsia, chronic hypertension, CKD, autoimmune disease, diabetes, or 2 or more moderate risk factors)
• Corticosteroids for fetal lung maturation if delivery is anticipated before 34+6 weeks (up to 35+6 in some protocols): betamethasone 12 mg IM, 2 doses 24 hours apart, or an equivalent dexamethasone regimen
• Fluid restriction (typically 80 mL/hour or 1 mL/kg/hour) given capillary leak and pulmonary edema risk
• Delivery is the only definitive treatment; timing is individualized, expectant management if remote from term and stable, with delivery indicated for severe features, deteriorating maternal or fetal status, or reaching 37 weeks even if stable
• HELLP syndrome is managed as severe pre-eclampsia, with correction of coagulopathy and platelet transfusion if under 50 x10⁹/L with active bleeding or before delivery, and expedited delivery

Referral: obstetric emergency requiring senior obstetric and anesthetic involvement; ICU or HDU for severe disease with organ dysfunction.