Are Diuretics Contraindicated in Pregnancy-Induced Hypertension?
Diuretics are not absolutely contraindicated in PIH, but they are generally not recommended as first-line therapy and should be avoided in pre-eclampsia due to concerns about reducing uteroplacental perfusion. 1, 2
Clinical Context and Rationale
The controversy surrounding diuretics in PIH stems from physiological concerns rather than evidence of direct harm:
- Pre-eclampsia specifically: Diuretics are contraindicated because uteroplacental circulation perfusion is already reduced in pre-eclampsia with fetal growth retardation 1, 2
- General PIH/gestational hypertension: Diuretics reduce plasma volume expansion, raising concerns they might promote the occurrence of pre-eclampsia 1
- The physiological basis: Pre-eclampsia is characterized by plasma volume reduction and increased systemic resistance, making volume depletion particularly problematic 3
When Diuretics May Be Used
Despite general avoidance, there are specific circumstances where diuretics have a role:
- Combination therapy: Diuretics should only be used in combination with other drugs, particularly when vasodilators exacerbate fluid retention, as they markedly potentiate the response to other antihypertensive agents 1
- Volume overload states: Diuretics are not recommended for blood pressure management in pregnancy but may be used during late-stage pregnancy if needed for volume management 1
- Renal or cardiac failure: Furosemide has been used safely in pregnancy complicated by renal or cardiac failure 1
- Thiazide preference: If needed, a thiazide should be chosen over loop diuretics for chronic management 1
Guideline Consensus on First-Line Agents
Multiple international guidelines consistently recommend avoiding diuretics as first-line therapy 1:
- Preferred agents: Methyldopa, labetalol, and long-acting nifedipine are first-line choices 1
- Classification: Diuretics are listed as "not first-line agents" but "probably safe" 1
- Postpartum use: Diuretics may reduce milk production at higher doses and are generally not preferred in breastfeeding women 1
Important Clinical Caveats
Key distinction: The contraindication is strongest for pre-eclampsia with proteinuria and fetal growth restriction, where uteroplacental perfusion is already compromised 1, 2. For uncomplicated gestational hypertension without these features, diuretics are discouraged but not absolutely contraindicated 1, 4.
Practical approach: If a woman is already on a diuretic when pregnancy is discovered and has well-controlled blood pressure without pre-eclampsia, the diuretic may be continued cautiously while monitoring closely for signs of volume depletion or fetal compromise 1. However, switching to methyldopa, labetalol, or nifedipine is generally preferred 1, 5.