What are the diagnostic criteria for postpartum hypertension versus normal physiologic changes?

Diagnostic Criteria for Postpartum Hypertension vs. Normal Physiologic Changes

Postpartum hypertension is definitively diagnosed as systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg on 2 or more occasions at least 4 hours apart during the postpartum period. 1

Normal Physiologic Blood Pressure Changes Postpartum

In normal pregnancy, blood pressure:

• Falls to a nadir between 20-24 weeks gestation
• Gradually increases until term when pre-pregnancy values are achieved 2
• Returns to pre-pregnancy levels after delivery in uncomplicated pregnancies

Diagnostic Algorithm for Postpartum Hypertension

Step 1: Blood Pressure Measurement Criteria

• Hypertension threshold: SBP ≥140 mmHg and/or DBP ≥90 mmHg 2
• Confirmation requirement: Measurements on 2 or more occasions at least 4 hours apart 1
• Severe hypertension: SBP ≥160 mmHg and/or DBP ≥110 mmHg on 2 or more occasions repeated at a short interval (minutes) 1

Step 2: Timing Classification

• Pre-existing hypertension: Hypertension that was present before pregnancy or developed before 20 weeks gestation and persists >42 days postpartum 2
• Gestational hypertension/preeclampsia: May persist into postpartum period but should resolve within 6-12 weeks postpartum 2
• De novo postpartum hypertension: New onset hypertension that develops after delivery 3

Step 3: Evaluate for Preeclampsia Features

Postpartum preeclampsia is diagnosed when hypertension is accompanied by one or more of:

• Proteinuria (>0.3 g/24h or ACR ≥30 mg/mmol) 2
• Evidence of maternal organ dysfunction:
  • Acute kidney injury
  • Liver involvement
  • Neurological complications (severe headaches, visual disturbances)
  • Hematological complications (thrombocytopenia) 2
• HELLP syndrome (hemolysis, elevated liver enzymes, low platelets) 2

Important Clinical Considerations

1. Timing of evaluation: Reassessment is necessary at or after 42 days postpartum to distinguish between persistent gestational hypertension and chronic hypertension 2

2. Iatrogenic causes to rule out:

   • NSAIDs for postpartum analgesia
   • Ergot derivatives for postpartum hemorrhage
   • Ephedrine used to correct hypovolemia after regional anesthesia 2

3. Warning signs requiring immediate attention:

   • SBP >160 mmHg sustained over 15 minutes
   • Tachycardia
   • Oliguria 2

4. Secondary causes should be investigated in cases of:

   • Severe or resistant hypertension
   • Hypokalemia
   • Abnormal creatinine
   • Strong family history of renal disease 1

Clinical Pitfalls to Avoid

1. Underdiagnosis: Postpartum hypertension affects approximately 2% of pregnancies but is often underrecognized 1. Only 44.6% of women with hypertensive disorders of pregnancy correctly identify systolic BP of 140 as the threshold to contact a clinician 4.

2. Delayed treatment: Severe hypertension sustained over 15 minutes should be treated immediately to prevent maternal stroke and other complications 1.

3. Inadequate monitoring: Women with hypertensive disorders of pregnancy should have more frequent BP monitoring in the postpartum period, including home BP monitoring when appropriate 4.

4. Misattribution to normal physiologic changes: Normal postpartum blood pressure should not exceed 140/90 mmHg; readings above this threshold require evaluation and should not be dismissed as normal physiologic changes 2.

5. Missing preeclampsia: Remember that preeclampsia can develop de novo in the postpartum period, even without prior hypertension during pregnancy 2.

By following this diagnostic algorithm and being aware of the potential pitfalls, clinicians can accurately differentiate between postpartum hypertension requiring intervention and normal physiologic changes.