Blood Pressure Criteria for Diagnosis of Hypertension in Pregnancy
Hypertension in pregnancy is diagnosed when systolic blood pressure (SBP) ≥ 140 mmHg and/or diastolic blood pressure (DBP) ≥ 90 mmHg, measured on at least two separate occasions or at least 15 minutes apart in cases of severe hypertension. 1
Diagnostic Criteria
The diagnosis should be based on the following criteria:
- Required measurements: At least two high blood pressure readings on two separate occasions 1
- Timing between measurements: At least 4 hours apart for mild to moderate hypertension, or at least 15 minutes apart for severe hypertension (≥160/110 mmHg) 1
- Measurement technique: Using Korotkoff phase V (disappearance of sound) for diastolic blood pressure, with phase IV only indicated if sounds persist to near zero 1
Classification of Blood Pressure Values
| Classification | Definition |
|---|---|
| Normal | SBP <140 mmHg AND DBP <90 mmHg |
| Mild to moderate hypertension | SBP 140-159 mmHg OR DBP 90-109 mmHg |
| Severe hypertension | SBP ≥160 mmHg OR DBP ≥110 mmHg |
Types of Hypertension in Pregnancy
Pre-existing (chronic) hypertension:
- BP ≥140/90 mmHg that predates pregnancy or develops before 20 weeks gestation 1
- Usually persists >42 days postpartum
Gestational hypertension:
- New-onset hypertension after 20 weeks gestation
- Without proteinuria or other features of preeclampsia 1
Preeclampsia:
- Gestational hypertension with proteinuria (≥0.3 g/day) OR
- Gestational hypertension with evidence of maternal organ dysfunction 1
Pre-existing hypertension with superimposed gestational hypertension and proteinuria:
- Worsening of pre-existing hypertension with new proteinuria or organ dysfunction 1
Important Considerations
- The older criterion of "increase of 30/15 mmHg compared to first visit BP" is no longer recommended; absolute values (≥140/90 mmHg) are now preferred 1, 2
- Mean Arterial Pressure (MAP) increase is not part of current diagnostic criteria 1
- 24-hour ambulatory blood pressure monitoring (ABPM) is superior to conventional measurements for predicting outcomes but is not required for diagnosis 1, 2
- Normal values for 24-hour ABPM before 22 weeks: 24-hour average <126/76 mmHg; awake average <132/79 mmHg; sleep average <114/66 mmHg 1, 2
- Home BP monitoring can be useful but devices should be validated against a calibrated sphygmomanometer 1, 2
Clinical Implications
- Severe hypertension (SBP ≥160 mmHg or DBP ≥110 mmHg) requires immediate treatment due to increased risk of stroke and other adverse maternal outcomes 1
- Women with hypertension in pregnancy should undergo baseline testing including complete blood count, liver enzymes, renal function, and urinalysis to monitor for development of preeclampsia 1
- Up to 25% of women with chronic hypertension will develop superimposed preeclampsia 2
Pitfalls to Avoid
- Do not rely on a single elevated reading for diagnosis
- Do not use the outdated criterion of relative increase from baseline BP
- Do not wait for proteinuria to diagnose preeclampsia if other signs of organ dysfunction are present
- Do not use unvalidated home BP devices without checking their accuracy
- Do not delay treatment when severe hypertension (≥160/110 mmHg) is detected
The International Society for the Study of Hypertension in Pregnancy (ISSHP) and European Society of Cardiology guidelines provide the most current and comprehensive criteria for diagnosing hypertension in pregnancy, emphasizing absolute BP values ≥140/90 mmHg measured on multiple occasions.