Diagnosing Preeclampsia – Key Definitions and ACOG Guidelines

WHAT IS IT?

Preeclampsia is a pregnancy specific hypertensive disease with multi-system involvement. It usually occurs after 20 weeks of gestation and can be superimposed on another hypertensive disorder. While preeclampsia was historically defined by the new onset of hypertension in combination with proteinuria, some women will present with hypertension and multisystemic signs in the absence of proteinuria. The presence of multisystemic signs is an indication of disease severity.

SUMMARY:

Diagnostic Criteria

Blood Pressure Criteria

• Hypertension – systolic BP > 140 mm hg or diastolic BP > 90 mm hg or both
  • On two occasions at least 4 hours apart after 20 weeks gestations with previously normal BP
  • Considered ‘mild’ until diastolic BP > 110mm hg or systolic BP ≥160 mm Hg
• Severe Hypertension – systolic BP > 160 mm hg or diastolic BP > 110 mm hg or both
  • Can confirm using a short time interval (e.g., minutes) to facilitate timely antihypertensive therapy

Note: Gestational Hypertension

• ACOG defines gestational hypertension as “hypertension without proteinuria or severe features develops after 20 weeks of gestation and blood pressure levels return to normal in the postpartum period”
• Caution and close follow-up is warranted as up to a half of women with gestational hypertension will go on to manifest signs an symptoms consistent with preeclampsia
• Women with severe gestational hypertension, even in the absence of proteinuria should be managed similar to women with severe preeclampsia
• ACOG states

Women with gestational hypertension with severe range blood pressures (a systolic blood pressure of 160 mm Hg or higher, or diastolic blood pressure of 110 mm Hg or higher) should be diagnosed with preeclampsia with severe features.

Proteinuria Criteria

• 24 hour urine collection >300 mg protein or
• Single voided urine protein/creatinine ratio ≥0.3
• Dipstick reading of 2+ (use only if other quantitative methods not available)

Preeclampsia Definitions

Preeclampsia

• Hypertension and proteinuria or
• In absence of proteinuria, new-onset hypertension with the new onset of any of the following
  • Thrombocytopenia: Platelets <100 x 10⁹/L
  • Renal insufficiency: serum creatinine >1.1 mg/dl or doubling of serum creatinine in the absence of other renal disease
  • Impaired liver function: Elevated blood concentrations of liver transaminases to twice normal concentration
  • Pulmonary edema
  • Neuro: Unexplained new-onset headache unresponsive to medication (without an alternative diagnosis) or visual symptoms

Preeclampsia with severe features

• Preeclampsia diagnosis, above, with any of the following
  • Severe hypertension
    • On two occasions at least 4 hours apart while on bed rest (unless already on antihypertensive therapy)
  • Thrombocytopenia: Platelets <100 x 10⁹/L
  • Impaired liver function (without an alternative diagnosis): Elevated liver transaminases greater than twice upper limit of normal or severe persistent right upper quadrant or epigastric pain not responsive to medications
  • Progressive renal insufficiency: serum creatinine >1.1 mg/dl or doubling of serum creatinine in the absence of other renal disease
  • Pulmonary edema
  • Neuro: Unexplained new-onset headache unresponsive to medication (without an alternative diagnosis) or visual symptoms

Note: The following are not diagnostic criteria for the diagnosis of preeclampsia or preeclampsia with severe features

• Clinically evident edema
• Rapid weight gain
• Massive proteinuria
  • Does not qualify as a ‘severe feature’
• Fetal growth restriction
  • ACOG states that while it is important to monitor fetal status, FGR in the setting of all other fetal assessment being within normal limits (e.g., AFV, Doppler), expectant management ‘may be reasonable’ if mother and fetus appear stable and no other clinical indication is present that would indicate the need for early delivery
• Uric acid
  • Hyperuricemia in hypertensive pregnancy is not a diagnostic marker, but is an important finding as a risk factor for adverse maternal and fetal outcomes
    • Small for gestational age (SGA) infant
    • Prematurity
    • Risk for adverse maternal outcomes if include patients with preeclampsia and risks increase with increasing concentration of uric acid
  • May be warranted in the setting of ‘diagnostic dilemmas’ such as diagnosing superimposed preeclampsia in the setting of chronic hypertension

Learn More – Primary Sources

ACOG Practice Bulletin 222: Gestational Hypertension and Preeclampsia

National Partnership for Maternal Safety Consensus Bundle on Severe Hypertension During Pregnancy and the Postpartum Period

Plasma uric acid remains a marker of poor outcome in hypertensive pregnancy: a retrospective cohort study

Pre-eclampsia: pathophysiology and clinical implications