Patients with gestational hypertension are at increased risk for preeclampsia, HELLP syndrome, preterm birth, small-for-gestational-age infants, and placental abruption. Risk factors include obesity, use of assisted reproductive technology, prior preeclampsia, and multifetal gestation. Older maternal age and obesity contribute to increasing incidence. Close monitoring is essential to detect progression to severe hypertension or preeclampsia, particularly in those diagnosed before 34 weeks, those with systolic BP greater than 135 mm Hg, or those with a history of miscarriages.

Case Definitions^1,2

Chronic hypertension: Hypertension (140/90 mm Hg or greater) presents before pregnancy or is diagnosed before the 20th week of gestation.

Superimposed preeclampsia: A patient with chronic hypertension who has passed after the 20th week of gestation and develops new-onset proteinuria (protein/creatinine 0.3 or greater; urine dipstick 2+ or greater) or other signs of end-organ dysfunction such as:

Renal insufficiency: Creatinine levels greater than 1.1 mg/dL or a doubling of baseline creatinine

BP worsening: Typically, 160/110 mm Hg or greater, despite previously controlled chronic hypertension

Thrombocytopenia: Platelet count less than 100×10⁹/L

Impaired liver function: Elevated AST/ALT [aspartate aminotransferase/alanine aminotransferase] twice the upper limit of normal, often associated with right upper quadrant or epigastric pain

Pulmonary edema: New-onset fluid accumulation in the lungs

Neurological symptoms: Persistent severe headache, vision changes, or altered mental status

Gestational hypertension: New-onset hypertension (140/90 mm Hg or greater) after 20 weeks of pregnancy in a previously normotensive patient. It differs from preeclampsia because it does not include proteinuria OR signs of end-organ dysfunction.

Severe gestational hypertension: BP at severe levels (160/110 mm Hg or greater), which remains elevated despite initial management efforts. Although the condition may lead to preeclampsia, it differs because it occurs without proteinuria or systemic findings of end-organ dysfunction.

Preeclampsia: Gestational hypertension AND either proteinuria OR systemic signs. Severe preeclampsia includes severe hypertension (systolic BP160 mm Hg or greater or diastolic BP 110 mm Hg or greater), significant proteinuria, and evidence of organ dysfunction). It can occur at any time after 20 weeks but is more common after 34 weeks.

HELLP syndrome: Serum aminotransferase levels 70 U/L or greater, platelet count less than 100×10⁹/L, and LDH less than 600 U/L. HELLP affects less than 1 percent of pregnancies but has a seven percent to 70 percent perinatal mortality rate and a one percent to 24 percent maternal mortality rate.3 Symptoms are nonspecific, including nausea, vomiting, and abdominal pain.