How is hyperemesis gravidarum diagnosed in a pregnant patient?

Diagnosis of Hyperemesis Gravidarum

Hyperemesis gravidarum is diagnosed clinically when a pregnant woman presents with intractable nausea and vomiting leading to weight loss exceeding 5% of prepregnancy body weight, dehydration, and electrolyte imbalances, typically occurring before 22 weeks gestation 1.

Clinical Diagnostic Criteria

The diagnosis is primarily clinical and based on three key features:

• Weight loss >5% of prepregnancy weight
• Dehydration (evidenced by orthostatic hypotension, decreased skin turgor, dry mucous membranes)
• Electrolyte imbalances and ketonuria

This represents a severe form of nausea and vomiting of pregnancy (NVP) that affects 0.3%–2% of pregnant women 1.

Timing and Presentation

HG typically:

• Starts before week 22 of gestation
• Most commonly begins at 4–6 weeks
• Peaks at 8–12 weeks
• Resolves by week 16 in >50% of cases and by week 20 in 80% of cases
• Persists throughout pregnancy in approximately 10% of women 1

Essential History Components

Obtain specific information about:

• Previous pregnancies (women with prior HG have higher recurrence risk)
• Pre-existing conditions (diabetes mellitus, asthma, hyperthyroid disorders, psychiatric illness)
• Previous molar pregnancy
• Current pregnancy characteristics (singleton female or multiple male fetuses have higher association) 1

Physical Examination Findings

Focus on identifying:

• Signs of dehydration: orthostatic hypotension, decreased skin turgor, dry mucous membranes
• Malnutrition: weight loss, muscle wasting
• Neurologic deficits: assess for neuropathy or vitamin deficiency (particularly thiamine deficiency risk for Wernicke encephalopathy) 1

Laboratory Evaluation

Required laboratory workup includes 1:

• Electrolytes (assess for hypokalemia and other imbalances)
• Renal function (assess extent of dehydration)
• Liver enzymes (elevated in 40%–50% of HG patients)
• Nutritional markers (albumin, vitamin deficiencies)
• Thyroid function tests (gestational thyrotoxicosis commonly associated with HG due to elevated hCG) 2
• Urinalysis (ketonuria)

Imaging Studies

Abdominal ultrasonography is indicated to 1:

• Detect multiple or molar pregnancies
• Assess fetal growth
• Rule out hepatobiliary causes (gallstones)
• Exclude vascular complications (portal vein thrombosis)
• Rule out renal pathology

Severity Assessment Tool

Use the Motherisk Pregnancy-Unique Quantification of Emesis (PUQE) score to quantify severity 1:

• Score ≤6: mild
• Score 7–12: moderate
• Score ≥13: severe

This validated scoring system assesses nausea duration, vomiting frequency, and retching episodes over the past 12 hours.

Differential Diagnosis Considerations

Critical pitfall: HG is a diagnosis of exclusion. You must rule out other causes of severe nausea and vomiting 3:

• Gastrointestinal disorders (gastroenteritis, peptic ulcer disease, pancreatitis, hepatitis, cholecystitis)
• Genitourinary conditions (pyelonephritis, uremia)
• Metabolic disorders (diabetic ketoacidosis, hyperthyroidism, Addison disease)
• Neurologic conditions (increased intracranial pressure, migraines)
• Drug toxicity or intoxication
• Psychological disorders

The comprehensive laboratory and imaging evaluation helps exclude these alternative diagnoses 1.

Important Clinical Nuances

While jaundice and highly elevated liver enzymes can occur with HG 2, their presence mandates thorough investigation to exclude concurrent or pre-existing liver disease. Bilirubin levels as high as 7.1 mg/dL and ALT up to 676 U/L have been reported in confirmed HG cases, but these findings should prompt careful evaluation.

The diagnosis does not require any specific laboratory threshold—it remains fundamentally clinical, based on the triad of severe vomiting, significant weight loss, and dehydration with their metabolic consequences occurring in early pregnancy after excluding other pathology 1, 4.