Hyperemesis Gravidarum: A Clinical Reference for Providers

A clinical reference for obstetric, midwifery, primary care, and emergency clinicians. If you are a patient looking for a plain-language explanation, start with our complete guide to hyperemesis gravidarum.

Hyperemesis gravidarum (HG) remains underdiagnosed and undertreated, largely because legacy definitions require weight loss before treatment begins. This page collects the diagnostic criteria, the current science, the validated scoring tools, published treatment algorithms, and the protocol we use at Materna, so that colleagues can act earlier and with more confidence.

As Kristin Mallon, CNM and co-founder of Materna, puts it:

“Hyperemesis is a debilitating, physiological condition, not a psychological weakness, not morning sickness, and absolutely not something women should suffer through.”

Diagnostic criteria: the Windsor definition

HG is best defined using the Windsor definition, which is more clinically useful than criteria anchored to weight loss. HG is diagnosed when all of the following are present:

1. Severe, debilitating nausea and vomiting beginning before 16 weeks
2. Inability to eat or drink normally, leading to malnutrition or dehydration
3. Substantial impact on daily functioning, work, or basic self care
4. No alternative diagnosis explaining the symptoms

Many patients meet these criteria considerably earlier than legacy definitions allow, and earlier recognition changes outcomes.

Prevalence: higher than the textbooks suggest

Up to 90% of pregnant patients experience some nausea and vomiting. HG is categorically different: more intense, more disabling, and more likely to result in admission. HG alternates with early bleeding as the leading cause of early pregnancy hospital admission.

Official prevalence is usually cited at 0.3% to 3%. Newer research and clinical observation suggest 10% to 15% is closer to reality. The gap is explained by underdiagnosis, symptom dismissal, and definitions that require weight loss before intervention.

Pathophysiology: GDF-15 and IGFBP-7

The hCG hypothesis has largely been displaced. Current understanding, published in Nature and other leading journals, implicates two fetal-placental hormones:

• GDF-15
• IGFBP-7

Patients who develop HG appear to have genetic sensitivity to GDF-15, higher placental production of these hormones, or both. This accounts for three clinical observations:

• HG runs in families
• Severity tends to be similar or worse in subsequent pregnancies
• Patients with baseline elevated GDF-15, as in certain chronic conditions, may present more severely

It also opens the possibility of future preconception therapeutics. Desensitization using metformin or berberine has appeared in early research, but the evidence is preliminary and further study is needed before it can be recommended.

Objective scoring: HELP and PUQE

Objective scoring is the single most useful change a practice can make. It replaces impression with measurement and it documents functional impact, which matters for both treatment escalation and workplace accommodation.

HELP Score (HER Foundation)

Categorizes severity and guides treatment escalation. Reference: HER Foundation HELP Score. Patients can also complete Materna’s HELP Assessment before a visit, which gives you a severity score at intake.

PUQE Score (12 hour and 24 hour)

Validated scale for nausea and vomiting severity. Reference: PUQE score.

“Once we quantify HG, clinicians can finally follow evidence instead of intuition. It takes the guesswork out and brings HG into the medical mainstream.”

Published treatment algorithms and guidelines

• HER Foundation: treatment overview and algorithm
  hyperemesis.org treatment
• RCOG Green-top Guideline No. 69
  RCOG guideline 69
• NICE: nausea and vomiting in pregnancy
  NICE CG62
• ACOG Practice Bulletin No. 189
  ACOG practice bulletins

The Materna protocol

Materna uses an early, aggressive, layered protocol, drawing on ACOG, RCOG, HER Foundation, CMAJ, and peer-reviewed research.

• Frequent visits, two to three times per week
• IV hydration plus vitamins: thiamine (B1), folate, B-complex
• Combination antiemetic therapy rather than monotherapy
• Acid suppression
• Nutrient support
• Mental health screening
• Objective scoring at every visit

Thiamine before dextrose. This is not a minor sequencing detail. Administering dextrose before thiamine can precipitate Wernicke encephalopathy in a depleted patient. We cover the mechanism in thiamine deficiency in hyperemesis gravidarum and preventing Wernicke encephalopathy.

Based on our internal chart reviews, 99% of the hyperemesis patients we treat at Materna stay out of the emergency room.

Risks of undertreatment

Maternal

• Electrolyte imbalance
• Wernicke encephalopathy from B1 deficiency
• Nutritional deficiencies
• Gallbladder disease
• GI disorders
• Long-term cardiovascular impacts
• PTSD in approximately 18% of patients with HG, with more than half reporting trauma symptoms (HER Foundation)

The psychiatric burden is frequently missed. See hyperemesis gravidarum, anxiety, depression, and PTSD for screening guidance and what to say to a patient who is still unwell.

Fetal and neonatal

• Preterm birth
• Low birth weight
• NICU admission
• Small for gestational age
• Neural tube defects from vitamin depletion
• Possible increase in neurodevelopmental disorders

These risks are substantially preventable with early diagnosis and effective treatment. For the longer horizon, see long-term effects of hyperemesis gravidarum on mothers and children.

Preconception care for patients with an HG history

Because severity tends to recur, preconception planning is one of the highest-yield interventions available.

• Full health assessment
• H. pylori testing, and treatment if positive
• Review and correction of underlying GI, nutrient, or endocrine issues
• Discussion of prophylactic medications
• Nutrient and lifestyle optimization
• A written pregnancy action plan agreed before conception

Nutrition is central. Our hyperemesis gravidarum dietary guide covers practical intake when very little stays down. See also HER Foundation prevention.

Clinician checklist

• Use an objective score at every visit
• Give IV fluids and thiamine before dextrose
• Layer medications early: doxylamine and pyridoxine, plus metoclopramide, plus an acid reducer
• Check electrolytes regularly
• Follow up every 24 to 72 hours until stable
• Document how symptoms limit daily life, not weight alone
• Avoid dismissive framing such as “it is normal” or “it is part of pregnancy”
• Screen for anxiety, depression, and trauma symptoms

Patient checklist to share

• Track symptoms with PUQE or the HELP Score
• Begin hydration immediately, electrolytes over plain water
• Take thiamine (B1), do not wait
• Contact an HG-literate clinician
• Request early medication layering, not sequential single-drug trials
• Do not rely on herbal remedies as primary treatment; ginger is not therapeutic at this severity
• Arrange practical support for food, childcare, and transport
• Monitor mental health closely

Resource library

Core clinical guidelines

• CMAJ HG clinical practice updates
• RCOG Green-top Guideline
• ACOG Practice Bulletin, NVP and HG
• Pregnancy Sickness Support, UK

Tools and scores

• HELP Score
• Materna HELP Assessment
• PUQE Score

Patient-facing resources

• HER Foundation
• Pregnancy Sickness Support
• Materna HG education hub
• Materna HG webinar recording

Referring a patient to Materna

Materna is the Hyperemesis Treatment Center of NYC. We offer same-week evaluation, HG scoring and diagnosis, IV hydration and vitamin therapy, evidence-based medication protocols, nutrition support, mental health screening, frequent follow-up, preconception counseling, and virtual visits for patients outside New York.

Refer a patient using our provider referral form, or have the patient book an HG consult directly.

Frequently asked questions

How is HG distinguished from nausea and vomiting of pregnancy?

Severity and function. Nausea and vomiting of pregnancy is uncomfortable but does not prevent adequate oral intake or daily functioning. HG does, producing dehydration, nutritional depletion, and inability to manage ordinary life. The Windsor criteria formalize this distinction without requiring weight loss first.

When should thiamine be given?

Before dextrose, in any patient with prolonged poor intake. Administering glucose to a thiamine-depleted patient can precipitate Wernicke encephalopathy. Thiamine is inexpensive, safe, and should not wait for confirmatory testing.

Does hyperemesis gravidarum affect the baby?

When HG is treated early and adequately, most infants are born healthy. Fetal risks including low birth weight and preterm birth rise mainly when HG is undertreated and the patient becomes dehydrated and nutritionally depleted.

Is hyperemesis gravidarum a disability?

HG is not automatically classified as a disability, but its functional impact often meets the threshold for workplace accommodation. Documentation of functional limitation, rather than weight change alone, is what supports an accommodation request. See navigating hyperemesis gravidarum at work.

Do you accept out-of-area referrals?

Yes. We offer virtual consults for patients anywhere in the United States, and same-week in-person evaluation in Manhattan.

“No one should face HG alone. With the right care, women can reclaim their pregnancies and their daily lives.”
Kristin Mallon, CNM