Hyperemesis Gravidarum (HG)

What Is Hyperemesis Gravidarum?

Hyperemesis gravidarum (HG) is the most severe form of nausea and vomiting in pregnancy. It goes far beyond typical "morning sickness." HG causes persistent, excessive vomiting that leads to dehydration, weight loss, electrolyte imbalances, and the inability to carry out normal daily activities. It affects approximately 1-3% of pregnancies.

HG is a recognised medical condition with ICD-10 diagnostic codes (O21.0 and O21.1). It is not "bad morning sickness," it is not psychological, and it is not caused by not wanting the baby. It is a physiological condition that requires medical treatment.

Diagnostic Criteria

There is no single definitive test for HG. Diagnosis is clinical, based on the following criteria:

• Persistent, excessive vomiting: Not related to other causes (UTI, thyroid disorder, etc.)
• Weight loss: Greater than 5% of pre-pregnancy body weight
• Dehydration: Evidenced by dark urine, dry mouth, reduced urine output, dizziness
• Ketosis: Ketones present in urine (tested with a dipstick), indicating the body is breaking down fat due to insufficient food intake
• Electrolyte imbalance: Abnormal blood tests (low potassium, low sodium)
• Functional impairment: Unable to work, care for self or family, or maintain normal activities

The PUQE Score

Healthcare professionals may use the Pregnancy-Unique Quantification of Emesis (PUQE) score to assess severity. It measures three things over a 24-hour period:

1. How many hours of nausea did you experience?
2. How many times did you vomit?
3. How many times did you retch/dry heave?

A PUQE score of 13 or above indicates severe NVP/HG requiring active treatment.

What Happens in Hospital

If you're admitted to hospital with HG, here's what typically happens:

Assessment

• Urine test for ketones and infection
• Blood tests for electrolytes (potassium, sodium), kidney function, liver function, and thyroid
• Weight check and comparison to pre-pregnancy weight
• Assessment of dehydration level
• Ultrasound if not yet performed (to confirm viable pregnancy and check for multiple pregnancy or molar pregnancy)

Treatment

• IV fluids: Normal saline or Hartmann's solution to rehydrate you. This often brings significant relief within hours. You may need 2-4 litres over 24 hours.
• IV anti-sickness medication: Faster and more effective than oral medication when you can't keep tablets down. Commonly ondansetron, cyclizine, or metoclopramide given intravenously.
• Electrolyte replacement: Potassium and other electrolytes may be added to your IV fluids if blood tests show deficiencies.
• Thiamine (vitamin B1): Given to prevent Wernicke's encephalopathy, a rare but serious complication of prolonged vomiting and malnutrition.
• Thromboprophylaxis: Blood-thinning injections (such as enoxaparin) may be given because dehydration and immobility increase the risk of blood clots.

Discharge

You'll typically be discharged when you can keep fluids and oral medication down, your ketones have cleared, and you feel stable enough to manage at home. You should go home with a prescription for anti-sickness medication and a clear plan for when to return.

Complications of Untreated HG

When HG is not adequately treated, it can lead to:

• Severe dehydration: Dangerous for both mother and baby
• Malnutrition: Depletion of essential vitamins and minerals
• Wernicke's encephalopathy: Brain damage from thiamine (B1) deficiency — preventable with supplements
• Muscle wasting: From prolonged inability to eat adequately
• Depression and anxiety: Very common with HG and may persist postnatally
• PTSD: Some women develop post-traumatic stress from the severity of their experience
• Damage to tooth enamel: From repeated exposure to stomach acid
• Oesophageal tears: Mallory-Weiss tears from forceful vomiting (rare)

Impact on Baby

Many women with HG worry about the effect on their baby. The reassuring news is that with appropriate treatment, babies of HG mothers generally do well. However:

• Babies may be slightly lower birth weight, particularly if HG persists throughout pregnancy without adequate treatment
• There is a small increased risk of preterm birth in severe, untreated cases
• Adequate hydration and nutrition (even if supported by IV fluids) significantly reduces any risk to the baby
• Anti-sickness medications used to treat HG have not been shown to cause harm to babies

The key message: treating HG protects both you and your baby. Not treating it carries more risk than the treatment itself.

HG and Mental Health

HG has a devastating impact on mental health. Studies show that:

• Nearly 50% of women with HG experience depression during pregnancy
• Up to 18% of women with HG have considered termination solely because of the severity of their sickness
• Many women with HG develop PTSD-like symptoms
• HG affects bonding with the baby — which is a normal response to trauma, not a reflection of your love for your child
• Some women choose not to have more children because of their HG experience

If you're experiencing thoughts of self-harm, overwhelming despair, or are considering termination because of HG, please reach out for help immediately. Contact your GP, midwife, the Samaritans (116 123), or the Pregnancy Sickness Support helpline (024 7569 0504).

Future Pregnancies

If you've had HG in one pregnancy, you have approximately a 15-20% chance of experiencing it again, though some studies suggest the recurrence can be higher. However, severity can vary. Many women who had HG find that:

• Starting medication early (even before symptoms begin) can reduce severity
• Having a treatment plan in place before conception reduces anxiety and improves outcomes
• Different pregnancies can behave differently — HG is not guaranteed to recur
• Support from healthcare providers who understand HG makes a significant difference