Hyperemesis Gravidarum (Severe Pregnancy Sickness)

Hyperemesis gravidarum vs morning sickness

Up to 80% of pregnant people have some nausea or vomiting, usually called morning sickness. Hyperemesis gravidarum is at the far end of that spectrum.

Symptoms

• severe, constant nausea that is often not relieved by vomiting
• vomiting many times a day, sometimes with streaks of blood from a strained esophagus
• being unable to keep food, water or tablets down
• weight loss
• signs of dehydration: thirst, dry mouth, dark and infrequent urine, headache, dizziness on standing, a fast heart rate
• excess saliva (ptyalism) and spitting
• extreme fatigue and weakness
• strong sensitivity to smells, movement and light
• low mood, anxiety and isolation

Causes and risk factors

HG is linked to pregnancy hormones. Research published in 2023 showed that GDF15, a hormone made mainly by the placenta, plays a major role. People who are more sensitive to GDF15, or have very high levels, are more likely to develop HG. High levels of hCG, the pregnancy hormone, also contribute.

Risk is higher with:

• HG in a previous pregnancy (it often recurs)
• a mother or sister who had HG
• multiple pregnancy (twins or more)
• a molar pregnancy
• a history of motion sickness or migraine
• a first pregnancy

HG is not caused by stress or anxiety, and it is not "in your head".

How it is diagnosed

HG is diagnosed from your symptoms once other causes are ruled out. Your provider will:

• weigh you and compare it with your pre-pregnancy weight
• check your pulse, blood pressure and urine for ketones (a sign the body is breaking down fat)
• order blood tests for sodium, potassium, kidney and liver function, blood count and sometimes thyroid levels
• arrange an ultrasound to check for twins or a molar pregnancy
• use a severity score such as the PUQE score, which rates nausea, vomiting and retching over 24 hours

Vomiting that starts after 10 weeks, or comes with fever, belly pain, headache or a swollen neck, suggests another cause such as a urinary infection, gastroenteritis, gallbladder or thyroid disease.

Treatment

Treatment follows a step-by-step approach and should start early. Treating moderate symptoms promptly can stop them becoming severe.

Medicines

• Vitamin B6 (pyridoxine), with or without doxylamine: first-line treatment, available as a combination prescription tablet.
• Antihistamines such as promethazine, cyclizine or dimenhydrinate.
• Dopamine antagonists such as metoclopramide or prochlorperazine.
• Ondansetron: effective. Your provider can discuss the very small possible risk in early pregnancy.
• Corticosteroids: for severe HG that does not respond to other treatment, usually after 10 weeks.
• Acid-reducing medicines to ease heartburn and stomach irritation from repeated vomiting.

These medicines have been widely used in pregnancy. Untreated severe vomiting poses greater risks to you and your baby than the medicines do.

Fluids and vitamins

• IV fluids replace water, sodium and potassium. Many people are treated as day patients or at home with infusion services.
• Thiamine (vitamin B1): given to anyone with prolonged vomiting, before sugar-containing fluids, to prevent Wernicke encephalopathy, a serious brain complication.
• Switching to a folic acid-only supplement can help if a full prenatal vitamin triggers vomiting.

Nutrition support

When weight loss continues despite treatment, a feeding tube through the nose or, rarely, intravenous nutrition is used.

Hospital care

Admission is advised when you cannot keep fluids or medicines down, have significant ketones or electrolyte problems, or are losing weight despite treatment. Hospital stays often include blood-thinning injections to prevent blood clots, because dehydration and immobility raise the risk.

Self-help that can ease symptoms

• Eat small amounts often, whatever you can tolerate. Bland, salty or cold foods are often easier.
• Drink small sips between meals rather than with them.
• Rest, and avoid smells and triggers where possible.
• Ginger and acupressure wristbands may help mild symptoms, but they are not enough on their own for HG.
• Ask for help with work, childcare and meals.

Complications

For you:

• dehydration and acute kidney injury
• low potassium (hypokalemia) and low sodium, which can affect heart rhythm
• vitamin deficiencies, especially thiamine
• tears of the esophagus from repeated retching
• blood clots
• depression, anxiety and, after pregnancy, post-traumatic stress symptoms

For the baby, well-treated HG has a good outcome. Prolonged, poorly controlled HG with ongoing weight loss is linked with lower birth weight and preterm birth.

Recovery and future pregnancies

Most people feel noticeably better between 16 and 20 weeks, and symptoms usually stop soon after birth. Fatigue and emotional effects can last longer, and support from your provider or a mental health professional can help.

HG often comes back in later pregnancies. Planning ahead helps: discuss starting medicines as soon as you know you are pregnant, or even before symptoms begin.

Frequently asked questions

How do I know if I have hyperemesis gravidarum or morning sickness?

Morning sickness is unpleasant but you can still keep down enough food and fluids. With HG you vomit frequently, cannot keep food or drink down, lose weight, become dehydrated and often cannot carry out normal daily activities. If you are unsure, contact your provider for a check of your weight, urine and blood.

When does hyperemesis gravidarum start and end?

It usually starts between 4 and 6 weeks of pregnancy, peaks around 9 to 13 weeks and improves for many people by 16 to 20 weeks. Some people have symptoms until delivery. Symptoms almost always stop within days of giving birth.

Can hyperemesis gravidarum harm my baby?

With good treatment, most babies are born healthy. The risk is higher with severe, untreated HG that causes ongoing weight loss, which is linked with low birth weight and preterm birth. Getting treatment early with medicines, fluids and vitamins protects both you and your baby.

What is the best medicine for hyperemesis gravidarum?

There is no single best medicine. Treatment usually starts with vitamin B6 and doxylamine, then adds or switches to antihistamines, metoclopramide, prochlorperazine or ondansetron, with steroids for severe cases. Your provider will adjust the combination until symptoms are controlled.

Will I get hyperemesis gravidarum again?

There is a high chance it will recur in a future pregnancy, although severity can differ. Talk to your provider before your next pregnancy so you can start anti-sickness medicine early and have a plan for fluids and support ready.

What causes hyperemesis gravidarum?

It is linked to pregnancy hormones, particularly GDF15, made by the placenta, and hCG. Genetics plays a role, which is why it runs in families. Carrying twins or a molar pregnancy raises the risk. It is a physical condition, not a psychological one.