Hyperemesis Gravidarum: Severe Morning Sickness Explained

What is hyperemesis gravidarum?

Hyperemesis gravidarum (HG) is a severe form of pregnancy sickness that goes far beyond ordinary morning sickness. While most pregnant people experience some nausea in the first trimester, HG causes persistent, excessive vomiting that can lead to dehydration, weight loss, and the inability to carry out normal daily activities.

HG affects approximately 1-3% of pregnancies. It typically begins between weeks 4 and 7, peaks around weeks 9 to 13, and for most people gradually improves by week 20. However, around 20% of those affected continue to experience symptoms throughout their entire pregnancy.

It is important to be clear: HG is not simply "bad morning sickness." It is a recognised medical condition that can have serious consequences if left untreated, including severe dehydration, malnutrition, and significant impact on mental health.

How to recognise HG

The key differences between ordinary morning sickness and HG include:

Vomiting frequency and severity. With HG, vomiting is persistent and often relentless, sometimes more than 10 times a day. Unlike typical morning sickness where you can usually keep some food and fluids down, HG can make it impossible to keep anything in your stomach.

Weight loss. Losing more than 5% of your pre-pregnancy body weight is a clinical marker for HG. Many people lose considerably more.

Dehydration. Dark urine, infrequent urination, dizziness when standing, dry mouth, and feeling faint are all signs. Severe dehydration requires medical intervention with IV fluids.

Inability to function. HG is debilitating. Many people cannot work, care for other children, or carry out basic daily tasks. The constant nausea and vomiting can make it difficult to even get out of bed.

Ketosis. When your body cannot get enough energy from food, it starts breaking down fat reserves, producing ketones. This can be detected in a urine test and is a sign that your body needs nutritional support.

Getting treatment in the UK

If you suspect you have HG, contact your GP or maternity unit as early as possible. Early treatment prevents the condition from worsening. Do not wait until you are severely dehydrated before seeking help.

Anti-sickness medication. Several antiemetic medications are considered safe in pregnancy and can be prescribed by your GP. These include cyclizine, prochlorperazine, metoclopramide, and ondansetron. Your doctor will discuss the options with you. If the first medication does not work, ask about trying a different one or combining treatments.

IV fluids. If you are dehydrated and cannot keep fluids down, you may need intravenous fluids. This can be done as a day case at hospital or, in some areas, through ambulatory care where you receive IV fluids and go home the same day.

Hospital admission. Severe cases may require a hospital stay for IV fluids, IV anti-sickness medication, and monitoring. Some people need multiple admissions throughout their pregnancy.

Thiamine (vitamin B1) supplementation. Prolonged vomiting can deplete thiamine levels, which in rare cases can lead to Wernicke's encephalopathy, a serious neurological condition. Your care team should consider thiamine supplementation if you have been vomiting for an extended period.

The mental health impact

The psychological toll of HG is enormous and often underestimated. Research has found that people with HG experience rates of depression and anxiety comparable to those with chronic pain conditions. Many describe feelings of isolation, guilt, grief for the pregnancy experience they expected, and frustration at not being taken seriously.

If you are struggling mentally, please tell your midwife or GP. You deserve support for your emotional wellbeing as well as your physical symptoms. Perinatal mental health support is available and you should not have to cope with this alone.

Some people with severe HG make the difficult decision to terminate the pregnancy because of the severity of their symptoms. If you are feeling this way, please speak to your care team. Better treatment options may be available, and specialist support exists.

What you can try at home

Home management of HG is limited compared to ordinary morning sickness, because the severity of the condition usually requires medical intervention. However, some strategies may help alongside your prescribed treatment:

Sip small amounts of fluid frequently rather than trying to drink large volumes. Ice lollies and frozen fruit can sometimes be tolerated when liquids cannot. Eat whatever you can, whenever you can, without worrying about nutrition at this stage (your prenatal vitamin and your body's stores will cover the baby's needs). Rest as much as possible, as fatigue worsens nausea. Keep a basin by your bed and supplies within reach to minimise movement. Accept all offers of help.

Will my baby be OK?

This is the question every person with HG asks. The reassuring answer is that in most cases, babies are not harmed by HG, even when the mother is very unwell. Your baby draws nutrients from your existing reserves, and the human body is remarkably good at prioritising the pregnancy even when you feel terrible.

Severe, untreated HG with significant weight loss can be associated with lower birth weight, but this risk is substantially reduced with appropriate treatment. Getting medical help early and staying on top of your hydration and anti-sickness medication is the best thing you can do for both yourself and your baby.

Getting support

The Pregnancy Sickness Support charity (pregnancysicknesssupport.org.uk) is the UK's dedicated HG support organisation. They offer a helpline, peer support, and resources for both affected individuals and healthcare professionals. The Hyperemesis Education and Research Foundation (hyperemesis.org) also provides evidence-based information and a global support community.

If you feel that your symptoms are being dismissed or not taken seriously by your care team, you have the right to ask for a second opinion or to be referred to a specialist. HG is a medical condition that deserves proper treatment, not dismissal.