Hyperemesis gravidarum (HG)

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What is hyperemesis gravidarum (HG)? 

Causes of hyperemesis gravidarum

Symptoms of hyperemesis gravidarum

Hyperemesis gravidarum and blood clots 

Treatment for hyperemesis gravidarum 

Will hyperemesis gravidarum harm my baby?

Hyperemesis gravidarum and mental health

Hyperemesis gravidarum and work

What is hyperemesis gravidarum?

Hyperemesis gravidarum (HG) is a very severe form of pregnancy sickness (also known as morning sickness). You may be sick many times a day and not be able to keep food or drink down. HG often needs hospital treatment.  

HG is thought to affect around 1 to 3 in every 100 pregnancies.

Causes of hyperemesis gravidarum

Research suggests that HG is caused by a hormone called GDF15.

We have the hormone GDF15 in our body all the time. Some people naturally have higher levels of it in their blood than others.  GDF15 is also released in pregnancy. Women and birthing people who are more sensitive to this hormone are more likely to get hyperemesis gravidarum in pregnancy.  

One of the reasons some women and birthing people are more sensitive to GDF15 is because they have a gene mutation that means they have very low levels of GDF15 in their blood before pregnancy. This means they get an extreme reaction to the hormone when it is released by their body in pregnancy.

People with high levels of GDF15 in their blood all the time do not seem to be as affected by nausea and vomiting in pregnancy.

There is some evidence that you are more likely to have HG if:

• you have a mother or sister who has had it
• you have suffered with HG before.

Symptoms of hyperemesis gravidarum

Symptoms of HG include:

• extreme nausea (feeling extremely sick)
• regular vomiting (being sick)
• weight loss
• dehydration
• low blood pressure (hypotension)
• changes to your sense of smell
• producing more saliva.

Dehydration can cause:

• thirst
• tiredness
• not weeing very much
• dark yellow and strong-smelling wee
• headaches and constipation.

Symptoms of low blood pressure include:

• lightheadness or dizziness
• blurred vision
• generally feeling weak  
• fainting.

Symptoms are usually worst at 9-13 weeks. They may improve around 16-24 weeks but may continue throughout the whole pregnancy.

Hyperemesis gravidarum and blood clots

Because HG can cause dehydration, there's also an increased risk of having a blood clot (deep vein thrombosis). 1-2 in 1000 pregnant women and birthing people will get a blood clot in their vein during, or in the first 6 weeks after, pregnancy.

If you are dehydrated and unable to move around much due to HG, you may be offered treatment to help prevent a blood clot. Read more about deep vein thrombosis in pregnancy.

Treatment for hyperemesis gravidarum

If you’re being sick a lot or can’t keep your food or drink down, tell your midwife or GP, or contact your local maternity unit as soon as possible. They can make sure you get the right treatment, so you don’t get dehydrated.  

You may need to go into hospital for treatment.  If needed, you can be given fluid and medicines into a vein (intravenously) to help you stay hydrated.

There are several medicines that research says are safe to use in pregnancy. These include anti-sickness drugs (anti-emetics), vitamins B6 and B12, steroids or a combination of these. Do not take any medicine for HG without speaking to a midwife or doctor first.

The Best Use of Medicine in Pregnancy (BUMPS) website has more information on different drugs and what we know about their safety and side effects.  

Research suggests that anti-sickness medications work better the sooner they are started.

You can read more about treatments on the Pregnancy Sickness Support website.  

Some anti-sickness medication suitable in pregnancy cannot be taken with some types of anti-depressants. Ask your doctor to explain more about your options if you take anti-depressants and need anti-sickness medication too.

Will hyperemesis gravidarum harm my baby?

It’s unlikely that having HG will harm your baby if you have the right treatment. However, if it causes you to lose weight during pregnancy, your baby may be born smaller than expected (have a low birthweight).

Hyperemesis gravidarum and mental health

Having severe sickness can be exhausting and hard to cope with. You may feel lonely and worried about how long it will last. You may experience more serious issues such as anxiety and depression, or find it harder to manage existing mental health problems.

If you usually take mental health medication, you may not be able to keep these down. If so, talk to your doctor about other ways to take this medication.

Talk to your midwife or doctor if you are struggling to cope with your symptoms and/or your feelings. They can help you find more support. Many women and birthing people have mental health difficulties during pregnancy, even without managing severe sickness.

Many women and birthing people who suffer from HG experience have thoughts about suicide. For many people these are occasional or abstract thoughts, a feeling you just can’t cope with how things are right now and need something to change. For others it can be thinking about methods or making concrete plans. Mind has more information on coping with suicidal feelings. If you need to speak to someone urgently you can call the Samaritans on 116 123 or call 999, or text ‘SHOUT’ to 85258 to contact the Shout Crisis text line. There is support out there. If your doctor is not sympathetic and supportive, seek a second opinion. 

You might find it helpful to look for expert or peer support from Pregnancy Sickness Support. Their supporters have been there and understand what you are going through. They can give you information to help you get the care and treatment you deserve. They also offer counselling.

The HER foundation has lots of support groups on Facebook for people suffering from HG and those supporting them.

Hyperemesis gravidarum and work

You may not be able to work if you have hyperemesis gravidarum.  

You may decide to tell your employer about your pregnancy earlier than planned because your symptoms may be too difficult to hide or you need to take days off. Although this may not have been when you wanted to share the news, it does mean that your employer can help you.  

Once they know you are pregnant these days are recorded separately to normal sick days.  

All employers must do a risk assessment with you to see if your job has any risks to you or your baby. If there are any risks, they must make reasonable adjustments (do everything they can) to remove them.  

This can include giving you the time off you need, changing your work hours or, for example, making sure you are close to the toilet area.

Once your employer knows you’re pregnant, you’re protected against unfavourable treatment because of pregnancy-related discrimination. Your employer must record any pregnancy-related sickness separately so that it isn’t used against you in any disciplinary, redundancy or dismissal decisions.

Find out more about pregnancy and work.