What is hyperemesis gravidarum, the rare, debilitating pregnancy condition?

While pregnancy is an exciting time for many keen mums-to-be, it can also take a huge toll on the body and be difficult to get through - especially if you suffer from extreme morning sickness.

Morning sickness is a common symptom of pregnancy, affecting around 70% of pregnant women. Although it is dubbed "morning" sickness, many women experience nausea at any time of the day.

But a more rare form of pregnancy-related nausea, known as hyperemesis gravidarum (HG), is believed to affect between 1-3% of women. The debilitating condition can sometimes result in hospitalisation.

Recently, researchers discovered the reason why some suffer worse than others. It is hoped that more effective treatments for pregnant women suffering from HG) could soon be introduced.

Academics from the UK, US and Sri Lanka said the condition is caused by exposure to the hormone GDF15 being produced by babies in the womb, with the severity of illness resting on how sensitive the mother is to the hormone.

To better understand the condition, the team analysed data from women recruited to various studies and found the level of nausea experienced by women in pregnancy related to the amount of GDF15 produced by the foetal part of the placenta.

The level of sickness also rested on how much of the hormone the woman had been exposed to prior to pregnancy.

The findings, published in Nature, could help find better treatments for HG, according to co-author Dr Marlena Fejzo, of the department of population and public health sciences at the University of Southern California.

"Hopefully, now that we understand the cause of hyperemesis gravidarum, we're a step closer to developing effective treatments to stop other mothers going through what I and many other women have experienced," she explains.

What is hyperemesis gravidarum?

Sickness is common during the first trimester or first half of pregnancy, and happens to around 80% of pregnant women.

However, only 1-3% of women experience excessive nausea and vomiting that can see them be sick multiple times a day. The condition is so extreme, sufferers are often unable to keep food or drink down.

A previous survey of 5,000 pregnant women with HG by the BBC, charity Pregnancy Sickness Support and researchers at King's College London found that 52.1% of women surveyed said they considered terminating their pregnancy due to HG. Some 4.9% said they did terminate a wanted pregnancy because of the severity of HG.

It also found that 25.5% of the women surveyed occasionally thought about suicide, while 6.6% of women regularly considered it. But help is out there.

Hyperemesis gravidarum symptoms

The main symptom of HG is prolonged and severe nausea and vomiting. Other symptoms can include dehydration due to lack of fluid and weight loss due to lack of food.

The NHS says that, unlike regular pregnancy sickness, HG doesn’t necessarily improve by 16 to 20 weeks and may even last the entire pregnancy.

Hyperemesis gravidarum causes

While the cause of HG are now starting to be uncovered, the NHS says there is some evidence that links it to the hormonal changes in a woman’s body that occur during pregnancy.

The health service also says that it can be hereditary, and you are more likely to get it if your mother has had it.

Treatment for hyperemesis gravidarum

The NHS recommends some medicines that are safe to use in the first trimester of pregnancy that can help improve symptoms of HG, including anti-sickness drugs, steroids, or a combination of both. It's important to visit your GP first so that they can recommend the right medication for you.

"HG can make you feel very unwell, but it's unlikely to harm your baby if treated effectively," the NHS points out. "However, if it causes you to lose weight during pregnancy, there is an increased risk that your baby may be born smaller than expected (have a low birthweight)."

The Princess of Wales famously suffered from HG in the early stages of each of her three pregnancies. In 2020 she revealed that she used hypnobirthing techniques, mindfulness and meditation to help her cope with it.

"I saw the power of it really, the meditation and the deep breathing and things like that, that they teach you in hypnobirthing, when I was really sick, and actually I realised that this was something I could take control of, I suppose, during labour. It was hugely powerful," Kate told the Happy Mum, Happy Baby podcast.

Experiencing hyperemesis

Louise Cooper, 26, was diagnosed with hyperemesis gravidarum (HG) when she became pregnant for the first time in April 2017.

The condition caused her to vomit so frequently that her teeth started falling out and six months after her first child, Zachary, now six, was born in November 2017, she had to have all of her remaining teeth removed because they were so damaged.

Cooper has since had two more children and suffered from HG each time. Despite the harrowing experience, she has embraced life without teeth, often going out without her dentures.

"The damage was caused by the acid from vomiting," Cooper explains. "I lost my first tooth at around 16 weeks' pregnant. It was just out of nowhere. I was told that my teeth would need to be removed as they were so damaged.

"It was very traumatic, I wouldn't wish it upon my worst enemy. It is unpleasant. It is emotionally and physically draining."

It's important to note that while HG is undeniably very difficult, this is an example of a more extreme case.

Where to get help for hyperemesis gravidarum

The charity Pregnancy Sickness Support is a brilliant resource for those struggling with the condition – as well as their partners.

You can call the charity's helpline for advice and support on 024 7638 2020, as well as visit their website.

If you're unable to talk, as many women with HG are, you can WhatsApp the team.

If you are struggling, also let your GP know who can offer help or, if you can, call the Samaritans any time any day on 116 123 for a non-judgemental voice to listen at the end of the phone.

You are not alone.

Extreme morning sickness: Read more

• Greg Rutherford's pregnant fiancée Susie Verrill shares gruelling reality of hyperemesis gravidarum (Yahoo Life UK, 5-min read)

• Pregnant women may be driven to abortions by extreme morning sickness, new survey reveals (Yahoo Life UK, 5-min read)

• Hyperemesis gravidarum isn't merely morning sickness - it's much more serious than that (Yahoo Life UK)

• Scientists think they've found the cause of morning sickness (Yahoo News UK, 2-min read)

Watch: Mum dropped two dress sizes while pregnant due to extreme morning sickness which saw her vomit up to 30 times a day

Additional reporting PA and SWNS.