To celebrate Rare Disease Day, we’re sharing our research into rare diseases here at Guy’s and St Thomas’. We’ve also written about our work on the condition trimethylaminuria.

Here, Claire O’Neill speaks to Professor Catherine Williamson about her work on hyperemesis gravidarum.


Professor Catherine Williamson is a consultant obstetric physician at St Thomas’ Hospital and Professor of Women’s Health at King’s College London. She is a leading clinical researcher in maternal medicine in the UK and internationally.

Professor Williamson and her team carry out research into a number of rare diseases including intrahepatic cholestasis of pregnancy (ICP) and hyperemesis gravidarum (HG).

HG has had a large amount of media coverage in the last few years as the Duchess of Cambridge has suffered from the illness during all of her three pregnancies.

Professor Williamson explains: “Hyperemesis gravidarum is often referred to as severe morning sickness but it’s so much more than that. Around 7 in 10 pregnant women experience some vomiting or nausea (although not necessarily in the morning!) and this usually disappears by the 14th week. Women with HG, however, may vomit up to 50 times a day and for some this lasts for the entire pregnancy. This can then lead to dehydration, weight loss, low blood pressure when standing and ketosis, all of which can be extremely dangerous and even fatal in pregnancy.

“Around 1 in 100 women will be admitted to hospital as a result of HG. We don’t know very much about why some women get HG and others don’t, but we do know that HG has a strong genetic link and that women whose mothers had HG in pregnancy are three times more likely to develop the condition. Another study found that women with a sister who has had HG have a risk of around 1 in 5 of having it themselves.

“Our research is trying to find out which biomarkers may cause this illness. Biomarkers are are naturally occurring genes or proteins that appear in the blood, which can tell us what is happening in the body. So far only one study like this has been carried out about HG, and there is an urgent need to look at this in more depth and to find out more.

“We hope that by understanding more about this illness, we can work towards better treatment and outpatient care to make pregnancy much easier for women with HG.”

You can read more about HG on the NHS website

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