Scientists have discovered why some women, including the Princess of Wales, suffer from severe nausea and vomiting during pregnancy.
Mother-of-three Kate has been plagued by hyperemesis gravidarum, which is thought to affect up to three percent of pregnancies.
The condition even led to her first pregnancy, with Prince George, being announced earlier than usual after she received hospital treatment.
The cause of such debilitating symptoms was previously unknown. But research has now identified a hormone, GDF15, produced by the foetus which may be responsible – offering hope of treatments.
A study led by Cambridge University found that how sick a mum-to-be felt depended on how much hormone was produced and how much the woman had been exposed to it before falling pregnant.
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Professor Sir Stephen O’Rahilly, director of the university’s Medical Research Council Metabolic Diseases Unit, explained: “The baby growing in the womb is producing a hormone at levels the mother is not used to.
“The more sensitive she is to this hormone, the sicker she will become. Knowing this gives us a clue as to how we might prevent this from happening.
“It also makes us more confident that preventing GDF15 from accessing its highly specific receptor in the mother’s brain will ultimately form the basis for an effective and safe way of treating this disorder.”
Women who had naturally low levels of GDF15 in their blood were more likely to suffer with hyperemesis gravidarum, the research found.
The findings suggest that at-risk women, including those genetically predisposed, could be gradually exposed to the hormone to build up tolerance before pregnancy. Tests in mice supported this theory.
The study, published in the journal Nature, also involved researchers in Scotland, the USA and Sri Lanka.
Dr Marlena Fejzo from the University of Southern California, has suffered with the condition herself.
She said: “When I was pregnant, I became so ill that I could barely move without being sick. When I tried to find out why, I realised how little was known about my condition, despite pregnancy nausea being very common.
“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.”
‘I was close to terminating my pregnancy’
Charlotte Howden suffered from symptoms so severe she considered terminating her pregnancy. The 40-year-old was sick up to 30 times a day and unable to keep food or fluids down.
Even swallowing her own saliva would make her sick – and excessive saliva production is another symptom of hyperemesis gravidarum.
Charlotte, now mum to seven-year-old Henry, said her GP advised her to try ginger, and, later, medication which left her feeling “comatose”. She was repeatedly admitted to hospital after becoming dangerously dehydrated.
Charlotte said: “When I went in again for my third time, I begged [the consultant] to help me because I was very close to making the decision to terminate.” The consultant prescribed her a new medication which finally overcame her sickness.
Charlotte, of Winchester in Hampshire, is now the CEO of Pregnancy Sickness Support, a charity that fights for better care and raises awareness of the condition.
She added: “When you are suffering from a condition and no one can tell you why, you start to think, oh, is it me? Is it something I’ve done?
“I’m so grateful for the dedication of the researchers, because this isn’t a condition that really ever made the headlines until the now Princess of Wales suffered with it.
“It wasn’t an area of research that people were really interested in. It was just morning sickness – why should we care?”