FILE - A pregnant woman feeling sick over a toilet. (Photo by Classen/ullstein bild via Getty Images)
A study by researchers from across the globe has identified the possible cause of nausea and vomiting for so many pregnant women, including those who suffer from an extreme form called hyperemesis gravidarum (HG).
The findings, published this week in the journal Nature, suggest the cause is a hormone produced by the fetus known as GDF15.
The research also points to a potential way to prevent pregnancy sickness by exposing mothers to GDF15 ahead of pregnancy.
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Morning sickness in pregnancy: How common is it?
As many as seven in 10 pregnancies are affected by nausea and vomiting, according to researchers at the University of Cambridge, who led the study.
Some women, thought to be between 1-3% of pregnancies, suffer from HG. The pregnancy sickness can be severe, and even life-threatening to the fetus and the mother. HG can also require IV fluids to prevent dangerous levels of dehydration.
Women such as Amy Schumer and Kate Middleton, the now-Princess of Wales, became so sick during pregnancy with HG that they needed to be admitted to the hospital.
Some therapies exist to help and are at least partially effective, but widespread ignorance of the disorder as well as fear of using medication during pregnancy have led to many women being inadequately treated, the researchers said.
And while morning sickness in pregnancy is quite common, little has been known about the cause.
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Growing body of evidence points to this hormone
A growing body of research has linked the symptoms of pregnancy sickness to GDF15, according to the study, which also included researchers from the United States and Sri Lanka.
GDF15 is a hormone produced in the placenta that increases substantially during pregnancy. The new study supports the causal role of GDF15 in morning sickness, and it suggests that a woman’s sensitivity to the hormone can determine the severity of her symptoms.
The team analyzed data from women recruited for a number of studies. They used a combination of approaches including human genetics, new ways of measuring hormones in pregnant women’s blood, and studies in cells and mice.
The researchers also found that women exposed to lower levels of GDF15 before getting pregnant experienced more severe symptoms.
"We now know that women get sick during pregnancy when they are exposed to higher levels of the hormone GDF15 than they are used to," Marlena Fejzo, PhD, a clinical assistant professor of population and public health sciences at the University of Southern California and the paper’s first author.
Women who are more sensitive to the hormone get the sickest, according to Professor Sir Stephen O’Rahilly, MD, co-director of the Wellcome-Medical Research Council Institute of Metabolic Science at the University of Cambridge, who led the collaboration.
"Knowing this gives us a clue as to how we might prevent this from happening," O’Rahilly said.
Possible ways to prevent pregnancy morning sickness
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Lowering the GDF15 hormone is one way to potentially address pregnancy sickness, according to the researchers. Another way to minimize symptoms involves exposing women to GDF15 before getting pregnant to "prime" them for elevated levels once they do become pregnant, according to the study.
"This study provides strong evidence that one or both of those methods will be effective in preventing or treating HG," Fejzo said.
The research team plans to determine whether priming women with GDF15 exposure prior to pregnancy can reduce their nausea and vomiting – and perhaps even prevent severe illness like HG.
Fejzo – who suffered from HG herself – hopes to test whether metformin, a drug that increases GDF15 levels, is safe for use in patients who have a history of HG.
The researchers are also seeking to test an additional class of drugs that may help with HG by blocking GDF15 from binding to its receptor in the brain. Several such drugs are already in clinical trials for cachexia, which is a complex metabolic condition that causes extreme weight loss, and for cancer patients with nausea and vomiting, according to the researchers.
Fejzo said the findings from the latest study offer hope for women who have experienced severe illness during pregnancy.
"Hopefully, now that we understand the main cause of HG, we’re a step closer to developing effective treatments to stop other mothers from going through what I, and many other women, have experienced," Fejzo said.
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This story was reported from Cincinnati.