Scientists have discovered why many women experience morning sickness during pregnancy, raising the prospect of a cure for the condition.
The study revealed that a hormone produced by the fetus is the trigger for nausea and vomiting during pregnancy, which in extreme cases may require hospital treatment. Most importantly, women who have naturally low levels of the hormone before pregnancy tend to be more sensitive to the surge of the hormone, called GDF15, in the first trimester, the research suggests.
“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,” says Marlena Fejzo, a clinical assistant professor of population and public health sciences at the University of Southern California. California’s Keck School. of Medicine, who is the paper’s first author.
Nausea and vomiting affect approximately 80% of women at some point during pregnancy. About 2% of women, including Catherine, the Princess of Wales, experience an extreme form of morning sickness called hyperemesis gravidarum (HG), which can lead to weight loss, dehydration and hospitalization. However, until now, the underlying cause of pregnancy sickness was unclear.
Although there are some partially effective therapies for pregnancy sickness, the lack of scientific understanding of the disease, compounded by a fear of using medication during pregnancy, means that many women are inadequately treated.
Charlotte Howden, the charity’s chief executive Pregnancy Disease Support, said her GP suggested trying ginger or “eating a little and often” when she sought help for HG, and she was subsequently hospitalized several times during her pregnancy.
“It’s just what we’re told to expect in early pregnancy,” she said. “When you suffer from a condition and no one can tell you why, you start thinking: is this something I did? I am so grateful for the dedication of the researchers as this is not a condition that really ever made the news until the now Princess of Wales suffered from it. It was not an area of research that people were really interested in.”
The latest research provides several lines of evidence linking these symptoms to GDF15. This suggests that lowering the hormone, or blocking its action, may prevent disease. Another approach could be to “prime” women by exposing them to the hormone before pregnancy.
“Most women who become pregnant will experience nausea and sickness at some point, and while this is not pleasant, for some women it can be much worse – they will become so ill that they require treatment and even hospitalisation,” says Prof Sir Stephen O. ‘Rahilly, a co-director of the Wellcome-Medical Research Council Institute of Metabolic Science at the University of Cambridge, who led the international collaboration behind the discovery.
“We now know why: the baby growing in the womb produces 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 an idea of how we can prevent this from happening.”
GDF15 is made at low levels in all tissues outside of pregnancy. However, women with a rare mutation in the gene that codes for GDF15 have unusually low levels of the hormone outside of pregnancy.
The study, published in Nature, shows that these women are at increased risk of HG during pregnancy, when they are suddenly exposed to high levels of GDF15. But if their fetus also carries the mutation, they are less likely to experience severe symptoms.
Similarly, patients with beta-thalassemia, an inherited blood disorder that causes chronically high levels of GDF15, are largely protected from pregnancy-related disease.
The research team also showed in mice that exposing mothers to low levels of GDF15 before pregnancy can help prevent pregnancy sickness.
The next step is to test whether women who have a history of HG with GDF15 before pregnancy can reduce nausea and vomiting or even prevent the symptoms.
