It's a symptom that pregnant women would be happy to do without and affects up to seven out of ten pregnancies: nausea and vomiting. But a major discovery could pave the way for treatments. According to the results of a study, published recently in the journal Nature, involving scientists from the University of Cambridge and researchers from Scotland, the United States and Sri Lanka, these ailments are due to a hormone produced by the fetus, a protein known as GDF15.
In some women, between one and three out of every 100 pregnancies, these symptoms can be severe. This is called hyperemesis gravidarum and is the most common cause of hospital admission in women during the first three months of pregnancy. Kate Middleton, Prince William's wife, suffered from it during her three pregnancies.
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To arrive at their result, the researchers studied data from women recruited in a number of studies and used a combination of approaches: measurements of hormones in the blood of pregnant women, studies on cells and mice... They showed that the degree of nausea and vomiting a woman experiences during pregnancy is directly related to both the amount of GDF15 produced by the fetal part of the placenta and sent into her bloodstream, and her sensitivity to the effect of this hormone.
Genetic Association
In particular, the team found that some women have a much higher genetic risk of hyperemesis gravidarum, which is associated with lower levels of the hormone in the blood and tissues outside of pregnancy. Similarly, women with an inherited blood disorder called beta-thalassemia, which allows them to have naturally very high levels of GDF15 before pregnancy, experience little or no nausea or vomiting.
"The baby that grows in the womb produces a hormone at levels that the mother is not used to. The more sensitive it is to this hormone, the sicker it will be," said Professor Stephen O'Rahilly, co-director of the Institute of Metabolic Sciences at the Wellcome-Medical Research Council at the University of Cambridge, one of the study's authors. "Knowing this gives us a clue as to how we might prevent this from happening," he continued.
Co-author Dr. Marlena Fejzo of the University of Southern California, whose team had previously identified the genetic association between GDF15 and hyperemesis gravidarum, had suffered from the condition herself: "When I was pregnant, I could barely move without being sick," she testified. "I hope that now that we understand the cause, we are one step closer to developing effective treatments."