Nausea and vomiting during pregnancy could be due to a hormone produced by the foetus, according to a study involving scientists from the University of Cambridge and researchers from Scotland, the USA and Sri Lanka.
The study’s findings, published in 'Nature' magazine, could pave the way for new treatments.
In as many as seven out of ten pregnancies, women experience nausea and vomiting, commonly known as 'morning sickness.' For some – 1% to 3% of pregnancies – these symptoms can be severe. This severe condition is known as hyperemesis gravidarum, the most common cause of hospital admissions during the first three months of pregnancy.
The research suggests that morning sickness is caused by a hormone known as GDF15, produced by the foetus.
Varying genetic risk of severe morning sickness
Analysis of data from several studies of pregnant women, together with a combination of other approaches, including blood hormone measurements, cell studies and mice studies, led researchers to this conclusion.
They found that the severity of the nausea and vomiting correlates directly with the amount of GDF15 produced in the foetal part of the placenta and sent into the mother’s bloodstream. It is also related to the woman’s sensitivity to the effects of this hormone.
The team discovered that some women have a much higher genetic risk of hyperemesis gravidarum, linked to lower hormone levels in the blood and tissues outside of pregnancy.
Hereditary blood disorder protects against the condition
Similarly, women with a hereditary blood disorder called beta-thalassemia, which gives them naturally high GDF15 levels before pregnancy, experience little or no nausea or vomiting.
"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'll become so sick they require treatment and even hospitalization," said Professor Sir Stephen O'Rahilly, Co-Director of the Wellcome-Medical Research Council Institute of Metabolic Science at the University of Cambridge, who led the collaboration.
"We now know why: 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 be," he added. "Knowing this gives us a clue as to how we might prevent this from happening.
A key to effective treatment?
"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."
Co-author Dr Marlena Fejzo, from the University of Southern California, whose team had previously identified the genetic link between GDF15 and hyperemesis gravidarum, had personally suffered from the condition.
“When I was pregnant, I could hardly move without being sick,” she said. “I hope that now we understand the cause, we are moving closer to developing effective treatments.”
