Morning sickness during pregnancy has largely remained unexplained – until now

The majority of women experience morning sickness during pregnancy, but what causes nausea and vomiting while expecting has largely remained unexplained – until now.

A study published in the Nature journal Wednesday found that a hormone released by babies in the womb, a protein called GDF15, might be responsible for pregnancy sickness, including in its most severe form, called hyperemesis gravidarum (HG).

Researchers from the University of Cambridge, University of Southern California, University of Edinburgh and others said in their paper that fetal production of GDF15 and the mother’s sensitivity to it “contribute substantially” to the risk of HV.

“I think we really do now pretty much fully understand or have a very good understanding of why women get sick in pregnancy and in particular why some women get very sick in pregnancy,” said Sir Stephen O’Rahilly, a University of Cambridge professor and one of the study authors, in an interview with Global News Thursday.

O’Rahilly said the severity of pregnancy sickness is determined not only how much of the GDF15 hormone the fetus makes and puts into the mother’s bloodstream, but also how sensitive the mom is to that hormone.

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If women are exposed to this hormone before pregnancy that will likely make them even more sick when expecting, the study found. 

Morning sickness is a common condition that typically occurs in the first trimester or first three months of pregnancy. It can occur at any time of the day but tends to be worst in the morning. Hence the name.

Most women have mild symptoms including an upset stomach, nausea, loss of appetite and vomiting, but in its most severe form, HV could also require hospitalization.

Canadian fashion model Willow Allen, who is 34-weeks pregnant, has been suffering extreme nausea and vomiting throughout her pregnancy.

In an interview with Global News Thursday, the Inuk model said she has ended up in hospital multiple times to get IV fluids for dehydration.

“I think it’s really hard to explain to people just how severe the sickness really is and how debilitating it really is,” Allen, who is from the Northwest Territories, said.

Allen, who was featured in Vogue last month, said she lost 15 pounds at the beginning of her pregnancy and she had to take a lot of nausea medication to keep things down while trying to gain back that weight.

“I’ve never been in such a weak physical state before and just having such little control over your life essentially because of how limited you are and not being able to do really anything for yourself when it’s that severe – it was really scary. ”

Previous research into morning sickness has pointed to hormonal changes or low blood sugar as contributing factors.

This latest study pinpointing the hormone GDF15 “gives us a very clear idea of what we should do to treat and prevent” pregnancy sickness, O’Rahilly said.

“I think that gives us the next step to really being confident that if we manipulate this appropriately, we can help women with the more severe end certainly of the problem.”

One way to treat women suffering with HV would be to try to block the action of the GDF15 at the receptor in their brains, which would require creating an antibody, O’Rahilly said, adding “that’s relatively easy to do.”

“We need to make that antibody so it doesn’t cross the placenta and therefore we have the safety element of it not getting into the fetus,” he said.

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Another possibility is to give women this protein in the form of a drug, so it desensitizes them to their own GDF15.

Metformin is one of those drugs, which is widely used to treat Type 2 diabetes, which can increase your level of GDF15 by two to three-fold, O’Rahilly said.

Health Canada has authorized Diclectin as a safe treatment option for nausea and vomiting in pregnancy.

To relieve symptoms, the Society of Obstetricians and Gynaecologists of Canada recommends taking ginger, doing acupressure and substituting iron-containing prenatal vitamins with multivitamins with folic acid.

With this new research raising hope for another treatment and even possibly a cure going forward, Allen said it comes as “huge relief.”

“Honestly, hearing that there might be that just makes me so emotional,” she said.

— with files from Global News’ Abigail Bimman