• Posted December 13, 2023

Scientists May Have Spotted the Cause, and Possible Prevention, of Morning Sickness

Sudden nausea and then a quick run to a nearby bathroom: Pregnant women know all too well the misery of morning sickness.

Now, British researchers believe they've pinpointed the root cause of the illness, and perhaps new ways to prevent it.

Morning sickness may have roots in a hormone produced by the fetus, called GDF15, which appears to act on the mother's brain to cause her to feel nauseous and vomit.

Exposing women to GDF15 before a pregnancy might build a tolerance, so that morning sickness is never an issue, an international team of researchers contend.

"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," noted study lead author Dr. Stephen O'Rahilly, of Cambridge University in the U.K.

"We now know why: the baby growing in the womb is producing a hormone at levels the mother is not used to," O'Rahilly said in a university news release.

He directs the Medical Research Council Metabolic Diseases Unit at Cambridge.

The more sensitive a woman might be to fetal GDF15, "the sicker she will become," O'Rahilly explained.

"Knowing this gives us a clue as to how we might prevent this from happening," he said. "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."

That's already been hinted at in mouse studies. In that research, mice exposed to high levels of GDF15 went off their food, suggesting they were feeling nauseous. However, that didn't happen for mice who'd been gradually exposed to the hormone beforehand and had built up a tolerance.

Study co-author Dr Marlena Fejzo, of the University of Southern California, came to this line of research with firsthand knowledge.

"When I was pregnant, I became so ill that I could barely move without being sick," she said in the Cambridge release. "When I tried to find out why, I realized how little was known about my condition, despite pregnancy nausea being very common." Fejzo is a researcher in USC's department of population and public health sciences.

In the new analysis, published Dec. 13 in the journal Nature, Fejzo, O'Rahilly and colleagues looked at data on pregnant women from a number of genetic and hormonal studies conducted in cells, mice and humans.

That research has helped firm up the notion that fetal GDF15 was driving hyperemesis gravidarum, the medical term for severe morning sickness.

They noted that the hormone is made, at very low levels, by all human tissues. But some women are more sensitive to fetal GDF15 than others.

Women with certain gene variants might be more sensitive to GDF15, bringing on more severe morning sickness, the researchers said.

On the other hand, women with the inherited blood disorder beta thalassemia are already exposed to high levels of GD515, naturally, and seldom experience morning sickness.

Charlotte Howden, who lives in the U.K., said her morning sickness got progressively worse, until she couldn't keep any food down and was sick as often as 30 times a day.

"When you are suffering from a condition and no one can tell you why, you start to think, 'Oh, is it me? Is it something I've done?'"she said in the Cambridge news release.

Hawdon said she's grateful for the new studies, "because it wasn't an area of research that people were really interested in. It was just morning sickness -- why should we care?"

More information

Find out more about morning sickness at the American College of Obstetricians and Gynecologists.

SOURCE: Cambridge University, news release, Dec. 13, 2023