About a half to two thirds of all pregnant women experience morning sickness. Not only is it nothing to be worried about, it can actually be protective.

Some women, however, suffer from extreme and relentless nausea and vomiting throughout their pregnancy, a condition known as hyperemesis gravidarum. Now scientists have not only discovered the exact cause of this condition that affects roughly two percent of pregnant people, but their finding is likely to lead to an effective treatment in the near future.

It is the mother's sensitivity to GDF15 that determines the intensity of her reaction to the hormone and the likelihood of experiencing hyperemesis gravidarum.

For most women who experience nausea and vomiting as part of their pregnancy, it typically happens during the first three months — the first trimester. But women with hyperemesis gravidarum have symptoms until they deliver. Severe cases can lead to weight loss, dehydration and hospitalization.

A connection between the hormone GDF15 and morning sickness had been identified in previous research, but researchers from the University of Southern California and the University of Cambridge in the United Kingdom, concluded it is the mother's sensitivity to GDF15 that determines the intensity of her reaction to the hormone and the likelihood of experiencing hyperemesis gravidarum.

“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,” Marlena Fejzo, a clinical assistant professor of population and public health sciences in the Center for Genetic Epidemiology at the USC's Keck School of Medicine and the paper's first author, said in a press release.

There may be two avenues for treatment based on this new research, according to the scientists. One would be to lower the level of GDF15, and the other would be to expose the individual to GDF15 before pregnancy. This could “tame” the sensitivity to the hormone by preparing the body ahead of the pregnancy.

Either treatment would work, they believe. “This study provides strong evidence that one or both of those methods will be effective in preventing or treating hyperemesis gravidarum, or severe morning sickness,” Fejzo said.

There are ways to treat, and even prevent milder forms of forms of morning sickness, according to the March of Dimes, an organization that works to improve the health of mothers and babies. It suggests:

  • Take a prenatal vitamin before you get pregnant. Talk to your health care provider about which one to take. Sometimes vitamins can upset your stomach, so take it with a snack.
  • Keep snacks by your bed. Eat a few crackers before you get up in the morning to help settle your stomach.
  • Eat 5 or 6 small meals each day instead of 3 larger meals.
  • Choose foods that are low in fat and easy to digest, like cereal, rice and bananas. Don't eat spicy or fatty foods.
  • Eat healthy snacks between meals. This can help keep your stomach from being empty and helps prevent nausea. Try snacks that are high in protein, like milk or yogurt.
  • Drink plenty of fluids, especially water.
  • Avoid smells that upset your stomach.

If your morning sickness is extreme or continues beyond your first trimester, talk to your obstetrician about it.

The study is published in Nature.