Researchers Say This Hormone is Behind Morning Sickness

A woman in blue sweater with her head in her hands.
Many pregnant people develop nausea or vomiting during pregnancy. Eclipse Images/Getty Images
  • A new study has found evidence for what causes morning sickness.
  • Researchers say a hormone produced by the fetus may be the reason some women develop nausea and vomiting during pregnancy.
  • In some cases, morning sickness can be severe, causing people to end up in the hospital.

Morning sickness, the common side effect of pregnancy most known as nausea and vomiting in the first trimester of pregnancy, is very likely caused by a single hormone.

The research was published this week in a study led by researchers at the University of Cambridge in the journal Nature.

The discovery offers some potential for developing a more effective way to treat morning sickness, especially severe cases, although there’s no immediate clear path to pharmaceutical applications.

Researchers said that the hormone, a protein called GDF15 that is produced by the fetus, can cause the nausea and vomiting which affects seven out 10 pregnancies. They found the level of sickness was directly related to how much of the hormone a woman had been exposed to before pregnancy as well as how much of the hormone the fetus produces.

A limited amount of exposure before pregnancy can lead to more severe first-trimester sickness known as hyperemesis gravidarum, which can send some women to the hospital with dehydration and, in extreme cases, leads to death.

The research suggests that by creating more opportunities for exposure to GDF15 before pregnancy, a woman’s resilience to it will increase, and the severity of morning sickness can be reduced.

What is the hormone linked morning sickness?

The study notes that GDF15 is produced at low levels in all tissues outside of pregnancy. However, a high level of GDF15 in the placenta appears to be a feature of certain species, including primates, as an evolutionary feature that can signal to the mother’s brain in early pregnancy that certain foods have a higher risk of containing infectious organisms.

Many pregnant people report some aversion to certain foods or beverages during pregnancy.

But, the study authors cautioned that “there is considerable overlap between symptomatic and asymptomatic women, so GDF15 levels alone cannot be responsible for determining who is and who is not affected.” And some professionals pointed out that more research needs to be done since the study suggests a direct cause, not stating it.

Dr. Kecia Gaither,  double board certified in OB/GYN and Maternal Fetal Medicine, Director of Perinatal Services/Maternal Fetal Medicine at NYC Health + Hospitals/Lincoln in the Bronx, told Healthline that implementing these findings into a treatment will take time and that the study is a “suggested possible” cause for morning sickness.

“I’m sure there are more studies and research needed to address manufacture of dose, preparation, pharmacokinetics, etc, of this particular hormone,” Gaither said. “Results and an ultimate product for distribution might take years to come to fruition.”

How does this hormone affect pregnant women?

The Cambridge researchers suggest in the study that the intensity of morning sickness can be tied to the sensitivity of a pregnant woman to the hormone.

Lower levels of GDF15 in the blood and tissues before pregnancy are tied to a rare genetic variant that can increase a woman’s risk of hyperemesis gravidarum. But in a complicated inverse dynamic, women who have the blood disorder beta thalassemia can have very high levels of GDF15 before getting pregnant, and during pregnancy they tend to experience almost no nausea or vomiting.

“If the mother has never been exposed to the hormone, she has a severe reaction as opposed to someone who has been exposed,” Gaither said. “Proposed ‘treatment’ reflects exposing the woman in the nonpregnant state to the hormone, so she becomes sensitized to the hormone, and thus has no development of hyperemesis gravidarum once she becomes pregnant.”

What treatments are available to women experiencing morning sickness?

Dr. Patricia Faraz, board certified OB/GYN at The Women’s Hospital at MemorialCare Saddleback Medical Center in Laguna Hills, California, told Healthline that while there are some pharmaceutical combinations to treat morning sickness, it’s still difficult to fully neutralize the extreme symptoms of hyperemesis gravidarum.

Vitamin B6, in combination with antihistamines, can work well for moderate forms of nausea and vomiting in pregnancy, and the anti-nausea medication Zofran was a consistent solution for many years until it became associated with heart defects.

“Unfortunately, it is still used quite a bit because we don’t really have anything that’s that much better,” Faraz said. “There’s a whole series of drugs that like Reglan, promethazine, and these drugs all have a high risk of side effects. And most of the time they’re not well tolerated by the patient and cause drowsiness and some movement disorder-type side effects as well. They’re a little bit scary to use.”

May be just one cause of morning sickness

Historically, studies of pregnant women have been hindered by the delicate nature of the situation: Pregnant people are less inclined to do any sort of experimental treatments, and researchers are equally tentative. For many years, morning sickness was thought to be caused by other hormones, elevated levels of estrogen, H. pylori, or genetic factors.

Faraz also points out that the failure of Thalidomide, which was used in the 1950s and 1960s and linked to severe congenital disabilities, may also have made research into morning sickness more difficult.

“If we could have a medication that exactly targets what’s causing the nausea and vomiting, we’d all be so excited about that, because everything we have now is just kind of a band-aid,” Faraz said. “And the medications have a lot of side effects, and we always worry about prescribing them, but sometimes our patients are so miserable, we have to.”

Faraz also said that while the study offers some promise for treating these undesirable effects of early pregnancy, there are still many factors that contribute to morning sickness — just pushing a button on GDF15 is not a magic bullet.

“There’s some other things that highly contribute to pregnancies, and that’s the psychosocial side,” Dr. Faraz said. “In my experience, women who have more depression or an unwanted pregnancy tend to have a lot more symptoms. It’s not simple, like, ‘Oh, it’s just this receptor that we found that causes hyperemesis gravidarum’ — I think it’s a combination of things.”

Takeaway

A new study suggests that the hormone GDF15, which is produced by the fetus during pregnancy, could be a cause of morning sickness.

The study offers some hope for severe cases of morning sickness known as hyperemesis gravidarum, which affects less than 3% of pregnant women but can send them to the hospital with dehydration.

But more research needs to be done to establish a pharmaceutical application of the research, and studies on pregnant people are often complicated and slow to happen.

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