Researchers have finally discovered the cause of morning sickness in pregnancy—and may be close to a cure

GDF15—a hormone that exists throughout the body in low levels, but is produced in the placenta at higher levels during pregnancy—is indeed the cause of morning sickness, a new study out of the University of Southern California and University of Cambridge, published Wednesday, confirmed. 

Not every woman reacts strongly to the hormone—and that’s why some escape relatively unscathed (around 20%), while the most severe cases (called “HG,” hyperemesis gravidarum—around 2%) require hospitalization.

Researchers are looking at a couple of ways to tackle the problem: lowering the level of hormone in pregnant women (the study presents the first human evidence that doing so is likely safe), and exposing women to the hormone prior to pregnancy, to prepare for elevated levels later on.

“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 USC, and the paper’s first author—said in a news release about the study.

Genetic causes of morning sickness

Researchers uncovered specific reasons why some pregnant women might not develop HG or even mild morning sickness. One of them: Patients with genetic disease beta thalassemia—an inherited blood disorder—are largely immune from the phenomenon because their levels of GDF15 are chronically elevated.

Another: If a woman inherited a rare genetic mutation that causes chronically low levels of GDF15 throughout her body, but her baby does not, she’ll be exposed to more hormone than she’s used to, likely causing morning sickness. But if her baby also develops the mutation, she probably won’t develop the condition.

“For the first time, this interaction between mother and fetus helps explain why some women get HG during some—but not all—of their pregnancies,” Fejzo said, emphasizing that additional research is needed to confirm the findings.

Treatments for morning sickness in the works

Fejzo’s team hopes to investigate if metformin—an oral diabetes drug that increases GDF15 levels—can be used prior to potential pregnancy in women who have a history of HG, to prepare them for the upcoming hormone surge.

They’re also hoping to test an additional class of drugs already in clinical trials for cachexia—a metabolic condition that causes extreme weight loss—and nausea and vomiting in cancer patients. The drugs block GDF15 from binding to its receptor in the brain.

The research holds extra meaning for Fejzo, who suffered from HG during pregnancy.

Said Fejzo: “Hopefully, now that we understand the main cause of HG, we’re a step closer to developing effective treatments to stop other mothers from going through what I—and many other women—have experienced.”