Her Doctor Said Her Illness Was All in Her Head. This Scientist Was Determined to Find the Truth.

Hyperemesis hospitalizations are thought to cost patients and insurers about $3 billion per year, she said, and then there are the expenses of medications, home health care, lost work and complications like postpartum depression. “The costs of it are just astronomical,” she said.

‘This is it’

Without funding to analyze the saliva samples accumulating in the lab freezer, Dr. Fejzo discovered an alternative strategy when her older brother gave her a 23andMe DNA testing kit for her 42nd birthday.

After registering her kit, she received a standard email giving her the option of participating in the company’s research studies by completing an online survey and consenting to the use of her genetic data.

“I saw what they were doing, which I thought was brilliant,” she said.

She asked 23andMe if they would include a few questions about nausea and vomiting in pregnancy on their customer survey, and they agreed. A few years later, she worked with the company to scan the genetic data of tens of thousands of consenting 23andMe customers, looking for variations in their DNA associated with the severity of nausea and vomiting during pregnancy. The results were published in the journal Nature Communications in 2018.

A handful of gene mutations were flagged as significantly different, but the most striking was for one that makes a protein called growth differentiation factor 15, or GDF15. Dr. Fejzo had never heard of it, but as soon as she started reading about it, “I was like, ‘Oh my God, this is it,’” she recalled.

GDF15 acts in a part of the brainstem that suppresses appetite and sets off vomiting, and it had already been shown to cause appetite and weight loss in cancer patients. Blood levels of the protein are naturally increased in pregnancy and have since been found to be even higher in those with severe nausea and vomiting.

Researchers speculate that GDF15 may have evolved to help pregnant women detect and avoid unsafe foods that might harm fetal development early in gestation. But in hyperemesis, this normally protective mechanism seems to run in overdrive, at least in part because of too much GDF15, said Stephen O’Rahilly, director of the metabolic diseases unit at the University of Cambridge, who now collaborates with Dr. Fejzo on GDF15 research.