Genes, Pregnancy, and Severe Nausea: What Science Reveals About Hyperemesis Gravidarum
For decades, millions of women have been told that severe nausea during pregnancy is “normal.” Today, science is beginning to challenge that assumption. A new study identifies clear biological causes behind the most extreme cases, offering answers to a condition that has long been overlooked.
The research, led by experts at the Keck School of Medicine of USC and published in Nature Genetics, analyzed genetic data from nearly 11,000 women with hyperemesis gravidarum and more than 460,000 controls from diverse populations, including Latina women. The findings point to a complex and clearly biological origin.
Hyperemesis gravidarum affects about 1 in 50 pregnancies. It is not a minor discomfort. The condition can lead to dehydration, severe weight loss, and hospitalization, posing risks to both mother and baby.
“We are uncovering fundamental aspects that were previously invisible,” said Marlena Fejzo, a researcher at USC’s Center for Genetic Epidemiology and a leading expert in the field. Her work has helped shift how the condition is understood in medicine.
The study identified ten genes associated with the disorder. Four had already been linked to pregnancy, including GDF15 and PGR, which are involved in placental development and hormonal regulation. But six newly identified genes now emerge as key contributors: FSHB, TCF7L2, SLITRK1, SYN3, IGSF11, and CDH9.
One of the most significant findings involves the gene TCF7L2, previously known for its role in type 2 diabetes. Its presence in this study suggests a link between metabolism, insulin regulation, and severe nausea during pregnancy. Researchers say its exact role is not yet fully understood, but it opens new directions for investigation.
The team used a genome-wide association study, or GWAS, to compare thousands of genetic profiles and identify patterns. This method is widely considered a gold standard in biomedical research by institutions such as the National Institutes of Health.
A central focus remains the hormone GDF15. According to Fejzo, the key factor is not just the hormone itself, but how sensitive each woman is to it. Those with lower levels before pregnancy may face a higher risk of severe symptoms, while higher levels may offer some protection.
This finding is reshaping clinical understanding. For years, many patients reported that their symptoms were dismissed or attributed to psychological causes. Now, scientific evidence confirms a measurable biological basis.
The study also suggests the brain may play an active role. Some women develop strong, persistent aversions to certain foods, making it even more difficult to maintain proper nutrition during pregnancy. These responses may be linked to neurological pathways associated with nausea and discomfort.
For Latino communities, where access to prenatal care can vary, these findings carry real implications. Identifying risk factors early could lead to faster intervention and help prevent serious complications.
There is still no definitive cure, but researchers say these genetic discoveries could become targets for future treatments. The next step will be translating these findings into clinical tools for early diagnosis and more effective care.
Science is beginning to offer something many women have long needed: validation, explanation, and, ultimately, the possibility of better solutions.