Hyperemesis gravidarum (HG) does have a significant genetic component. Research has identified specific genes that increase a woman’s risk, and family studies show the condition runs strongly in families. If your mother had HG during pregnancy, your risk is roughly three times higher than average.
The Gene Behind Severe Pregnancy Nausea
The strongest genetic link to HG involves a gene called GDF15, which produces a hormone that acts directly on nausea receptors in the brainstem. During pregnancy, the placenta and fetus produce large amounts of this hormone, and it enters the mother’s bloodstream. The largest genome-wide association study of HG to date, covering more than 7,400 cases and nearly 360,000 controls, confirmed that variants in the GDF15 gene are the most significant genetic risk factor for the condition.
A second gene, IGFBP7, also plays a role. Both GDF15 and IGFBP7 are active during early placenta formation and influence appetite and feeding behavior. In animal models, the proteins these genes produce cause loss of appetite. Their dual roles in placenta development and appetite suppression may explain why HG has persisted through human evolution: the same genes that help establish a healthy pregnancy also happen to trigger severe nausea.
Notably, the study found no association between HG and genetic variants related to hCG, the pregnancy hormone long blamed for morning sickness. While hCG levels do rise alongside nausea symptoms, that correlation appears to be coincidental. When researchers looked at whether hCG levels actually predicted vomiting, the relationship fell apart. GDF15 levels, on the other hand, were consistently and significantly higher in women who experienced vomiting.
Why Sensitivity Matters as Much as the Hormone
The severity of HG isn’t just about how much GDF15 your body produces during pregnancy. It also depends on how sensitive you are to the hormone before you become pregnant. A 2023 study published in Nature found that both fetal production of GDF15 and the mother’s pre-existing sensitivity to it contribute substantially to HG risk. Women whose bodies are accustomed to higher baseline levels of the hormone seem to tolerate the pregnancy surge better.
This finding explains some otherwise puzzling patterns. Women with beta thalassemia, a blood disorder that chronically elevates GDF15 levels, report strikingly less nausea during pregnancy. Similarly, cigarette smoking before pregnancy, which also raises GDF15 levels, is associated with lower HG risk. The body appears to build a tolerance: if you’re already exposed to higher levels of the hormone, the sharp increase during early pregnancy doesn’t hit as hard.
This sensitivity component is itself partly genetic. Your genes influence your baseline GDF15 levels and how strongly your brainstem receptors respond to the hormone. So the genetic picture is layered: some gene variants increase the amount of hormone produced, while others affect how intensely your body reacts to it.
How Strongly HG Runs in Families
Family studies put concrete numbers on the hereditary pattern. Daughters born after a pregnancy complicated by HG have about a 3% chance of developing HG themselves, compared to 1.1% for daughters whose mothers had uncomplicated pregnancies. That translates to roughly a threefold increase in risk.
Even when the mother’s HG occurred in a different pregnancy (not the one that produced the daughter in question), the daughter’s risk was still elevated, with odds roughly three times higher than baseline. This pattern is important because it points to inherited genetic susceptibility rather than something specific to that particular pregnancy environment. The mother carries the gene variants regardless of which pregnancy triggers symptoms, and she can pass those variants to any of her daughters.
Other Genetic Leads
Beyond GDF15 and IGFBP7, the large meta-analysis identified a third confirmed genetic region near the progesterone receptor gene. Using a broader statistical threshold, researchers also found suggestive links to genes involved in motion sickness and chemotherapy-induced nausea, as well as a gene related to thyroid-stimulating hormone receptor activity. One of these candidates, SDK1, had previously been found mutated in a family with multiple HG cases.
These additional genes haven’t been confirmed as firmly as GDF15, but they paint a picture of HG as a condition influenced by multiple genetic pathways, not just one. Some of these pathways overlap with other nausea-related conditions, which may explain why women prone to motion sickness or migraine sometimes report worse pregnancy nausea.
Ethnic and Population Differences
There are measurable differences in pregnancy nausea rates across ethnic groups, which further supports a genetic contribution. In one study that controlled for income, age, and other confounding factors, Asian and Black women were significantly less likely to report first-trimester nausea and vomiting than Caucasian women. These differences disappeared in the second trimester and didn’t apply to the severity of symptoms, only to whether nausea occurred at all. The genetic variants that influence GDF15 levels and sensitivity vary in frequency across populations, which likely accounts for at least some of this variation.
What This Means for Treatment
Understanding the genetic mechanism has opened the door to more targeted approaches. Since GDF15 triggers nausea by binding to a specific receptor in the brainstem called GFRAL, researchers are developing drugs that block this interaction. These include antibodies that prevent GDF15 from reaching its receptor and smaller molecules that interfere with the signaling pathway. These treatments are still experimental and face particular challenges around safety during pregnancy, but they represent the first therapies designed to address the actual biological cause of HG rather than just suppressing symptoms.
The sensitivity finding also raises a prevention concept: if pre-pregnancy exposure to GDF15 builds tolerance, it may eventually be possible to gradually increase a woman’s GDF15 levels before conception to reduce symptom severity. This is speculative for now, but it follows directly from the genetic and biological evidence.
An Evolutionary Leftover
One question the genetic evidence helps answer is why HG exists at all. The genes involved in HG play essential roles in early placenta formation and in regulating appetite. In a world where pregnant animals face risks from contaminated or toxic food, a mechanism that suppresses appetite during the most vulnerable stage of fetal development could be protective. Recent reviews describe pregnancy nausea as a mechanism that likely provided an evolutionary advantage in the wild but is no longer necessary for human survival. The same genes that once kept early pregnancies viable by reducing food intake now, in some women, overshoot into a debilitating condition.