Scientists Pinpoint Cause of Morning Sickness To Hormone Made By Fetus

Scientists have pinpointed the cause of nausea and vomiting in pregnancy, "finding that the severity of illness is influenced by how much of a hormone called GDF15 the growing fetus makes," reports Science Magazine. The findings have been published in the journal Nature. From the report: GDF15 is present in the blood of nonpregnant people and is known to be associated with nausea; it's also been tested as a weight loss aid because of its tendency to suppress appetite. Levels of the hormone rise sharply in early pregnancy and increase throughout gestation. Pregnant people with higher GDF15 concentrations have been documented as having a higher risk of vomiting and nausea. Some researchers suggest the hormone-caused aversion to some smells and tastes might encourage an expectant parent to avoid foods potentially dangerous to the fetus. To find out more about GDF15 changes during pregnancy, University of Cambridge physician-scientist Stephen O'Rahilly and colleagues studied half a dozen pregnant people who were known from previous genetic screening to produce a slightly different version of the GDF15 protein from their fetuses. Researchers could take advantage of that difference to trace whether GDF15 in the parent's blood originated in the parental or fetal genome: Almost all of it came from the fetus, O'Rahilly says. The team also took a closer look at the link between GDF15 levels and pregnancy sickness. Consistent with previous research, questionnaires from more than 300 participants showed that people who reported vomiting and nausea had significantly higher levels of circulating GDF15 on average than people without these symptoms. The researchers also found elevated levels of GDF15 in an analysis of more than 50 women hospitalized with hyperemesis gravidarum. Still, hormone levels alone couldn't explain the difference in sickness severity. "There was a big overlap" in GDF15 levels between the groups, O'Rahilly says. He and co-author Marlena Fejzo, a researcher at the University of Southern California, suspected that people's sensitivity to GDF15 might also play a role. (Fejzo began to study the condition after her own pregnancy loss following hyperemesis gravidarum.) To test the idea, the researchers studied 10 nonpregnant people with a rare genetic variant known to carry a heightened risk of hyperemesis gravidarum. These people had reduced GDF15 levels in their blood, hinting that naturally low levels of the hormone might predispose someone to sickness during pregnancy. The researchers found the opposite when they asked 20 pregnant people with beta thalassemia, a blood disorder associated with high GDF15 levels, about their pregnancy symptoms: Just 5% of this group reported nausea or vomiting. O'Rahilly's lab found a similar pattern in animal experiments.

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