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Pregnant women who find themselves retching over the toilet and overcome with nausea may finally gain some insight into what's causing their extreme morning sickness. According to a new study, researchers have identified two genes that may increase the risk for this debilitating condition, which is known as hyperemesis gravidarum.

The genes associated with hyperemesis gravidarum, known as GDF15 and IGFBP7, are involved in the development of the placenta and also play a role in appetite regulation, said study lead researcher Marlena Fejzo, an obstetrics researcherat the University of California, Los Angeles and the University of Southern California.

"Having the DNA variation we identified [in these genes] does appear to increase risk for hyperemesis gravidarum, Fejzo told Live Science in an email. "However, the variation we found is common, so some women will carry the variation and not have hyperemesis gravidarum, and vice versa." [Conception Misconceptions: 7 Fertility Myths Debunked]

About 2 percent of pregnant women have hyperemesis gravidarum, including Catherine, the Duchess of Cambridge, whose condition was so bad during her pregnancy with the now 4-year-old Prince George that she had to be temporarily hospitalized, Live Science previously reported.

Catherine, Duchess of Cambridge, shown here at the annual Irish Guards St Patrick's Day Parade on March 17, has experienced "hyperemesis gravidarum" in past pregnancies. This condition that causes extreme morning sickness during pregnancy.
Catherine, Duchess of Cambridge, shown here at the annual Irish Guards St Patrick's Day Parade on March 17, has experienced "hyperemesis gravidarum" in past pregnancies. This condition that causes extreme morning sickness during pregnancy.
Credit: Max Mumby/Indigo/Getty

Hyperemesis gravidarum also plagued Fejzo in two of her pregnancies. It was so severe in her second pregnancy that she "could not move without vomiting and did not keep any food or water down for 10 weeks," she said. "I was put on a feeding tube, but ultimately lost the baby in the second trimester."

At that time, little was known about the causes of hyperemesis gravidarum, so Fejzo partnered with the Hyperemesis Education and Research (HER) Foundation and surveyed women about their family history of the condition. The results showed that if a woman experienced severe morning sickness, her sister had a 17-fold increased risk of having it, too — an indication that genes play a role in the condition, Fejzo said.

Realizing she was onto something, Fejzo did a comparative DNA study by collecting saliva samples from hyperemesis gravidarum patients as well as from pregnant women who didn't experience any nausea and vomiting. Then, she partnered with 23andMe, a commercial genomics company based in Mountain View, California, to do a genome scan and validation study, which showed that the genes GDF15 and IGFBP7 were linked to the condition, she said.

Moreover, in data that has yet to be published, Fejzo and her colleagues showed that the proteins associated with the two genes were abnormally high in the blood of patients hospitalized for hyperemesis gravidarum, compared with pregnant women with normal nausea and vomiting and pregnant women with no nausea and vomiting, according to research they presented at the International Colloquium on Hyperemesis Gravidarum in 2017.

Researchers already know a few things about the two genes that were identified in the study, Fejzo noted. For instance, both are known to play a role in cachexia, a condition with symptoms including loss of appetite and muscle wasting, symptoms that are also seen in hyperemesis gravidarum.

Given that cachexia kills 20 percent of cancer patients, several groups are doing research on mice to see how they can ultimately increase the appetites of individuals with this condition. "Therefore, I am very hopeful that our findings will lead to novel therapies to treat hyperemesis gravidarum, if they are safe in pregnancy," Fejzo said.

The study was published online today (March 21) in the journal Nature Communications.

Original article on Live Science.