UCLA Logo Annually, almost 60,000 expecting mothers are hospitalized possibly because of hyperemesis gravidarum (HG). Known as an extreme form of nausea and vomiting, HG is probably life-threatening and leads to pregnancy termination. Investigators from UCLA and the University of Southern California assert that women going through extreme morning sickness during pregnancy face increased risk of HG.

While conducting the study, scientists probed through the maternal and paternal family histories of women with HG and concluded that the condition could be genetic. Those with HG supposedly have a more than 17-fold risk of experiencing the debilitating condition. Through the course of the study, 650 HG patients treated with IV fluids were enrolled and asked to recruit, as a control, a friend who had at least two pregnancies lasting more than 27 weeks and who did not have HG. Authors then compared the family histories of extreme nausea in the women with HG to the controls.

“Pregnant women with a family history of extreme nausea in pregnancy should be aware that they may have it too, and health care providers should take a family history of nausea in pregnancy at the first visit with an obstetrician. The high familial prevalence strongly suggests a genetic component to this condition,” alleged Marlena Fejzo, an assistant professor of hematology–oncology at the David Geffen School of Medicine at UCLA and an assistant professor of maternal and fetal medicine at Keck School of Medicine of USC and the lead author.

It was noted that 207 women with HG and 110 controls had at least one sister who had been pregnant. HG women were apparently more than five times as likely as the controls to have a sister with severe morning sickness or HG. On encompassing sisters experiencing HG and excluding sisters with just severe morning sickness, HG participants were probably 17.3 times at odds of facing the condition. Reportedly 33 percent women with HG and 8 percent controls had an affected mother.

Scientists comment, “Because the incidence of hyperemesis gravidarum is most commonly reported to be 0.5 percent in the population, and the sisters of cases have as much as an 18-fold increased familial risk for HG compared to controls, this study provides strong evidence for a genetic component to extreme nausea and vomiting in pregnancy.”

Data on grandmothers’ pregnancies indicated that 18 percent with HG had a maternal grandmother with the condition and 23 percent had a paternal grandmother affected by it. So, the ailment probably passes on through the women’s fathers. However, the study findings seem to be limited by factors like usage of Internet in order to survey the volunteers and family histories were based on self-reports, which can lead to misclassification.

The study was published online in the American Journal of Obstetrics and Gynecology.