A new study has revealed that women whose sisters experienced extreme morning sickness, are 17 times more likely to develop the condition.
Hyperemesis gravidarum (HG) is an extreme form of nausea and vomiting that endangers their lives and often forces them to reluctantly terminate their pregnancies.
Researchers from UCLA and the University of Southern California traced both the maternal and paternal family histories of women with HG and found not only that the condition could be genetic but that women with sisters who had HG could have a more than 17-fold risk of experiencing the debilitating condition too.
"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," said lead author Marlena Fejzo of UCLA.
"The high familial prevalence strongly suggests a genetic component to this condition," added Fejzo.
Researchers surveyed about 650 participants for the joint study on the genetics and epidemiology of HG.
Women who had been diagnosed with HG and treated with IV fluids were asked to recruit, as a control, a friend who had at least two pregnancies lasting more than 27 weeks and who had not had HG.
The researchers then compared the family histories of extreme nausea in the women with HG with those of the controls. The researchers found that women with HG were more than five times as likely as the controls to report having a sister with severe morning sickness or HG.
When including sisters who had experienced HG - and excluding sisters with just severe morning sickness - study participants with HG had 17.3 times the odds of also having the condition.
In addition, 33 percent of the women with HG reported having an affected mother, compared with only 8 percent of the controls.
The findings were published online in the American Journal of Obstetrics and Gynaecology.