By Emma Wilkinson
Health reporter, BBC News
Severe morning sickness occurs in up to two in a hundred pregnancies
Pregnant women are three times more likely to suffer from severe morning sickness if their mothers did, say Norwegian researchers.
Around 2% of women suffer excessive nausea and vomiting in pregnancy - known as hyperemesis gravidarum - which can require hospital treatment.
But a study of 2.3 million births showed a threefold higher rate in those whose mothers had had the condition.
Experts said the results could help women better understand their risk.
Hyperemesis is defined as excessive sickness which starts before the 22nd week of pregnancy and in its most serious form it can lead to dehydration and weight loss because women cannot keep food or water down.
It is the most common cause of admission to hospital in early pregnancy and can be a cause of low birth weight and premature birth.
The researchers said that previous studies have attributed the condition to "psychological causes".
They analysed birth records, which included information on pregnancy complications, from 1967 to 2006.
It found the daughters of women who had the condition during their pregnancy had a 3% risk compared with 1% in those whose mothers did not have it.
But there was no increased risk to the female partners of sons whose mothers had suffered from the illness.
The researchers said although the results suggest a genetic link between mothers and daughters, it is also possible that there are lifestyle or environmental factors shared between mother and daughter that increase the risk.
Writing in the British Medical Journal, they said the study "shed a new light" on the causes of hyperemesis in pregnancy.
"It might lead to a better appreciation of the underlying biology," they added.
Dr Catherine Nelson-Piercy, a consultant obstetric physician at Guy's and St Thomas' Foundation Trust in London, said that better understanding of the genetic risks of hyperemesis may help clinicians when counselling women about the risk of recurrence in future pregnancies.
She said many women were undertreated because of the legacy of thalidomide - a drug given for morning sickness in the 1960s which caused birth defects - despite the availability of safe drugs.
"It can be extremely debilitating, women can't work, can't look after their families and they need to be admitted to hospital.
"It is safe to take anti-sickness drugs and it's better for the baby and the pregnancy to treat this condition than let the woman get very severely ill and risk complications."
Patrick O'Brien, spokesman for the Royal College of Obstetrics and Gynaecology, said the study added to growing evidence that many conditions in pregnancy, such as diabetes or high blood pressure, were linked to a "genetic predisposition".