London (PTI): Pregnant women in India are three times more likely to suffer from extreme nausea and vomiting than their counterparts in many western countries, a new study has revealed.

Researchers at Norwegian Institute of Public Health have carried out the study and found that extreme nausea and vomiting vary among pregnant women in different countries, the 'Scandinavian Journal of Public Health' reported.

Earlier studies reported that 90 per cent of pregnant women experience some degree of nausea and vomiting, whereas 0.5 to 2 per cent have hyperemesis gravidarum.

"This is one of the largest studies carried out on hyperemesis gravidarum. In contrast to earlier studies we tested the quality of the data and therefore have confidence in our findings," lead researcher Ase Vikanes said.

In fact, the researchers came to the conclusion after analysing 900, 000 first-time pregnancies over a forty year period in Norway. Socio-demographic factors such as marital status, country of birth, education and age in each pregnancy were also studied.

Mothers born in India and Sri Lanka had the highest prevalence of hyperemesis gravidarum, followed by those born in Africa (excluding North Africa) and Pakistan by 3.2 per cent, 3.1 per cent and 2.1 per cent respectively.

The study also found that ethnic Norwegians, North Americans and Western Europeans had the lowest prevalence by 0.9 per cent, 0.9 per cent and 0.8 per cent, respectively. Maternal age between 20-24 years old, being married, carrying a female foetus or more than one foetus were all socio-demographic characteristics associated with a higher prevalence rate of hyperemesis gravidarum.

"The difference in prevalence of hyperemesis gravidarum related to the mother's country of birth cannot be explained by differences in socio-demographic characteristics.

"We have to look for other explanations such as genetic factors, a change of diet or a history of infections. This topic needs further research to identify ways to prevent this life-threatening and distressing condition," Vikanes was quoted by the 'ScienceDaily' as saying.