Toronto, Dec 17 (IANS): The couples who immigrate to Canada are generally at lower risk of having a pre-term birth than Canadian-born couples, reveals a new study.

The findings reflect 'healthy immigrant effect' and suggests that people who emigrate tend to have better health outcomes than both Canadian-born couples and those who remain in their country of origin.

"Newcomers have a generally healthier lifestyle and experience less obesity than Canadian-born couples," said Joel Ray from Li Ka Shing Knowledge Institute, University of Toronto, Canada.

The rate of pre-term birth, which is defined as birth before 37 weeks of gestation, was on average three percent lower among immigrant couples to Canada than the rate of pre-term birth in their country of origin.

The study looked at more than 1.2 million births in Ontario and among parents from 184 countries, between 2002 and 2011.

The main causes of pre-term birth include spontaneous pre-term labour, premature rupture of membranes, and pre-eclampsia -- a condition characterized by high blood pressure and elevated protein in pregnant women.

Other research found that women from the Philippines, Ghana and Jamaica had some of the highest rates of pre-eclampsia, which is partly due to their higher rates of chronic hypertension.

"While most immigrants have lower rates compared to Canadian-born couples and those who stay in their home country, we know there are exceptional cases, where immigrant women are actually at higher risks," Ray noted.

"These women could stand to benefit from greater clinical screening and surveillance during pregnancy," Ray concluded.

The study was published online in the Journal of Obstetrics and Gynaecology Canada.