Couples who immigrate to Canada are generally at lower risk of having a preterm birth than Canadian-born couples, new research has found.

The findings reflect the ‘healthy immigrant effect,’ which 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, according to the study published online today in the Journal of Obstetrics and Gynaecology Canada.

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

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

“Newcomers have a generally healthier lifestyle and experience less obesity than Canadian-born couples,” said Dr. Joel Ray, a physician at St. Michael’s Hospital and researcher in its Li Ka Shing Knowledge Institute. “They’re also at lower risk of preterm birth than couples who stay in their country of origin, which may be explained by the fact that we are selecting some of the healthiest immigrants to come to Canada.”

But there were exceptions to these findings, suggesting that the healthy immigrant effect doesn’t apply equally to all immigrant groups. The researchers found that the risk of preterm birth in Ontario was highest among couples who originated from Guyana, Congo, Trinidad and Tobago, Jamaica, Ghana and the Philippines.

Other research by Dr. Ray and colleagues at St. Michael’s 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.

Dr. Ray said that women originating from these countries who have elevated blood pressure in early pregnancy should be considered for low-dose Aspirin, which helps prevent preeclampsia.

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

“While most immigrants have lower rates of 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,” said Dr. Ray. “These women could stand to benefit from greater clinical screening and surveillance during pregnancy.”

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About St. Michael’s Hospital

St. Michael’s Hospital provides compassionate care to all who enter its doors. The hospital also provides outstanding medical education to future health care professionals in more than 23 academic disciplines. Critical care and trauma, heart disease, neurosurgery, diabetes, cancer care, and care of the homeless are among the hospital’s recognized areas of expertise. Through the Keenan Research Centre and the Li Ka Shing International Healthcare Education Centre, which make up the Li Ka Shing Knowledge Institute, research and education at St. Michael’s Hospital are recognized and make an impact around the world. Founded in 1892, the hospital is fully affiliated with the University of Toronto.

Media contact

For more information, or to arrange an interview with Dr. Ray, please contact:

Corinne Ton That
Communications and Public Affairs
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416-864-6060 ext.7178
St. Michael’s Hospital