Dr. Joel Ray of St. Michael's Hospital in Toronto and colleagues said the typical male born child to an immigrant mother in Ontario weighed 4 ounces more than babies born in the mother's native country.
"Nearly all infants born to women in their native country have lower birth weights than those born to mothers who had [immigrated] to Canada," Ray said in a statement.
Ray said he was not sure why the weight differences exist, but it might be a byproduct of an immigration policy that selects more robust and well-off immigrants, or immigrants might ingest more calories and exercise less than in their native countries -- resulting in bigger babies.
However, Swedish and Israeli boys and girls were bigger when born in their native countries, perhaps because of the high levels of healthcare and social services in Sweden, or the small number of babies born to Swedish immigrants in Ontario.
For Israelis, the explanation may be the higher rate of obesity among women of child-bearing age and-or the possibility Israelis do not systematically gain weight after arriving in Canada as some other immigrants do, Ray said.
Ray's paper was based on a systematic review of all birth weights between 1980 and 2012 in 21 countries accounting for 13.3 million single male births and 12.9 single female births at 40 weeks gestation.
The findings appear online in the journal Paediatric and Perinatal Epidemiology.