How much a baby weighs at birth can tell a lot about his or her health. And common wisdom suggests the bigger the baby, the better.
It turns out this often is not the case for immigrant families. Yet many of them are still told their babies are significantly underweight and may be at risk for developmental problems as a result. It can be a major source of stress for new parents.
Now, researchers at Toronto's St. Michael's Hospital say many of these "underweight" infants are perfectly healthy and what needs to change is the yardstick used to assess birth weight.
The problem, they say, is many babies of South Asian, African, Caribbean or other ethnic heritage are being unfairly compared to infants born to Canadian mothers.
Researchers were not able to identify the ethnic background of the Canadian-born women that were used as a comparison against women born in other parts of the world. The study notes that mothers included in the study period would have been born 25 to 35 years ago, when the major ethnic group in Canada was British and European.
It's now becoming clear that infants belonging to certain ethnic groups are naturally smaller.
Similar findings are also reshaping what is considered normal weight for adults of various ethnic backgrounds. For instance, a normal body mass index and waist circumference for South Asian men and women is actually lower than it is for Canadian-born adults.
St. Michael's Hospital doctor Joel Ray and colleagues have today published the country's first newborn weight curves that can be applied to different ethnic groups in Canada. The curves compare a baby's weight to others at similar ages. The new guidelines appear in the Journal of Obstetrics and Gynaecology Canada.
In his research, Dr. Ray looked at 760,000 live births in Ontario and found infants born to mothers from every region of the world, except Western countries, had significantly lower birth weights.
The research notes that 67 out of every 1,000 babies born to African or Caribbean-born parents were at risk of being classified as significantly underweight, based on standard Canadian birth weight curves. The same is true for 116 out of every 1,000 South Asian infants.
"That's unacceptable in my mind," Dr. Ray said in a news release. "There are all these parents who are very excited about having a baby, and now they might have concerns their baby is not big enough—something that it not true and not especially welcoming."
The findings could have significant implications because birth weight is one of the primary tools used to assess a newborn's health.
"Our findings have potential impact in several ways," Dr. Ray said. "The number of new immigrant parents and infants affected is sizable, meaning that there is a large target group in need of new birthweight curves."
Editor's note: This blog was updated with additional information relating to the ethnic background of Canadian mothers looked at in the study.