02/15/2012 07:01 EST | Updated 04/16/2012 05:12 EDT

Newborn Birth Weight Chart Could Help Immigrants


TORONTO - It's one of the first questions people ask new parents after finding out whether their newborn is a boy or a girl: how much does the baby weigh?

For immigrant parents who have come to Canada from certain parts of the world, that question — and the answer — can induce a lot of stress.

That's because infants of immigrant parents, especially those from countries such as China and India, can be misdiagnosed as being underweight compared to the long-established Canadian "norm," suggesting they could potentially be subject to developmental disorders as they mature.

"When those babies are weighed, whether a boy or a girl and from whatever ethnic background, that baby will be deemed to be at appropriate size at birth or small for gestational age, meaning small for the time point at which the baby was born," said Dr. Joel Ray.

"We then need to as caregivers, people who talk to parents and explain things and weigh babies, we need to ensure those babies are being ascribed their correct definition of small for gestational age," said Ray, a maternal medicine specialist at St. Michael's Hospital in Toronto.

However, he said birth-weight charts, or curves, used by many Canadian hospitals and clinics are based on outmoded data that don't reflect the naturally smaller stature of some immigrant populations and their offspring.

"These babies whose moms come from south Asia or east Asia ... these babies are smaller, they're considerably smaller," said Ray, noting that many would be misclassified as underweight based on conventional charts.

On Wednesday, Ray and colleagues published a new set of birth-weight curves in the Journal of Obstetrics and Gynaecology Canada. The charts are based on a study of 760,000 live births in Ontario, home to 55 per cent of Canada's immigrants.

The team found that infants born to mothers from each region of the world, except Europe and other Western countries, had significantly lower birth weights — up to 250 grams less — than those for infants of Canadian-born mothers.

The study showed that 67 of every 1,000 babies born to parents from Africa or the Caribbean and 116 of every 1,000 South Asian babies were at risk of being labelled as significantly underweight if plotted on a conventional curve instead of the proposed region-specific charts.

"We have a major problem on our hands if we misclassify a whole bunch of south Asian newborns as small when in fact they're not ... they're appropriate for their own ethnicity," he said.

"That doesn't make a new immigrant couple, who are just looking forward to having a baby and don't need stress or distraction from that joy, to be (told) their baby is small on the birth-weight chart. And it probably doesn't make them feel better, even when it's qualified."

Ray said newborns deemed to be underweight may be given unnecessary tests to make sure there is nothing physiologically wrong that led to their being smaller, and followup visits to their pediatrician due to concerns about whether the baby's health potential is being maximized.

On the flip side of the study, the researchers looked at how many babies were being incorrectly labelled as too heavy, or "large for gestational age."

They determined that prenatal caregivers using current Canadian charts would fail to identify a significant percentage of southeast Asian-Pacific and south Asian babies that are big compared to others in their ethnic groups.

When correctly diagnosed, these babies may need to be delivered early to prevent potential injury during birth and to avoid unnecessary caesarean sections.

But properly designating a newborn as large for their ethnic background can also act as a red flag for parents to watch out for obesity as their child grows.

Miao Li, who immigrated to Toronto from China, and her Canadian-born Caucasian husband recently welcomed a new addition to their family — son Malik, who at birth tipped the scales at nine pounds.

Because her baby "looked very big" when he was born three weeks ago, Li was worried about obesity, thinking her child could already be overweight.

"So far, no doctor is talking about overweight, even now at 22 days, compared to other newborn babies," she said Tuesday during a checkup at the pediatric clinic at St. Michael's Hospital. "My concern is overweight, but I asked the doctor many times and he said: 'No, it's OK.'"

Ray said the new charts will be available online for health providers to use and he hopes they will be adopted by such organizations as the Canadian Paediatric Society.

“By implementing our modified birth-weight charts, a large number of newborns will be spared an unnecessarily prolonged stay in hospital, special biochemical and genetic testing, and followup with a general or developmental pediatrician,” said Ray. “This lowers the burden on not only the child and their parent, but also on limited in-hospital and pediatric clinic resources."

The Canadian Paediatric Society declined to comment on the birth-weight charts developed by the hospital's researchers, saying its committee would first need to review them.

The CPS follows recommendations by the World Health Organization, which in 2006 released international growth charts for children from birth to age five, based on data from children raised in six different countries — Brazil, Ghana, India, Norway, Oman and the United States — according to recommended nutritional and health guidelines.