Canada would rank higher on international child health indexes if unstandardized measurements of infant mortality rates in other countries didn't skew the calculations, a new study says.

The research, conducted by four Canadian universities and the Public Health Agency of Canada, shows surveys on perinatal, infant and child mortality rates conducted by the United Nations Children's Fund (UNICEF) and the Organization for Economic Co-operation and Development (OECD) are biased because many countries fail to register all babies, especially those born very small or too early.

In Canada and the U.S., authorities must register all babies that are born alive, but many European countries do not record babies who die before they reach 24 weeks of age in their overall infant mortality rate, said the study's lead author, Dr. K. S. Joseph, a professor in the University of British Columbia's department of obstetrics and gynecology.

"That minimizes the number of baby deaths you have in a country if you do not register the ones who are very, very likely to die, the very tiny ones," he told CBC News.

Canada ranks 18th among developed nations

The study, published in the British Medical Journal on Friday, was conducted by researchers from the University of British Columbia, Dalhousie University, McGill University, the University of Calgary and the Public Health Agency of Canada.

Canada ranked 18th on a 2004 UNICEF survey among OECD nations for the overall infant mortality rate, with the United States placing 22nd.

If corrected neonatal mortality rates calculations are applied, however, Canada and the U.S. would have ranked 12th and 11th, respectively, the researchers say.

The researchers used 2004 data from Australia, Canada, Europe and the United States, and compared fetal, neonatal and infant mortality rates, including data for babies at all ages.

"We've gone and used data where we had information on all countries, so that we could compare apples with apples, instead of taking the overall figure given out by each country," Joseph told CBC News.

Comparisons were also made using data for 2007 from Australia, Canada and New Zealand.

Wide variations in birth registration procedures

The researchers' analysis found wide variations in birth registration procedures, even in industrialized countries.

In turn, countries that only register infants who survived, or who had a reasonable chance of survival, ranked better on the survey, the researchers said.

"The highly publicized, poor OECD rankings of Canada and the U.S. are almost entirely attributable to the selective registration in other countries of extremely preterm infants who survive, and the systematic under-registration of those who don't," Michael Kramer, one of the study's authors, said in a statement on Friday.

"It is also important to note that the poor international rankings do not reflect inferior quality of, or access to, health care for pregnant women or newborn infants in Canada and the United States. Correcting for this problem, as is recommended by the World Health Organization, will show that our countries perform extremely well," said Kramer.

Joseph said the rankings of industrialized countries by infant mortality and other related indices are "extremely misleading."

"Appropriate steps should be taken to standardize birth registration and related data quality issues if we are to fully understand infant health status in industrialized countries," Dr. Joseph added in a statement Friday.