A study comparing rates of preterm birth among non-Hispanic black and non-Hispanic white women in Canada found that the rates were substantially higher among black women than white women, mirroring the disparity in the United States. The research study, published in CMAJ (Canadian Medical Association Journal), is based on new cohort data from the Canadian Live Birth, Infant Death and Stillbirth Database linked with 2006 Canadian census data.
"Relative disparities in preterm birth and very preterm birth between non-Hispanic black and white women in Canada mirrored those in the US. This observation was contrary to our hypothesis, which was based on the different historical experiences of black populations in the 2 countries and evidence that socioeconomic and racial disparity in health and access to health care tend to be less extreme in Canada," writes Dr. Britt McKinnon, Institute for Health and Social Policy, McGill University, Montréal, Quebec, with coauthors.
The study included 91 045 live singleton births in Canada and just over 5 million live births in the US between May 2004 and May 2006. In Canada, 4.2% of all births were to women who self-identified as black compared with 20.5% in the US. Overall preterm birth rates were lower in Canada (6%) than in the US (9%). Preterm birth rates among black women in Canada were 8.9%, compared with 5.9% among white women. US rates were higher, at 12.7% and 8.0% respectively.
Foreign-born black women in Canada had preterm birth rates similar to those of native-born black women, unlike in the US, where foreign-born black women had lower preterm birth rates.
"We found that relative differences in preterm and very preterm birth rates between the black and white women in Canada were similar in magnitude to the racial disparities observed in the US study cohort," write the authors. "The absolute difference in preterm birth was narrower in Canada than in the US, which reflects the lower overall preterm birth rates in Canada among black and white women."
A weakness of the study was the poor quality of birth registration data from Ontario, the country's largest province, which also has the largest black population. The results, however, were similar for Ontario and elsewhere in Canada.
The authors concluded that further research should investigate whether factors like socioeconomic disadvantage, discrimination and health behaviours contribute to racial disparities in preterm birth in Canada.
In a related commentary, Dr. Russell Kirby, Department of Community and Family Health, University of South Florida, Tampa, Florida, states, "Overall, McKinnon and colleagues' findings are not surprising: the incidence of preterm birth was lower among Canadian women than among women in the US, both for infants born to white women and for those born to black women, but the increased risk for infants born to black women was generally similar across the two countries."
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