title: Variations in male-female infant ratios among births to Canadian- and Indian-born mothers, 1990-2011: a population-based register study.
abstract: BACKGROUND
  We assessed variations in the male-female infant ratios among births to Canadian-born and Indian-born mothers according to year of birth, province and country of birth of each parent.
  
  
  METHODS
  In this population-based register study, we analyzed birth certificates of 5 853 970 singleton live births to Canadian-born and 177 990 singleton live births to Indian-born mothers giving birth in Canada from 1990 to 2011. Male-female ratios were stratified by live birth order and plotted by year of birth. Logistic regression was used to assess whether ratios varied between Canadian provinces and according to the birthplace of each parent. The deficit in the number of girls was estimated using bootstrap methods.
  
  
  RESULTS
  Among Canadian-born mothers, male-female ratios were about 1.05, with negligible fluctuations by birth order, year and province. Among Indian-born mothers, the overall male-female ratio at the third birth was 1.38 (95% confidence interval [CI] 1.34-1.41) and was 1.66 (95% CI 1.56-1.76) at the fourth or higher-order births. There was little variability in the ratios between provinces. Couples involving at least 1 Indian-born parent had higher than expected male-female ratios at the second and higher-order births, particularly when the father was Indian-born. The deficit in the expected number of girls among Indian immigrants to Canada in the study period was estimated to be 4472 (95% CI 3211-5921).
  
  
  CONCLUSIONS
  Fewer than expected girls at the third and higher-order births have been born to Indian immigrants across Canada since 1990. This trend was also seen among couples of mixed nativity, including those involving a Canadian-born mother and an Indian-born father. Fathers should be considered when investigating sex ratios at birth.
authors.affiliation: Centre for Research on Inner City Health (Urquia, Ray, Wanigaratne, O'Campo), Li Ka Shing Knowledge Institute, St. Michael's Hospital; Dalla Lana School of Public Health (Urquia, O'Campo), University of Toronto; Departments of Medicine and Obstetrics and Gynaecology (Ray), St. Michael's Hospital; Department of Family and Community Medicine (Moineddin), Faculty of Medicine, University of Toronto, Toronto, Ont.
authors.forename: Marcelo L
authors.initials: ML
authors.lastname: Urquia
authors.affiliation: Centre for Research on Inner City Health (Urquia, Ray, Wanigaratne, O'Campo), Li Ka Shing Knowledge Institute, St. Michael's Hospital; Dalla Lana School of Public Health (Urquia, O'Campo), University of Toronto; Departments of Medicine and Obstetrics and Gynaecology (Ray), St. Michael's Hospital; Department of Family and Community Medicine (Moineddin), Faculty of Medicine, University of Toronto, Toronto, Ont.
authors.forename: Joel G
authors.initials: JG
authors.lastname: Ray
authors.affiliation: Centre for Research on Inner City Health (Urquia, Ray, Wanigaratne, O'Campo), Li Ka Shing Knowledge Institute, St. Michael's Hospital; Dalla Lana School of Public Health (Urquia, O'Campo), University of Toronto; Departments of Medicine and Obstetrics and Gynaecology (Ray), St. Michael's Hospital; Department of Family and Community Medicine (Moineddin), Faculty of Medicine, University of Toronto, Toronto, Ont.
authors.forename: Susitha
authors.initials: S
authors.lastname: Wanigaratne
authors.affiliation: Centre for Research on Inner City Health (Urquia, Ray, Wanigaratne, O'Campo), Li Ka Shing Knowledge Institute, St. Michael's Hospital; Dalla Lana School of Public Health (Urquia, O'Campo), University of Toronto; Departments of Medicine and Obstetrics and Gynaecology (Ray), St. Michael's Hospital; Department of Family and Community Medicine (Moineddin), Faculty of Medicine, University of Toronto, Toronto, Ont.
authors.forename: Rahim
authors.initials: R
authors.lastname: Moineddin
authors.affiliation: Centre for Research on Inner City Health (Urquia, Ray, Wanigaratne, O'Campo), Li Ka Shing Knowledge Institute, St. Michael's Hospital; Dalla Lana School of Public Health (Urquia, O'Campo), University of Toronto; Departments of Medicine and Obstetrics and Gynaecology (Ray), St. Michael's Hospital; Department of Family and Community Medicine (Moineddin), Faculty of Medicine, University of Toronto, Toronto, Ont.
authors.forename: Patricia J
authors.initials: PJ
authors.lastname: O'Campo