• Marcelo L Urquia, Rahim Moineddin, Prabhat Jha, Patricia J O'Campo, Kwame McKenzie, Richard H Glazier, David A Henry, and Joel G Ray.
• Centre for Global Health Research (Jha), St. Michael's Hospital; Centre for Research on Inner City Health (Urquia, O'Campo, Glazier), Li Ka Shing Knowledge Institute, St. Michael's Hospital; Departments of Medicine, and Obstetrics and Gynecology (Ray), St. Michael's Hospital; Dalla Lana School of Public Health (Urquia, Jha, O'Campo, Henry), University of Toronto; Department of Family and Community Medicine (Moineddin, Glazier), University of Toronto; Centre for Addiction and Mental Health (McKenzie), University of Toronto; Department of Psychiatry (McKenzie), University of Toronto; Institute for Clinical Evaluative Sciences (Urquia, Moineddin, O'Campo, Glazier, Henry, Ray), Toronto, Ont. urquiam@smh.ca.
• CMAJ. 2016 Jun 14; 188 (9): E181-90.

BackgroundSkewed male:female ratios at birth have been observed among certain immigrant groups. Data on abortion practices that might help to explain these findings are lacking.MethodsWe examined 1 220 933 births to women with up to 3 consecutive singleton live births between 1993 and 2012 in Ontario. Records of live births, and induced and spontaneous abortions were linked to Canadian immigration records. We determined associations of male:female infant ratios with maternal birthplace, sex of the previous living sibling(s) and prior spontaneous or induced abortions.ResultsMale:female infant ratios did not appreciably depart from the normal range among Canadian-born women and most women born outside of Canada, irrespective of the sex of previous children or the characteristics of prior abortions. However, among infants of women who immigrated from India and had previously given birth to 2 girls, the overall male:female ratio was 1.96 (95% confidence interval [CI] 1.75-2.21) for the third live birth. The male:female infant ratio after 2 girls was 1.77 (95% CI 1.26-2.47) times higher if the current birth was preceded by 1 induced abortion, 2.38 (95% CI 1.44-3.94) times higher if preceded by 2 or more induced abortions and 3.88 (95% CI 2.02-7.50) times higher if the induced abortion was performed at 15 weeks or more gestation relative to no preceding abortion. Spontaneous abortions were not associated with male-biased sex ratios in subsequent births.InterpretationHigh male:female ratios observed among infants born to women who immigrated from India are associated with induced abortions, especially in the second trimester of pregnancy.© 2016 Canadian Medical Association or its licensors.

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