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Unexplained differences in sex ratios at birth in Europe and North America

BMJ 2002; 324 doi: (Published 27 April 2002) Cite this as: BMJ 2002;324:1010
  1. Victor Grech, consultant (,
  2. Charles Savona-Ventura, consultantb,
  3. P Vassallo-Agius, consultant paediatricianc
  1. a Paediatric Department, St Luke's Hospital, Guardamangia MSD 09, Malta
  2. b Department of Obstetrics and Gynaecology, St Luke's Hospital
  3. c Medical School, University of Malta, Msida MSD 06, Malta
  1. Correspondence to: V Grech
  • Accepted 4 October 2001

In mammals, male live births exceed female ones. In humans, the ratio of male births to total births is expected to be 0.515. In Europe during 1990-5 this differed significantly with increasing geographical latitude.1 We analysed and compared the male to female ratio in Europe and North America over 50 years.

Methods and results

We obtained annual data on male and female live births from the World Health Organization (WHO) for the North American continent for 1958-97 and for European countries for 1950-99. Overall <3% of data were missing.

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Numbers of male, female, and total births, with calculated male:female ratios for countries included in study of sex …

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