Secular trends in sex ratios at birth in North America and Europe over the second half of the 20th century

• Published in: Journal of epidemiology and community health (1979) Vol. 57; no. 8; pp. 612 - 615
• Main Authors: Grech, V, Vassallo-Agius, P, Savona-Ventura, C
• Format: Journal Article
• Language: English
• Published: London BMJ Publishing Group Ltd 01-08-2003; BMJ Publishing Group; BMJ; BMJ Publishing Group LTD; BMJ Group
• Subjects: 20th century; Analysis. Health state; Biological and medical sciences; birth rate; Birth Rate - trends; Births; Childbirth; climate; Community health; Continents; Datasets; Epidemiology; Europe - epidemiology; Female; Females; General aspects; Humans; Infant, Newborn; Infants; Latitude; Live births; Male; Male animals; Males; Medical sciences; North America - epidemiology; Public health. Hygiene; Public health. Hygiene-occupational medicine; Ratios; Regression analysis; Reproduction; Research Report; Secular variations; Sex Distribution; Sex Ratio; Statistics; Surveys; Trends; Vivipary; North America; Europe; America; Romania; United Kingdom > UK; United States > US; Spain; Greece; Canada; Netherlands; Norway; Ireland; Finland; Denmark; Poland; Mexico; France; Germany; Sex ratio; Birth
• ISSN: 0143-005X; 1470-2738
• DOI: 10.1136/jech.57.8.612

Context: A previous study showed that significantly more boys were born in southern latitudes in Europe than in northern latitudes and the converse pattern was observed in North America. Objective: This study analyses secular trends in gender ratios for live births over the second half of the 20th century. Design, setting, participants: Analysis was carried out from a World Health Organisation dataset comprising live births over the above period. This included 127 034 732 North American and 157 947 117 European live births. Main outcome measures: Analysis of trends in gender ratios for countries in both continents. Results: The findings show a highly significant overall decline in male births in both Europe and North America (p<0.0001), particularly in Mexico (p<0.0001). Interestingly, in Europe, male births declined in North European countries (latitude>40°, p<0.0001) while rising in Mediterranean countries (latitude ≅35–40°, p<0.0001). These trends produced an overall European male live birth deficit 238 693 and a North American deficit of 954 714 (total male live birth deficit 1 193 407). Conclusions: No reasonable explanation/s for the observed trends have been identified and the causes for these trends may well be multifactorial.