Document Detail

Sex ratios: are there natural variations within the human population?
MedLine Citation:
PMID:  9307533     Owner:  NLM     Status:  MEDLINE    
OBJECTIVE: To investigate on a population basis the suggestion that certain factors naturally alter the odds of having a boy or a girl, and that some women are predisposed towards having children of one particular gender. DESIGN: Routine data analysis. POPULATION: Routinely collected data on singleton infants born in Scotland from 1975 to 1988, linked so that births (live and still) to the same mother could be identified. The analyses relate to 549,048 first to fifth order births occurring to 330,088 women whose records were complete from the first delivery onwards. MAIN OUTCOME MEASURES: Gender of infant. RESULTS: Of 549,048 births, 51.4% were male. Apart from random variation, the sex ratio of 1.06 remained constant at all birth orders (P = 0.18). The probability of a male infant appeared unrelated to the genders of the preceding siblings (P > 0.20 in second to fifth deliveries), and there was no evidence of variation with maternal age (P = 0.31), maternal height (P = 0.69), paternal social class (P = 0.12), maternal social class (P = 0.57), year of delivery (P = 0.84) or season of birth (P = 0.41). Whilst mothers whose children were all the same gender were more likely to continue childbearing than those with children of different genders, there was no evidence that those with daughters were more likely to continue than those with sons. CONCLUSIONS: The suggestion that some women have a natural predisposition towards having children of a particular gender is not supported by these data. On a population basis there is no evidence to suggest that gender determination is anything other than a chance process.
N Maconochie; E Roman
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  British journal of obstetrics and gynaecology     Volume:  104     ISSN:  0306-5456     ISO Abbreviation:  Br J Obstet Gynaecol     Publication Date:  1997 Sep 
Date Detail:
Created Date:  1997-10-23     Completed Date:  1997-10-23     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  7503752     Medline TA:  Br J Obstet Gynaecol     Country:  ENGLAND    
Other Details:
Languages:  eng     Pagination:  1050-3     Citation Subset:  AIM; IM    
Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, UK.
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MeSH Terms
Birth Order
Family Characteristics
Population Surveillance
Scotland / epidemiology
Sex Ratio*

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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