The Influence of Birth Order on Birth Weight: Does the Sex of Preceding Siblings Matter?
Référence bibliographique 
Côté, Karine, Blanchard, Ray et Lalumière, Martin L. 2003. «The Influence of Birth Order on Birth Weight: Does the Sex of Preceding Siblings Matter? ». Journal of Biosocial Science, vol. 35, no 3, p. 455-462.
Intentions : « The purpose of this study was to investigate whether the well-established relationship between parity and birth weight is affected by the sex composition of siblings, especially for male newborns. » (p. 455)
Échantillon/Matériau : « Subjects were 856 male ans 862 female newborns who weighed at least 2500 g at birth, who were born after 37 completed weeks of gestation, whot obtained an Apgar score of 7 or higher, who had the same biological parents as all other children in the sibship, and who lived in the samed household. » (p. 455) Longitudinal Study of Child Development in Quebec (ÉLDEQ)
Instruments : - Computerized Questionnaire Completed by the Interviewer (CQCI); - Medical files/records.
Type de traitement des données : Analyse statistique
This study is about the relationship between birth order, sex and birth weight of newborns. « [...] [R]esults showed that male newborns with the older brothers weighed less than male newborns with the older sisters. In contrast, the weight of female newborns with older brothers did not differ from the weight of female newborn with older sisters. One explanation of these results is that maternal immunoreactivity to some male-specific feature of the fetus affects prenatal development and consequently reduces birth weight in males. The relation between older brothers and birth weight may have theoretical signifiance for behavioural variables. » (p. 455)