Abstract
Objectives
The objective of this study was to investigate whether any observed trends in birthweight are accompanied by changes in maternal sociodemographic characteristics, including age, marital status, and education.
Methods
We conducted a population-based study of term singletons born in Newfoundland and Labrador, Canada, between 1992 and 2005 (N=66,638). Large-sample significance tests for two population proportions were used to test whether differences in mean birthweight, the proportion of low and high birthweight infants, and differences in maternal socio-demographic characteristics between 1992–95 and 2002–05 were statistically significant. Chi-square tests were used to test for associations between birthweight group and maternal age, education and marital status. Multivariate logistic regression was used to examine the interaction of these effects across time periods.
Results
Of the 66,638 infants included in the study, 54,256 (81.4%) were born in the normal birthweight range (2500-4000 grams) while 11,305 (17.0%) were high birthweight (>4000 grams) and 1,077 (1.6%) were low birthweight (<2500 grams). The rate of low birthweight significantly decreased from 1992 to 1995 compared to the period 2002 to 2005 (1.9% to 1.3%: p<0.01). The rate of high birthweight significantly increased over the same two time periods (16.2% to 17.5%: p<0.01). Mean birthweight increased from 3529 grams to 3566 grams (p<0.01). Compared to women who had babies from 1992 to 1995, women who gave birth from 2002 to 2005 were more likely to be older, have higher levels of education, and never have been married. Birthweight outcomes were significantly associated with mother’s age, education and marital status.
Conclusion
Changes in maternal demographics are associated with the upward shift in birthweight in Newfoundland and Labrador.
Key words: Birth weight, trends, full-term infants, Newfoundland and Labrador
Résumé
Objectif
Déterminer si les tendances observées dans le poids de naissance s’accompagnent de changements dans le profil sociodémographique des mères (âge, état matrimonial et scolarité).
Méthode
Nous avons mené une étude représentative des bébés uniques nés à terme à Terre-Neuve-et-Labrador, au Canada, entre 1992 et 2005 (N=66 638). À l’aide de tests d’hypothèses pour grand échantillon menés sur deux sous-populations, nous avons déterminé si les écarts dans le poids de naissance moyen, les proportions de nourrissons présentant une insuffisance ou un excédent de poids à la naissance, et le profil sociodémographique des mères entre 1992–1995 et 2002–2005 étaient significatifs. À l’aide de tests du khi-carré, nous avons testé les associations entre les deux groupes de poids de naissance et l’âge, la scolarité et l’état matrimonial des mères. Par analyse de régression logistique multivariée, nous avons examiné l’interaction de ces effets dans le temps.
Résultats
Sur les 66 638 nourrissons inclus dans l’étude, 54 256 (81,4 %) avaient un poids normal à la naissance (2 500 à 4 000 g); 11 305 (17 %) avaient un excédent de poids à la naissance (>4 000 g), et 1 077 (1,6 %) avaient un poids insuffisant à la naissance (<2 500 g). Le taux d’insuffisance de poids à la naissance a significativement diminué entre 1992 et 1995 comparé à la période de 2002 à 2005 (de 1,9 % à 1,3 %: p<0,01). Le taux d’excédent de poids à la naissance a significativement augmenté sur les deux mêmes périodes (de 16,2 % à 17,5 %: p<0,01). Le poids de naissance moyen a augmenté, passant de 3 529 g à 3 566 g (p<0,01). Comparées aux femmes ayant accouché entre 1992 et 1995, celles qui ont accouché entre 2002 et 2005 étaient plus susceptibles d’être plus âgées, plus scolarisées et de n’avoir jamais été mariées. Le poids de naissance présentait une corrélation significative avec l’âge, la scolarité et l’état matrimonial de la mère.
Conclusion
Les changements dans le profil démographique des mères sont associés à la tendance haussière du poids de naissance des bébés à Terre-Neuve-et-Labrador.
Mots clés: poids de naissance, tendances, naissance à terme, Terre-Neuve-et-Labrador
Footnotes
Acknowledgements: This work was supported by the Newfoundland and Labrador Centre for Health Information. Our thanks to Dr. Don MacDonald, Senior Director of Research and Evaluation, Newfoundland and Labrador Centre for Health Information; Dr. Barbara Roebothan, Associate Professor of Community Health and Biochemistry, Memorial University of Newfoundland; and Mr. Steve O’Reilly, Executive Director, Atlantic Canada, Canadian Institute for Health Information, for their comments and suggestions throughout the course of this work.
Conflict of Interest: None to declare.
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