Hausse récente de la fécondité en Haïti : un nouvel engouement pour la vie en union ?

Trois enquêtes démographiques rétrospectives ont été réalisées à Haïti en 1977, 1983 et 1987. Elles font apparaître une hausse de la fécondité, tant sur les indices synthétiques des périodes précédant les enquêtes que sur les parités moyennes (nombre total d'enfants déjà nés suivant l'âge des femmes enquêtées). La validité du résultat obtenu est appréciée en comparant les données des enquêtes à celles d'autres sources (autres enquêtes, recensements), en étudiant la cohérence interne de chaque enquête (comparaison des indices synthétiques de fécondité du moment et des descendances des générations) et en rapprochant les résultats des trois enquêtes (calcul d'indices du moment par différence entre les parités atteintes dans deux enquêtes ou reconstitution des parités à une même date à partir de deux enquêtes). Le facteur essentiel d'incertitude semble lié à l'émigration vers les Etats-Unis des femmes les moins fécondes. La plus grande précocité de la vie en union et la prédominance accrue des formes conjugales impliquant la cohabitation des partenaires sont les facteurs essentiels de la hausse de la fécondité. Le phénomène touche davantage les femmes les moins instruites, sans doute parce que ce sont elles qui ont le plus besoin de la sécurité financière qu'offre la vie en couple dans une période économique particulièrement difficile pour Haïti. (Résumé d'auteur

Time Trend of the Male Proportion at Birth in Brazil, 1979–2004

Several studies suggest that exposure to environmental endocrine disrupters can reduce the number of male births, and therefore, the male proportion at birth (also denominated birth ratio or sex ratio at birth) can be used as a sentinel health indicator. This work aimed to analyze the trend of male births in Brazil, according to their distribution by states and capitals. An ecological descriptive time series was carried out using polynomial regression, showing a declining trend for male proportion at birth in Brazil (1979–1994), followed by an upward trend until 2004. A decline on the proportion of male births was observed in Brazil between 1979 and 1993, followed by a subsequent rise of this ratio between 1995 and 2004, wherein the mean proportion of male births in Brazil rose from 51.05 to 51.18, representing a relative increase of 0.25%. The states of São Paulo (Southwest region) and Acre (Western Amazon), as well as some capitals–Cuiabá (Western Region), Palmas (Amazon) and Rio Branco (Amazon)–showed increasing trends, which suggests the influence of socio-demographic changes. In contrast, a declining trend in the State of Ceará State (Northeast region), with a 0.35% yearly decrease was observed. As a whole, these results suggest the influence of different environmental factors (demographic changes, public health services distribution, and population exposure to endocrine disruptor substances) influencing the time trend of birth ratio in the Brazilian population during the last decades

Maternal exposure to polychlorinated biphenyls and the secondary sex ratio: an occupational cohort study

Though commercial production of polychlorinated biphenyls was banned in the United States in 1977, exposure continues due to their environmental persistence. Several studies have examined the association between environmental polychlorinated biphenyl exposure and modulations of the secondary sex ratio, with conflicting results. Our objective was to evaluate the association between maternal preconceptional occupational polychlorinated biphenyl exposure and the secondary sex ratio. We examined primipara singleton births of 2595 women, who worked in three capacitor plants at least one year during the period polychlorinated biphenyls were used. Cumulative estimated maternal occupational polychlorinated biphenyl exposure at the time of the infant's conception was calculated from plant-specific job-exposure matrices. A logistic regression analysis was used to evaluate the association between maternal polychlorinated biphenyl exposure and male sex at birth (yes/no). Maternal body mass index at age 20, smoking status, and race did not vary between those occupationally exposed and those unexposed before the child's conception. Polychlorinated biphenyl-exposed mothers were, however, more likely to have used oral contraceptives and to have been older at the birth of their first child than non-occupationally exposed women. Among 1506 infants liveborn to polychlorinated biphenyl-exposed primiparous women, 49.8% were male; compared to 49.9% among those not exposed (n = 1089). Multivariate analyses controlling for mother's age and year of birth found no significant association between the odds of a male birth and mother's cumulative estimated polychlorinated biphenyl exposure to time of conception. Based on these data, we find no evidence of altered sex ratio among children born to primiparous polychlorinated biphenyl-exposed female workers

Can environmental or occupational hazards alter the sex ratio at birth? A systematic review

More than 100 studies have examined whether environmental or occupational exposures of parents affect the sex ratio of their offspring at birth. For this review, we searched Medline and Web of Science using the terms ‘sex ratio at birth’ and ‘sex ratio and exposure’ for all dates, and reviewed bibliographies of relevant studies to find additional articles. This review focuses on exposures that have been the subject of at least four studies including polychlorinated biphenyls (PCBs), dioxins, pesticides, lead and other metals, radiation, boron, and g-forces. For paternal exposures, only dioxins and PCBs were consistently associated with sex ratios higher or lower than the expected 1.06. Dioxins were associated with a decreased proportion of male births, whereas PCBs were associated with an increased proportion of male births. There was limited evidence for a decrease in the proportion of male births after paternal exposure to DBCP, lead, methylmercury, non-ionizing radiation, ionizing radiation treatment for childhood cancer, boron, or g-forces. Few studies have found higher or lower sex ratios associated with maternal exposures. Studies in humans and animals have found a reduction in the number of male births associated with lower male fertility, but the mechanism by which environmental hazards might change the sex ratio has not yet been established

How do demographic trends change? The onset of birth masculinization in Albania, Georgia, and Vietnam 1990–2005

The theory of demographic transistion assumes the gradual move from a pre-transitional equilibrium of birth and death rates to a new equilibrium corresponding to lower vital rates. While this model remains largely correct,research on more than two centuries of demographic change has pointed to a signifcant number of variants and departures from the model. For instance, the secular decline in vital rates was often preceded by a short-term rise, starting from different high-fertility levels (Dyson and Murphy1985), and was at times followed by unexpected stalls and rebounds as in post war Europe (Van Bavel and Reher 2013), Southeast Asia (Hull 2012),sub-Saharan Africa (Shapiro and Gebreselassie 2013), and Central Asia(Spoorenberg 2015)

Nuptialité et transition démographique en Malaisie occidentale

Thèse de maîtrise en démographie -- UCL, 198