Doctor: Morgane Ballon

Title: Social inequalities and child’s growth

Supervisor: Barbara Heude

Doctoral school: ED 393 Epidemiology and Biomedical Information Sciences, Université Paris Cité

Date of thesis defense: 25/11/2019

Jury: Pierre-Yves Ancel, Cyrille Delpierre, Nicole Darmon, Raphaëlle Varraso, Katia Castetbon, Sandrine Lioret

Thesis summary:

Overweight and obesity are a burden for many countries around the world, especially because of their relation to many short- and long-term health problems. An inverse gradient has been described between socioeconomic position and overweight, which increases with age and over time. This gradient seems paradoxical given the positive association observed between socioeconomic position and birth weight. In this context, it is therefore important to better understand the age at which the socioeconomic gradients of weight, height, body mass index (BMI) and overweight occur, and to identify the modifiable factors involved in these inequalities of growth and overweight. To answer this question, this thesis was based on the analysis of data from two French birth cohorts, EDEN and Elfe. Our findings suggested that social inequalities of BMI and overweight, which were the manifestation of social inequalities in weight and height, emerged as early as 1 month. We also showed that pre-gestational BMI and smoking during pregnancy accounted for a large part of the relationship between maternal education level (used as a proxy for socioeconomic position) and birth weight and height (prenatal growth). In addition, smoking during pregnancy and duration of breastfeeding substantially mediated the association between maternal education level and weight growth rate at 3 months (postnatal growth). These original findings suggest that the reduction of social inequalities in growth and child overweight could be achieved through prevention programs focused on perinatal factors like pre-gestational BMI, smoking during pregnancy and breastfeeding, especially amongst the most socially disadvantaged families

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