Maternal nutrition before pregnancy, fetal growth and placental epigenetics

Doctor: Marion Lecorguillé

Title: Maternal nutrition before pregnancy, fetal growth and placental epigenetics

Supervisors: Marie-Aline Charles, Barbara Heude

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

Date of thesis defense: 13/10/2020

Jury: Marie-Aline Charles, Barbara Heude, Gianluca Severi, Dominique Darmaun, Johanna Lepeule, Rachel Lévy, Jean-Louis Guéant

Thesis summary:

Maternal diet plays a major role for fetal development from the preconception period. In recent years, new research has shown the involvement of some nutrients (vitamins B2, B6, B9, B12, methionine, betaine and choline) in major epigenetic processes that take place in early pregnancy, particularly DNA methylation. The first objective was to explore the association between dietary intake of micronutrients involved in epigenetic mechanisms in the year before pregnancy with fetal development; and placental DNA methylation. We identified three dietary patterns explaining the variability of combined micronutrients intake among young women of childbearing age in the EDEN mother-child cohort: “varied and balanced”, “vegetarian tendency”, and “bread and starchy rich food”. We did not find any major effect of preconception intake of nutrients involved in methylation pathways on fetal growth and nor on placental DNA methylation. However, our results highlighted an association between these patterns and differentially methylated regions located on genes involved in various functions and metabolic processes essential for embryonic development. Recent changes in eating habits also place us in a context where the prevalence of overweight and obesity has increased in the last years. Many studies have reported that maternal weight status at conception was associated with child development, but few studies have focused on pre-pregnancy weight changes that reflect however the maternal nutritional and metabolic status at conception. In a second step, we evaluated whether maternal weight change in the year before pregnancy may influence birth weight. In the national Elfe birth cohort, we observed that in overweight or obese women, pre-pregnancy weight loss was associated with a decrease in birth weight, but this effect was offset by excessive gestational weight gain. This work contributes to a better understanding of the impact of nutritional exposures during the preconception period on fetal growth. They encourage further research around this key period, in order to help develop messages to prevent overweight or obesity and to promote a varied and balanced diet with the aim of improving the health of women who want a pregnancy.