Rationale & Background: Gaining excessive adiposity in pregnancy is associated with altered cardiometabolic profile and adverse pregnancy outcomes. Lifestyle interventions may reduce excess weight gain, but the effect on fat gain is unclear. Our study explored this question by 1) comparing measures of body fat (BF) by bioelectrical impedance analysis (BIA) and 4-site skinfold thickness (SFT); 2) assessing the impact of a nutrition+exercise intervention on adiposity changes; 3) elucidating associations between adiposity changes and cardiometabolic biomarkers and adverse pregnancy outcomes. Study Design: Participants randomized to receive a high dairy protein diet and exercise program (intervention) or standard care (control) in the Be Healthy in Pregnancy RCT (NCT 01689961) had adiposity measured at 12-17, 26-28, and 36-38 weeks gestation by BIA (%BF) and SFT (sum and %BF), and at 6 months postpartum also by DXA. Fasted blood samples collected at 12-17 and 36-38 weeks gestation were analyzed for glucose, lipid profile, insulin, leptin, adiponectin, and CRP. Pregnancy outcomes were abstracted from medical charts. Results: In 181 participants, BIA %BF and SFT %BF had good agreement in early pregnancy and postpartum, but low agreement in late pregnancy. Adiposity changes across pregnancy were similar between study arms but were greater in normal weight compared to overweight women. Insulin and leptin were negatively associated with change in SFT (sum and %BF). Triglycerides were negatively associated with change in BIA %BF, while HDL was positively associated. Neither caesarean section nor operative vaginal delivery were associated with adiposity change. Conclusion: Adiposity measured by sum of SFT and BIA %BF increased across pregnancy but was not influenced by the diet+exercise intervention. Associations of adiposity change with cardiometabolic biomarkers varied between measurement tools. The lack of adiposity measurement tools appropriate across pregnancy and in clinical settings presents a concern for assessing clinical responses to adiposity change across pregnancy. / Thesis / Master of Science (MSc) / Pregnancy is associated with a natural gain in body fat, but it can reach excessive amounts. Excess body fat is of clinical consequence as it is associated with poor cardiovascular health and abnormal pregnancy outcomes. Improving diet and physical activity habits may reduce excess weight gain, but little is known about how it influences fat gained during pregnancy. In our study body fat gain during pregnancy was similar between the lifestyle intervention and control groups. However, entering pregnancy with greater BMI was associated with less fat gain during pregnancy. Changes in body fat influenced cardiovascular blood markers, but results differed between body fat assessment tools. We also found that methods to measure body fat produce different results at different stages of pregnancy. Our findings provide insight on the factors that influence fat gain during pregnancy and highlight the need for better tools to measure body fat accurately in pregnancy.

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La nutrition périnatale conditionne durablement les fonctions physiologiques, avec des conséquences sur la susceptibilité à développer des maladies métaboliques à l’âge adulte. Le microbiote représente un des acteurs de cette empreinte nutritionnelle. L’objectif est de déterminer chez le porc l’impact d’une supplémentation périnatale en fructo-oligosaccharides à courte chaîne (scFOS) sur le développement des fonctions immunitaires et endocrines intestinales et les conséquences sur la santé métabolique de l’adulte en situation de déséquilibre nutritionnel.La supplémentation maternelle en scFOS, en modifiant le microbiote de la mère et de la descendance et la qualité du lait, accélère la maturation du système immunitaire intestinal des porcelets allaités.La fenêtre d’exposition (maternelle vs post-sevrage) conditionne la nature des modifications immunes induites par les scFOS. La supplémentation périnatale en scFOS modifie la réponse métabolique de l’adulte à un régime déséquilibré en stimulant la fonction endocrine intestinale et la sensibilité du pancréas au glucose, en réduisant les risques d’inflammation, et en modifiant l’homéostasie métabolique, associé à des modulations du microbiote.En résumé, la consommation périnatale de prébiotiques programme le phénotype métabolique et immunitaire de l’adulte via des modulations persistantes du microbiote. L'approche intégrée des données a permis d’identifier des acteurs moléculaires impliqués dans l’adaptation différentielle des individus à un régime déséquilibré en fonction de leur alimentation périnatale. / Perinatal scFOS supplementation modifies metabolic response to an unbalanced diet in adults by stimulating intestinal endocrine function and pancreas sensitivity to glucose, by reducing risks of inflammation, and in fine by changing metabolic homeostasis in association with modifications of microbiota.In summary, prebiotic consumption during perinatal life programs the immune and metabolic phenotype of adults through persistent modulations of intestinal microbiota. The integrated approach of data enables us to identify molecular actors involved in the differential adaptation of individuals to an unbalanced diet according to their perinatal nutrition.