C-section birth increases offspring obesity risk dependent on maternal diet and obesity status in rats

Delivery by cesarean section leads to heavier adult bodyweight in prairie voles (Microtus ochrogaster)

Delivery by cesarean section now makes up 32.1 % of all births in the United States. Meta-analyses have estimated that delivery by cesarean section is associated with a > 50 % increased risk for childhood obesity by 5 years of age. While this association is independent of maternal obesity, breastfeeding, and heritable factors, studies in humans have been unable to test for a causal role of cesarean delivery in this regard. Here, we set out to use an animal model to experimentally test whether delivery by cesarean section would increase offspring weight in adulthood. Delivery by cesarean section may exert neurodevelopmental consequences by impacting hormones that are important at birth as well as during metabolic regulation in later life, such as oxytocin and vasopressin. The prairie vole (Microtus ochrogaster) has long been studied to investigate the roles of oxytocin and vasopressin in brain development and social behavior. Here, we establish that prairie voles tolerate a range of ambient temperatures, including conventional 22° housing, which makes them translationally appropriate for studies of diet-induced obesity. We also studied vole offspring for their growth, sucrose preference, home cage locomotor activity, and food consumption after birth by either cesarean section or vaginal delivery. At sacrifice, we collected measures of weight, length, and adipose tissue to analyze body composition in adulthood. Voles delivered by cesarean section had consistently greater bodyweights than those born vaginally, despite having lower food consumption and greater locomotive activity. Cesarean-delivered animals were also longer, though this did not explain their greater body weights. While cesarean delivery had no effect on vasopressin, it resulted in less oxytocin immunoreactivity within the hypothalamus in adulthood. These results support the case that cesarean section delivery plays a causal role in increasing offspring body weight, potentially by affecting the oxytocin system.

Cesarean delivery and insulin sensitivity in the older adult: The Microbiome and Insulin Longitudinal Evaluation Study

The present study was designed to evaluate if mode of delivery at birth is associated with body mass index (BMI) and glucose homeostasis traits in later life, controlling for possible confounders, including maternal history of diabetes. Data were obtained through a racially diverse, prospective cohort study of nondiabetic, older adults, the Microbiome and Insulin Longitudinal Evaluation Study (MILES). We used generalized linear models to estimate the association between mode of delivery and glycemic status, BMI (kg/m²), waist circumference (cm), fasting glucose, fasting insulin, insulin secretion, insulin sensitivity, and insulin clearance. Further, we estimated the direct and indirect effects of cesarean delivery on glucose and insulin-related traits, as mediated by BMI status. Relative to vaginal delivery, cesarean delivery was associated with a significantly higher BMI (adjusted beta [aβ] 3.53 kg/m²; 95% CI 0.15, 6.91) and fasting glucose (aβ 5.12; 95% CI 0.01, 10.23), a 14% decrease in insulin sensitivity (aβ –0.14; 95% CI –0.28, –0.01), and a 58% increased risk (adjusted relative risk [aRR] 1.58; 95% CI 1.08, 2.31) for prediabetes/diabetes. Associations were mediated in part by BMI, with the strongest evidence observed for glycemic status (proportion mediated 22.6%; P = .03), fasting insulin (proportion mediated 58.0%; P = .05), and insulin sensitivity index (proportion mediated 45.9%; P = .05). Independent of mediation, a significant direct effect of cesarean delivery on glycemic status was observed (aRR 1.88; 95% CI 1.16, 2.60). Cesarean delivery may lead to reduced insulin sensitivity and, ultimately, increased risk for developing prediabetes and diabetes.