Placental Morphology and Metabolomic Profile in Uncomplicated Metabolically Healthy Obese Pregnancy

Background/Objectives: Individuals with metabolically healthy obesity (MHO) and metabolically unhealthy obesity (MUO) in pregnancy are two distinct cardiometabolic populations, each potentially necessitating alternative clinical management. However, our understanding of the unique physiological effects of uncomplicated MHO on fetoplacental growth and metabolism remains limited. In this study, we aimed to identify changes in placental morphology and metabolites associated with maternal obesity, independent of pregnancy-related cardiometabolic complications. Methods: Placentae from women with a prepregnancy body mass index (BMI) < 25 kg/m² (control; n = 15) and women with MHO (prepregnancy BMI > 30 kg/m² with no cardiometabolic diseases; n = 15) were analyzed for indices of placental growth and untargeted metabolomics. Complementary assessments were conducted on proinflammatory genes and antioxidant defense system genes, proteins, and enzymes, along with lipid peroxidation markers. Results: Clear placentomegaly without histopathological changes was observed in uncomplicated MHO pregnancies. The metabolite 3-aminoisobutanoic acid emerged as the top-ranked feature distinguishing placentae from MHO individuals from control placentae, and changes in the cysteine, methionine, and vitamin B6 metabolism pathways were among the most distinct differences identified. Conclusions: These findings illustrate an altered placental morphology and metabolomic profile specific to uncomplicated MHO, offering new insights into how obesity, without cardiometabolic complications, may influence fetoplacental growth and metabolism. They may also represent a crucial first step towards marker identification for MHO pregnancy and underscore the importance of alternative care pathways when obesity is present but metabolic comorbidities are absent.