Association of Maternal Overweight/Obesity Metabolic Phenotypes With Longitudinal Foetal Anthropometric Measurements

AIMS: To examine the associations between early-pregnancy maternal overweight/obesity metabolic phenotypes and foetal anthropometric measurements and assess mediation by gestational diabetes mellitus (GDM) and pregnancy-induced hypertension (PIH). METHODS: This study included 7633 pregnant women from a Chinese prospective cohort. Participants in early pregnancy were classified as metabolically healthy normal weight (MHNW), metabolically unhealthy normal weight (MUNW), metabolically healthy overweight/obesity (MHO) and metabolically unhealthy overweight/obesity (MUO). Generalised linear mixed models evaluated associations with repeated ultrasound measures for participants with at least one scan between 22 and 36 weeks. Mediation analyses evaluated GDM and PIH effects. RESULTS: Compared to MHNW, both MHO and MUO were associated with higher estimated foetal weight (EFW) and abdominal circumference (AC) Z-scores mainly during 28-36 weeks, as well as an elevated risk of foetal EFW and AC overgrowth. Furthermore, the MUO increased the risk of head circumference (HC) undergrowth (OR = 1.22, 95% CI: 1.00-1.48). Conversely, the MUNW was associated with lower foetal HC Z-scores (β = -0.05, 95% CI: -0.10 to 0.00). In addition, GDM mediated the association between MUNW and reduced foetal HC Z-scores at 28-32 and 33-36 weeks, with mediation proportions of 11.2% and 16.1%, respectively. CONCLUSIONS: Early-pregnancy maternal overweight/obesity metabolic phenotypes are associated with foetal growth. MHO and MUO increase EFW and AC overgrowth risks, while MUO also raises HC undergrowth risk. Conversely, MUNW is associated with a reduced HC Z-score, a pathway mediated by GDM. These findings highlight that the joint assessment of body mass index and metabolic health is vital for targeted maternal care.