Maternal metabolic determinants of accelerated infant weight gain in early life: assessing the combined effects of gestational diabetes and pre-pregnancy overweight

Maternal overweight and GDM increase the risk of fetal growth, but the effect of their individual or combined exposure on infant growth trajectory remains unclear. Clarifying whether these exposures will lead to sustained or time-limited growth patterns is essential for developing tailored, time-sensitive early childhood monitoring strategies. Methods We analyzed a population-based cohort of 19 712 mother-infant pairs from Jiangsu Province (2024) using longitudinal data. Infant weight was measured at birth, 1, 3, and 6 months. Linear mixed effects models were employed to examine the independent and joint associations of maternal overweight and GDM with infant weight for age z-scores (WAZ), examining how the associations changed with infant age. Results Maternal overweight showed a strong, persistent association with higher infant WAZ ( β  = 0.160, 95% CI : 0.130–0.191), slightly strengthening with age. In contrast, GDM alone had only a modest initial effect ( β  = 0.065, 95% CI : 0.031–0.100) that significantly attenuated over time (interaction β = −0.008, P  = 0.006). The combined exposure yielded the highest initial beta coefficient ( β  = 0.217, 95% CI : 0.175–0.259) but the most rapid attenuation (interaction β = −0.017, P  < 0.001). Adjusted mean WAZ at 6 months was highest in the combined exposure. Conclusions Different growth patterns were found in this study: maternal overweight has a sustained effect, while GDM’s influence is time-limited. The combined exposure presents peak early risk that moderates over time. These findings highlight the necessity of developing targeted monitoring protocols and implement risk stratification and personalized interventions based on maternal metabolic profiles.