Distinct body mass index trajectories throughout childhood in girls with early puberty

Abstract Background Early pubertal development in girls has been associated with increased adiposity in childhood. However, longitudinal body mass index (BMI) trajectories preceding the diagnosis of precocious puberty (PP) or premature adrenarche (PA) are less well described. We hypothesized that distinct BMI trajectories leading to overweight or obesity could be identified already in infancy and early childhood in these girls. Methods In this nationwide register-based study, longitudinal data from Danish health registries were used to examine BMI trajectories from birth to 10 years of age. Girls diagnosed with PP or PA were analyzed separately using latent class trajectory analysis. Results In both populations with either PP or PA, mean BMI levels were in the upper normal range from infancy, followed by early adiposity rebound and progression into the overweight range from mid-childhood. Three distinct BMI trajectory classes were identified in girls with PP and PA, characterized by persistently higher BMI, early adiposity rebound, or lower birth weight followed by rapid postnatal weight gain. Conclusions Longitudinal BMI trajectories preceding the diagnosis of PP and PA showed heterogeneity in early-life growth patterns. These findings provide additional context for understanding how early-life adiposity and weight gain relate to pubertal timing and progression in girls. Impact Girls with precocious puberty or premature adrenarche exhibit distinct BMI trajectories from infancy throughout childhood, characterized by early adiposity rebound and accelerated weight gain preceding pubertal onset. This study adds a longitudinal perspective by identifying heterogeneous early-life BMI trajectories, demonstrating that differences in growth patterns can be detected already in early childhood, rather than relying on single BMI measurements later in childhood. These findings highlight early childhood as a critical window during which modifiable growth patterns may influence pubertal timing and progression, with implications for early identification and prevention strategies.