Association Between Maternal Pre-Pregnancy Body Mass Index and Growth Delay in Korean Children Aged 18–36 Months: A Population-Based Study

<b>Background:</b> Maternal pre-pregnancy body mass index (BMI) has been linked to childhood growth. However, its effects on growth delay at different early life stages are not well understood. This study aimed to evaluate the relationship between maternal pre-pregnancy BMI and growth delay in Korean children, using data from the National Health Screening Program for Infants and Children. <b>Methods</b>: Data from 258,367 children born between 2014 and 2021 who underwent health screenings at both 18-24 and 30-36 months of age were analyzed. Maternal BMI within three years before childbirth was classified into five categories: <18.5, 18.5-22.9 (reference), 23-24.9, 25-29.9, and ≥30 kg/m². Growth delay was defined as measurements below the 10th percentile for height, weight, and head circumference. Adjusted relative risks (RRs) were estimated using regression models controlling for maternal age, comorbidities, and perinatal factors. <b>Results</b>: An increased risk of height growth delay was observed with higher maternal BMI, and this association persisted at both 18-24 and 30-36 months. In contrast, maternal underweight was not significantly associated with a height delay. Low maternal BMI was associated with underweight status in children. Head circumference growth delay was linked to both high and low maternal BMI; children of mothers outside the normal BMI range had an increased risk. <b>Conclusions</b>: Maternal pre-pregnancy obesity and underweight were associated with growth delays in height, weight, and head circumference in children up to 36 months of age. These findings underscore the importance of individualized weight management before pregnancy.