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Infant weight gain patterns affect later BMI differently in twins and singletons, highlighting the need for birth type–specific growth monitoring.  

According to this pediatric study published in June 2025 in the issue of Journal of Pediatrics, the investigators examined the association between infant weight trajectory characteristics and childhood body mass index (BMI) in twins compared with singletons.   

They used data from the PROMISE study, a United States (US)-based electronic health record (EHR) of pregnant women born and their children born between 2004–2020, to compare 227 male and 250 female twins with 13,952 male and 13,500 female singletons, along with 2,270 male and 2,500 female singletons matched by gestational age (GA) and sex. The Jenss model was applied to estimate infant weight trajectories from 0 to 24 months, and linear regression was used to assess links between these growth characteristics and BMIz-scores (BMIz) at 3 and 5 years.  

The results showed that in twins, only late infancy weight gain (∼12–24 months) was positively linked to BMIz at ages 3 and 5, with a more pronounced effect in females than males. In contrast, among singletons, BMIz at both time points was associated with starting weight, early infancy gain (∼0–6 months), mid-infancy gain (∼6–12 months), and late infancy gain (∼12–24 months). Findings in GA-matched singletons reflected those observed in the overall singleton population.  

Investigators concluded that infant weight gain patterns influencing childhood BMIz differed between twins and singletons, with only late infancy gain linked to BMIz in twins. 

Source: jpeds.com/article/S0022-3476(25)00227-6/abstract