A prediction nomogram for faltering catch-up growth in full-term small-for-gestational-age infants: a retrospective...

Catch-up growth (CUG) before two years of age in small-for-gestational-age (SGA) infants is a key predictor of adult short stature. We aimed to establish and temporally validate a prediction nomogram for faltering CUG (FCUG) in full-term SGA infants before two years of age.

We conducted a retrospective cohort study of full-term SGA infants at West China Second University Hospital, with cohorts defined as: development (January 1996-December 2019) and temporal validation (January 2020-July 2023). Full-term SGA infants, defined by birth weight or length below 10th percentile per INTERGROWTH-21st standards (n = 1,185 in development; n = 294 in validation). FCUG was defined as failure to increase length-for-age Z score by ≥0.67 above birth Z score by 24 months. Sex, birth weight Z, birth length Z and target height Z scores were entered into a multivariable logistic model. Discrimination (AUC, sensitivity, specificity), calibration (Hosmer-Lemeshow, calibration plot), internal (1,000 bootstrap resamples) and temporal (2020-2023 cohort) validations were performed.

In the development cohort, 280 of 1,185 (23.6%) of SGA infants experienced FCUG before age two, compared with 60 of 294 (20.4%) in the temporal validation cohort. In multivariable logistic regression analyses, male sex, lower birth length Z score, lower birth weight Z score, and lower target height Z score were all significantly associated with FCUG (all p < 0.05). These four predictors were incorporated into a nomogram. In the development cohort, the model demonstrated excellent discrimination (AUC = 0.810, 95% CI: 0.785-0.835) with a sensitivity of 74% and specificity of 74% at the optimal cut-off. Bootstrap validation (1,000 resamples) confirmed a stable AUC of 0.810. When applied to the temporal cohort, the nomogram achieved an AUC of 0.784 (95% CI: 0.730-0.838), with sensitivity of 93% and specificity of 56%.

We have developed and temporally validated a clinically applicable nomogram that reliably identifies full-term SGA infants at high risk of failing to achieve catch-up growth by age two. With robust discrimination and calibration, this tool can support early risk stratification and guide targeted nutritional or developmental interventions.