First‐Trimester Crown‐Rump Length and Large for Gestational Age Newborns: What Correlation?

OBJECTIVE: To evaluate whether crown-rump length (CRL) measured at 11-14 weeks is associated with the risk of large-for-gestational-age (LGA) neonates in uncomplicated pregnancies. METHODS: This prospective study included 333 singleton pregnancies undergoing first-trimester ultrasound screening. CRL was measured according to standardized criteria, and gestational age was confirmed or reassigned based on CRL when discrepancies with last menstrual period exceeded 7 days. The primary outcome was the occurrence of LGA neonates, defined according to INTERGROWTH-21st standards. Multivariate regression and receiver operating characteristic (ROC) curve analyses were performed to assess the predictive value of CRL. RESULTS: CRL was significantly associated with the risk of LGA neonates. ROC curve analysis demonstrated a modest discriminative performance, with an area under the curve (AUC) of 0.665 (95% CI: 0.547-0.784). The optimal CRL cut-off showed a sensitivity of 63.6% and specificity of 69.3%, with a high negative predictive value (96.4%). CONCLUSIONS: First-trimester CRL is associated with fetal overgrowth but shows limited predictive accuracy when used alone. Its clinical utility may lie in contributing to combined predictive models rather than serving as a standalone screening tool.