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

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.

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.

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%).

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.