Accuracy of Ultrasonographic Transcerebellar Diameter for Gestational Age Estimation: A Systematic Review and Meta‐Analysis

BACKGROUND: Accurate estimation of gestational age (GA) is essential in prenatal care and assessment of perinatal outcomes. Standard dating methods such as last menstrual period (LMP) or conventional ultrasound biometry may be limited by fetal position, late antenatal booking, or intrauterine growth restriction (IUGR). The transcerebellar diameter (TCD) has been proposed as a robust alternative for GA estimation, particularly in late gestation or when other methods are unreliable. This study systematically evaluates the accuracy of TCD-based GA estimation in the second and third trimesters in both normal and IUGR pregnancies. METHODOLOGY: We conducted a systematic review and meta-analysis in accordance with the PRISMA guidelines. Databases including PubMed, Scopus, and ScienceDirect were searched from inception through July 2025 for studies assessing the correlation between TCD and GA. Google Scholar was also searched for relevant articles. Inclusion criteria were original studies reporting correlation coefficients between TCD and GA determined by LMP or first-trimester ultrasound. Data extraction and risk of bias assessments were performed independently by two reviewers. Meta-analyses were conducted using random-effects models in R. RESULTS: In this meta-analysis of 47 studies comprising 24 825 participants, the pooled correlation between TCD and GA was consistently strong. In the third trimester, r = 0.94 (95% CI: 0.89-0.97); in the second trimester, r = 0.93 (95% CI: 0.87-0.96); and across the combined second or third trimester, r = 0.98 (95% CI: 0.97-0.98). This was comparable to other fetal biometric parameters: BPD (r = 0.97), HC (r = 0.97), FL (r = 0.98), and AC (r = 0.97), with no statistically significant differences in pairwise comparisons (p > 0.05). In pregnancies affected by IUGR, TCD correlation with GA (r = 0.94, 95% CI: 0.89-0.97) was significantly higher than that of other biometric measures: BPD (r = 0.69), HC (r = 0.72), FL (r = 0.80), and AC (r = 0.78) (p < 0.001). CONCLUSION: TCD is a reliable and highly reproducible parameter for gestational age estimation, with strong correlations in late pregnancy. In pregnancies affected by IUGR, TCD was superior to other parameters. Its short learning curve and standardized methodology support its clinical utility as a complementary or primary tool for GA assessment, particularly in late pregnancy or when standard methods are limited.