Head circumference as an early predictor of fetal death in fetuses with increased nuchal translucency: evidence from a multicenter cohort study.

Objectives: To assess the value of early gestational head circumference (HC) for predicting subsequent fetal death in women whose fetuses had increased nuchal translucency (NT).

Methods: Gestational age-specific NT and HC Z scores were calculated. The threshold for NT was confirmed by comparing the difference in HC predictive value for fetal death (including early fetal death [12-19 weeks] and stillbirth [≥ 20 weeks]) between NT groups (normal or increased NT). Thresholds for HC prediction of fetal death in fetuses with increased NT were confirmed, with corresponding sensitivity and specificity. The performance and clinical value of the model were evaluated. Multiple imputation method was conducted to assess the robustness of the results.

Results: A total of 16,436 women and their fetuses were included in the analysis. Fetal HC was lower in fetal deaths than in live births (P < 0.005). The 80th percentile was a preferred threshold for increased NT. The difference in HC between live and dead fetuses persisted in fetuses with NT > 80th percentile (median of HC Z score: - 0.66 vs. 0.34, P < 0.001), but not in those with NT ≤ 80th percentile. The HC Z score was valuable for predicting fetal death in fetuses with increased NT, with a sensitivity of 74% and specificity of 76%. The prediction was useful for early fetal death, not stillbirth. Internal validation showed that the model has good predictive performance and clinical utility. Multiply imputation analysis shows that the association of low HC with fetal death and its predictive value were weakened.

Conclusions: The early gestational age-specific HC Z score was associated with fetal death, particularly early fetal death, in fetuses with NT above the 80th percentile. Definitive validation through large-scale cohorts with protocol-based routine HC measurements is warranted before considering clinical application.