Normal Standard TCD/AC Ratio for the Evaluation of Intrauterine Growth Restriction in Singleton Fetuses

Background: Intrauterine growth restriction is associated with increased fetal mortality rate, and its early detection is important for determining delivery timing and planning neonatal care. This study aimed to examine the usefulness of the fetal transverse cerebellar diameter (TCD) to abdominal circumference (AC) ratio in fetal growth evaluation that can predict intrauterine growth restriction and propose a reference value for normal Korean fetuses. Methods: This study included a total of 1011 fetuses between 19 and 34 weeks of gestation from January 2021 to December 2022. A simple regression analysis was conducted to determine the relationship between TCD and AC and gestational age, and the normal mean values and percentiles of the TCD/AC ratio by gestational age were calculated. Results: TCD and AC correlated strongly with gestational age, increasing along with gestational age. The TCD/AC ratio in normal fetuses between 19 and 34 weeks of gestation was 13.26, with a 95th percentile of 14.39. Conclusions: The TCD/AC ratio can be utilized as a useful variable to predict intrauterine growth restriction when evaluating the growth of Korean fetuses. Furthermore, close observation is required when the TCD/AC ratio exceeds 14.39, allowing for early prediction and management of intrauterine growth restriction.