Evaluation of Third Trimester Gestational Age Using Fetal Maximum Transverse Cerebellar Diameter

Background; Gestational age (GA) estimation is one of the most important decisions during antenatal care. It is the basis for the appropriate timing of deliveries and management of complications. Aim of work; to determine gestational age at the third trimester by using fetal maximum transverse cerebellar diameter in comparison with biparietal diameter and femur length. Subjects & methods; this prospective cross-sectional study was conducted at the Department of Obstetrics and Gynecology at Al-Azhar University Hospital, Damietta, on 159 singleton pregnant women at their 28-36 weeks of gestation. Result; mean (BPD) of the studied group was 81.86±3.08 mm, mean (HC) was 29.96±1.95 mm, mean (AC) was 30.99±1.57 cm, mean (FL) was 6.29±0.57 cm, mean (TCD) was 3.86±0.23 cm. The Transverse cerebellar diameter (TCD) gave the most correct assessment of gestational age (83.6%), followed by the (FL) (67.9%), The (BPD) correctly assessed (47.2%) of gestational age and the least accurate was the (AC) and (HC) that correctly assessed (37.7% and 35.2%, respectively) of gestational age. Mean estimated fetal weight of the studied group was 3091.7±267.2 gram. Conclusion; Our findings demonstrated that (TCD) is a highly reliable measure for assessing gestational age, accurately estimating it in 83.6% of cases, surpassing (FL) (67.9%) and BPD (47.2%). In contrast, abdominal circumference (AC) and head circumference (HC) showed limited predictive accuracy at 37.7% and 35.2%, respectively. The study also provided valuable normative data for ultrasound parameters, including mean (TCD) (3.86±0.23 cm), (BPD) (81.86±3.08 mm), and (FL) (6.29±0.57 cm), reinforcing the utility of (TCD) as a precise tool for third-trimester gestational assessment.