The accuracy of trans cerebellar diameter in assessing gestational age in the second and third trimesters of pregnancy

Background and objective: Accurate estimation of the fetal gestational age is the cornerstone for the management of all pregnancies. This study aims to assess the accuracy of Trans cerebellar diameter in comparison with the other previously established fetal biometric parameters in the second and third trimesters. Methods: This is a prospective study conducted on 237 pregnant women who attended Erbil Maternity Teaching Hospital and a private clinic from January 2021 to July 2022. The ultrasound of selected cases was performed on GE Voluson E6 and E8 ultrasound machines with a 3.5 MHz probe sector transducer. Trans cerebellar diameter measurement was obtained by placing the electronic calibers from the outer portion of the proximal end of the cerebellum to the inner portion of the distal margin. Biparietal diameter, femoral length, head circumference, and abdominal circumference were measured using the standard technique by Hadlock tables. Data were tabulated and all the statistical analyses were done using SPSS version 26. Results: The mean trans cerebellar diameter during different gestational ages was 19.95 (±1.2) mm between 18-22 weeks gestation, 25.45 (±1.7) mm between 23-28 weeks gestation, 29.79 (±1.15) mm between 29-32 weeks gestation, 34.29 (± 1.13) mm between 33-36 weeks gestation and 36.79 (±1.7) mm above 37 weeks gestation respectively. Differences between the estimated gestational age and the gestational age assessed by trans cerebellar diameter ranged from -7 to 6 days irrespective of the gestational age. Conclusion: Even in the third trimester trans cerebellar diameter is a fairly accurate and better predictor of gestational age in comparison to other ultrasound parameters such as biparietal diameter, head circumference, abdominal circumference, and femoral length.