Background: Among the most crucial choices made in prenatal care is the calculation of gestational age [GA]. This is the foundation for managing difficulties and having babies at the right time.
Aim of work: Utilizing the fetal maximal transverse cerebellar diameter in contrast to biparietal diameter and femur length, gestational age may be determined during the third trimester.
Subjects & methods: 159 pregnant women carrying a singleton between the ages of twenty-eight and thirty-six weeks participated in this prospective cross-sectional research at Damietta's Al-Azhar University Hospital's Department of Obstetrics and Gynecology.
Results: In our study, the mean values were as follows: The biparietal diameter [BPD] was 81.86 ± 3.08 millimeters, the head circumference [HC] was 29.96 ± 1.95 millimeters, the abdominal circumference [AC] was 30.99 ± 1.57 centimeters, the femur length [FL] was 6.29 ± 0.57 centimeters, and the transverse cerebellar diameter [TCD] was 3.86 ± 0.23 centimeters. TCD provided the most accurate assessment of gestational age [83.6%], followed by FL [67.9%] and BPD [47.2%], while AC [37.7%] and HC [35.2%] were the least accurate. The mean estimated fetal weight was 3091.7 ± 267.2 grams. Additionally, BPD, HC, AC, FL, and TCD had sensitivities of 47.0%, 35.0%, 37.0%, 67.0%, and 83.0% and specificities of 77.5%, 85.0%, 82.5%, 75.0%, and 80.0%, respectively, all showing statistically significant predictive value for gestational age.
Conclusion: Our study demonstrated that fetal maximum TCD is a highly reliable parameter for third-trimester gestational age estimation, accurately predicting GA in 83.6% of cases—outperforming other biometric measures such as femur length [67.9%], biparietal diameter [47.2%], head circumference [35.2%], and abdominal circumference [37.7%]. The mean estimated fetal weight was 3091.7 ± 267.2 grams. Although promising, our findings are limited by a small, single-center sample and the absence of first-trimester CRL comparison; hence, larger, multicenter studies are recommended to further validate TCD's utility in prenatal care.