Gestational age estimation using transcerebellar diameter with grading of fetal cerebellum and evaluation of TCD/AC (Transcerebellar diameter/abdominal circumference) ratio as a gestational age independent parameter

Objective : To prospectively evaluate the accuracy of transcerebellar diameter (TCD) in estimation of gestational age (GA), to study foetal cerebellar appearance on USG and its grading and to evaluate the ratio between transcerebellar diameter and abdominal circumference (AC) as a gestational age independent parameter. Material and Method : In 100 pregnant women between 16-40 weeks of gestation TCD, AC and TCD/AC ratio were recorded followed by the study of their predictive accuracy for GA. Simultaneously the US appearance of the cerebella were noted and grouped into 'three' grades. Result and Conclusion: TCD showed close correlation with gestational age and TCD/AC ratio was fairly constant irrespective of the gestational age and almost all fetuseswith TCD/AC ratio exceeding 2SD were reported to have asymmeteric intra uterine growth retardation (IUGR). In our study, cerebella in 46 percent, 25 percent and 29 percent cases were classified as grade I, II and III respectively and a progressive changeof grade I to grade III was noted with advancing gestation.