Transcerebellar Diameter/Abdominal Circumference Ratio in Normal and Asymmetric Growth Restricted Fetuses: A Cross-sectional Analysis in a Tertiary Care Hospital

Abstract

Assessment of correct gestational age (GA) is vital in the management and prognosis of any pregnancy. The cerebellar size tends to remain unaffected or minimally affected in mild and moderate growth restriction Measurement of fetal transcerebellar diameter is a marker for estimation of GA. In government tertiary care centers, there are a lot of patients who would visit for the first ultrasound in the third trimester wherein there is a wide variation in calculation of GA as per ultrasound parameters. So to assess correct GA and diagnose asymmetric intrauterine growth restriction (IUGR), TCD/AC ratio can be included in routine antenatal scan apart from other parameters used. To evaluate the ratio between transcerebellar diameter (TCD) and abdominal circumference (AC) as a GA independent parameter in this study population in second and third trimester and diagnose asymmetric IUGR of fetuses based on it. This was a cross-sectional study where TCDs and AC of fetuses of 250 pregnancies between 16 and 40 weeks with single fetus were measured and TCD/AC ratios were calculated. In 242 normal fetuses, the ratio was 0.138 (±0.02) with a standard deviation of 0.010 irrespective of the GA. In eight fetuses in the present study the ratio was more than two standard deviations which indicate asymmetric IUGR. TCD/AC ratio is a reliable GA independent marker to assess growth of the fetuses and for near accurate diagnosis of asymmetric IUGR. The limitation of this study is the short sample size for IUGR fetuses.