Significance of Foetal Transcerebellar Diameter in Foetal Biometry: A Pilot Study.

Abstract

The most important parameter needed for appropriate management of pregnant women is accurate Gestational Age (GA). Routine sonographic estimation of GA by using Biparietal Diameter (BPD), Femur Length (FL), Abdominal Circumference (AC) and Head Circumference (HC) assumed important role in management of pregnancy. However, these parameters have limitations. BPD and HC are not reliable in case of moulding of foetal head in third trimester. Similarly, femur length is shortened in cases of achondroplasia. Transcerebellar Diameter (TCD) was developed as an alternative parameter of foetal brain growth and for estimation of GA. To evaluate accuracy of predicting GA using Foetal Transcerebellar Diameter (TCD) and to compare between TCD and other existing parameters in evaluating GA in 15 to 40 weeks of gestation. A prospective study was carried out in 100 pregnant women between 15 to 40 weeks of gestation, who came for routine antenatal sonography. Transcerebellar diameter was measured along with routine parameters. Subjects were divided into two groups based on GA (15-28 and 29-40 weeks). Gestational age using TCD and other parameters was calculated and compared with gestational age based on Last Menstrual Period (LMP). Correlation between the GA by LMP with GA by other ultrasound parameters was done by using Karl Pearson's Correlation(r). In 15-28 weeks, all parameters had nearly equal r-values. Among all parameters, TCD revealed highest correlation with value of 0.997. In 29-40 weeks, there was considerable difference in r-values. An r-value of 0.982 was noted, when the GA by TCD and LMP was compared, r-value of which is more than the other parameters. The least correlation was seen with BPD, r=0.951. The second most accurate correlation was seen with the FL with r-value of 0.981. TCD is an accurate parameter in estimation of gestational age in second and third trimesters as its values are in close relation with that of GA by LMP. It is also better predictor of the gestational age when compared to other parameters especially in third trimester.