Comparative Study of Clinical and Sonographic Estimation of Foetal Weight at Term

A cross sectional comparative study was conducted at Dhaka National Medical College, Dhaka from January to June 2012, to observe the accuracy of clinical and ultrasonographic estimation of foetal weight at term in our environment. Seventy five pregnant women who fulfilled the inclusion criteria had their foetal weight estimated independently using clinical and ultrasonographic methods. Accuracy was determined by percentage error, absolute percentage error and proportion of estimates within 10% of actual birth weight (birth weight fetus of +10%). Statistical analysis was done using the paired t-test, the Wilcoxon signed-rank test, and the chi-square test. The study sample had an actual average birth weight of 2989.60 ± 408.76 (range 2310-4000 gm). Overall, the clinical method overestimated birth-weight, while ultrasound underestimated it. The mean absolute percentage error of the clinical method was more than that of the sonographic method, and the number of estimates within 10% of actual birth weight for the clinical method (41.3%) was less than for the sonographic method (57.3%); the difference was not statistically significant. In the low birth-weight (<2,500 gm) group, the mean absolute percentage error of sonographic estimates were significantly smaller. Significantly more sonographic estimates (75%) were within 10% of actual birth-weight than those of the clinical method (0%). No statistically significant difference was observed in all the measures of accuracy for the normal birth-weight range of 2,500-<4,000 gm and in the macrosomic group (≥ 4,000 gm). Clinical estimation of birth-weight is as accurate as routine ultrasonographic estimation, except in low-birth-weight babies.