A Prospective Study on Comparison of Fetal Weight Estimation by Clinical Methods and Ultrasound and its Correlation with True Birth Weight in Term Pregnancies

Abstract

Background: Estimation of fetal weight is at most important in effective managing of obstetric labour. Ultrasound is a standard technique to measure the weight but there is scarcity of ultrasonography at remote areas. In such situations clinical techniques can be considered for fetal weight calculation. Our study has compared both clinical methods and ultrasonography (USG) and to correlate with true weight at birth. Objective: To compare the fetal weight estimation by clinical methods and ultrasonographic method and its comparison with true birth weight in pregnancy at term. Material and Methods: A diagnostic study (Longitudinal study) was carried out at the Obstetrics and Gynaecology Department at tertiary care hospital to compare the precision of clinical and USG estimation of weight of the fetus with actual birth weight at term. One hundred pregnant women satisfying the criteria were considered and consent for the study were enlisted. Both USG and clinical methods were used. The fetal weight calculated by the above three methods was compared with true birth weight of the baby. Analysis of the precision of the various methods was done. Results: In our study population, the mean age was 25.29±4.45. The average absolute error by EFW (estimated fetal weight)-USG method was least, 117.81g. Among the clinical methods the average absolute error by EFW-Dare's was least i.e. 145.40g. The Correlation Co-efficient was highest with USG method (0.80) of estimation of fetal weight. Among clinical methods, Johnson's formula had highest R Value of 0.79 followed by Dare's formula at 0.76. The EFW using both Dare's formula and Johnson's formula had an excellent predictive validity in predicting actual weight. The EFW using Johnson's formula had sensitivity of 76.06% and Dare's formula had sensitivity of 73.24% in predicting actual weight. The EFW using USG method had highest sensitivity of 80.28%. It was seen in this study that clinical methods can reliably estimate EFW and can be used in settings where USG is not available. Conclusion: Estimation of fetal weight by clinical techniques has a significant role in obstetric labour and delivery. The clinical methods are easy and cost effective and applicable universally in predicting fetal weight. They can be used even by midwives and in remote areas where Ultrasonography is not readily available. It can be used as an integral part in the management of obstetric labour and delivery in remote primary health centres.

Keywords

• estimated fetal birth weight
• johnson's formula
• dare's formula
• hadlock's formula
• ultrasonography