Intrapartum prediction of birth weight using maternal anthropometric measurements and ultrasound scan

Abstract

This prospective study was conducted at Federal Medical Centre, Owo, Nigeria, between April 1st and 31st of July, 2013 to predict birth weight in labour using four clinical methods and ultrasound scan independently and comparatively to determine which is closest to the actual birth weight. The four clinical methods are Ojwang's formula, Johnson's formula, 5% of maternal weight and 10% of maternal body mass index. A total of 100 women who fulfilled the inclusion criteria had their foetal weight estimated using the methods. Accuracy of the prediction was determined by mean weight difference, percentage error and proportion of estimates within 10% of actual birth weight.Tests of significant difference were done and the level of significance was set at 0.05.Correlation and regression analyses were carried out.Of the five methods used, ultrasound scan estimation had the highest correlation coefficient of 0.681(P<0.001) followed by Ojwang's rule with correlation coefficient of 0.675(P<0.001). The prediction using Johnson's method performed next to Ojwang's rule with correlation coefficient of 0.629(P<0.001).The methods using 5% maternal weight and 10% maternal BMI had correlation coefficients of 0.312(P<0.001) and 0.220(P<0.001) respectively. It was then concluded that there is positive significant correlation between the methods used and actual birth weight. The method using 10% maternal BMI is the least reliable while the ultrasound scan estimate was the most reliable. Ojwang's rule estimation performed next to ultrasound and should be considered first in settings where ultrasound machine or the expertise to use the machine is lacking.

Keywords: Birth weight, Foetal weight, Ultrasonography, Pregnancy, Delivery, Prospective studies