الفهرس | Only 14 pages are availabe for public view |
Abstract Summary EFBW is needed especially when head measurement is impossible, because the fetal head is positioned low in the pelvic brim. A convenient method for estimating fetal body weight without head measurement was thus required. Isobe (2004) derived a formula from only thigh measurements using conventional two dimensional ultrasound. The derived formula was quite simple, involving only two thigh parameters without the need for head measurement. The aim of this study was to evaluate the accuracy of using only 2 thigh parameters ; Femur Length ( F L ) and Cross Sectional Area of the Thigh ( CSAT ) , together with the newly established Isobe’s formula for estimation of fetal body weight at third trimester, in comparison with the well established Hadlock formula. This prospective study was performed at Ain Shams University Maternity Hospital between August 2012 and February 2013. It included 105 pregnant ladies in their third trimester, who delivered by elective cesarean section in than 72 hours after having two dimensional ultrasound examinations. All cases participated in the study were subjected to: Verbal consent. Detailed history reviewing. Detailed clinical examination. Ultrasound examination. Elective cesarean section. All measurements were performed by an expert sonographer in the fetal ultrasound unit using a transabdominal ultrasound with 5.0 MHz convex probe (Medison SonoAce X6). Parameters like Bi-parietal diameter (BPD), Abdominal Circumference (AC), Femur length (FL) and Cross sectional area of thigh (CSAT) were measured respectively. The estimated fetal body weight was calculated twice as follow: 1- Using Hadlock’s formula, which had been calculated by the machine programmed software, using BPD, AC and FL. 2- Using Isobe’s formula, which had been calculated manually using FL and CSAT as follow: EFBW = 13 × (FL × √CSAT) + 39 (gm). N.B: FL by millimeter, CSAT by centimeter. The birth weight (BW) of the infant was measured immediately after delivery. This prospective study was analyzed and evaluated by comparing the results of EFBW using the previously illustrated newly established Isobe’s formula [using femur length (FL) and cross sectional area of the thigh (CSAT)] and already established commonly used Hadlock formula [using biparietal diameter (BPD), abdominal circumference (AC) and femur length (FL)] with actual birth weight. Actual birth weight was taken as the gold standard. Differences among estimated weights from the Isobe formula, Hadlock formula and the actual birth weight was assessed by a paired t test and corrected chi-squared test. The mean actual birth weight in included women was 3217.8 ± 573.03 g. Of the 105 included neonates, 88 (83.8%) had average birth weight [2500 – 4000 g], 10 (9.5%) had low birth weight [<2500 g], while 7 (6.7%) had large birth weight [> 4000 g]. There was a significant positive correlation between actual birth weight and each of EFW using Hadlock’s formula, EFW using Isobe’s formula. The highest correlation coefficient was with EFW using Isobe’s formula [r=0.924, p˂0.01], indicating the most significant association. The mean paired difference between EFW using Hadlock’s formula and actual birth weight was -100.07 ± 326.24 g [95% CI (-163.21 to -36.94 g); p=0.002]. The mean paired difference between EFW using Isobe’s formula and actual birth weight was 62.16 ± 230.37 g [95% CI (17.57 to 106.74 g); p=0.007]. The narrower 95% CI and the high p value for the Isobe’s formula when compared to Hadlock’s formula denote closer values of the estimated fetal weight to the actual birth weight using the former formula than the latter one.Of note, the mean paired difference was positive in Isobe formula (i.e. the error toward overestimation) while Hadlock formula has a negative mean for the paired difference (i.e. the error is toward underestimation). Among the average birth weight category, the mean paired difference was lower when Isobe’s formula rather than Hadlock’s formula was used [-36.46 ± 188.98 g vs. 90.15 ± 322.48g]. The difference was positive in Hadlock’s formulae [denoting an overestimating error] while negative in Isobe’s formula [denoting an underestimation error]. Among the low birth weight category, Isobe formula had mean paired difference markedly higher than that noticed among the average birth weight category, and it was noted that the Hadlock’s formula had negative mean paired difference while it was positive in average birth weight. In addition Hadlock’s formula had lower mean paired difference & tight range when compared to the Isobe’s formula [-85.4 ± 209.3g vs. -455.7 ± 200.26 g]. The mean was negative in both formulae [denoting an underestimating error]. Among the large birth weight category, Hadlock’s formula had mean paired differences markedly higher than that noticed among the average birth weight category, and it was noted that Isobe’s formula had positive and higher mean paired difference when compared to that of average birth weight. both Hadlock’s formula and had positive mean paired difference [489.7 ± 187.86 g vs. 177 ± 85.9 g]. The difference was positive in both formulas [denoting an overestimating error |