Evaluation of Methods for Fetal Weight Estimates Using Ultrsound Formula at Term

Park, Mi Hae; Kim, Kyung Jin; Yang, Yun Seok; Hwang, In Tak; Jung, Ji Hak; Park, Jun Sook

Abstract

A total of 150women with singleton pregnancies who were delivered between 37 and 42weeks gestation had ultrasound scans on elective cesarean section day. The biparietal diameter(BPD), head circumference(HC), abdominal circumference(AC) and femur length(FL) were measured in all cases. Equations of estimated fetal body weight(BWT) for Korean term fetuses using AC alone, BPD/AC, AC/FL, HC/AC/FL, BPD/AC/FL, BPD/HC/AC/FL were made by stepwise multiple regression analysis and were compared with foreign equations such as Campbell(AC), Shepard(BPD/AC), Hadlock I(AC/FL), Hadlock II(HC/AC/FL), Hadlock III(BPD/AC/FL), and Hadlock IV(BPD/HC/AC/FL). The results were as follows. 1. The equations of BWT by sonographic measurement were Equation1 (AC) logeBWT=6.105936+0.005957X(AC) (R=0.876) Equation2 (BPD,AC)logeBWT=6.53614548+0.00004963X(ACXBPD) (R=0.929) Equation3 (AC,FL) logeBWT=6.25336442+0.00751602X(FL)+0.00005155X(ACXFL) (R=0.950) Equation4(HC,AC,FL) logeBWT=6.39631346+0.00004823X(ACXFL)+0.00002023X(FLXHC) (R=0.953) Equation5(BPD,AC,FL) logeBWT=5.99934074+0.00871394X(BPD)+0.00005132X(ACXFL) (R=0.960) 2. When BPD, AC and FL were measured, the addition of HC didn,t affected to accuracy of EFW 3. The best results of all equations were obtained with our equation 5(Mean error=2.36gm, Mean absolute error=96.39gm, Mean deviation + SD(%)=0.07+0.37) and among foreign equations, the best results were with Hadlock III equation(Mean error=18.35gm, Mean absolute error=107.82gm, Mean deviation + SD(%)=-0.46+0.42) 4. The equations using AC/FL (our equation 3, Hadlock I) are more accurate than those using BPD/AC (our equatione 2, Shepard) when utilizing two parameters. Therefore, equation using AC/FL is recommended when the BPD is unobtainable at term or labor 5. The percentage of cases in which the EFW was within +5% and +200gm of the actual birth weight was highest at our equation 5 for 82% and 89%, Hadlock IV equation for 79%, 88%. 6. Our equations had relatively an equal tendency to under- and overestimate fetal weight, but foreign equations, especially Campbell and Hadlock II equations tended to underestimate. 7. Analysing according to actual birth weight, our all equations gave the most accurate estimates of fetal weigh for birth weight group between 3000-3499gm, but for birth weight group above 3500gm, that was not. At birthweight group above 3500gm, the equations depend on femur length are more accurate than the equations independ on fumr length.