New weight estimation formula for macrosomic fetuses

Abstract

Objective To develop a new formula to estimate macrosomia weight and compared with published 25 formulas.Methods 1153 fetuses including 239 macrosomia within one week of delivery were considered.Two-dimensional ultrasound measurements of the fetal biparietal diameter (BPD),head circumference (HC),abdominal circumference (AC) and femur length (FL) were performed and recorded by experienced sonographers.The birth weight were measured after the babies born.The formula finding group,1034 fetuses including 914 fetuses weighting less than 4000g and 120 macrosomia,were utilized to generate an overall regression formula by stepwise linear regression.120 macrosomia were used to established the formula for estimating macrosomic weight.As the training group,other 119 macrosomia were used to test the new formula and compared with other 25 existing formulas.Results The new formula for whole weight was:lgBW =0.180 (HC) + 0.00628 (AC) - 0.00318 (HC)2 + 0.00173 (AC) (FL) +0.0000430(BPD)(HC)2.The new formula for macromia was:lgBW =0.730(BPD) -0.0375 (BPD)2 +0.000264(AC) (FL).The new method gave ( - 87.89 ± 230.95)g of estimation error and (4.4 ± 3.9) ％ of absolute percentage error,while the best existing formula provided (115.61± 345.09)g and (6.8 ± 5.4)％.With the new method,89.1％ of estimates fell within ± 10％ of the actual birth weight,while the best existing formula gave 75.6％.Conclusions The new formula was based on typical Chinese Han women,the error was lower and more suitable than those developed formulas for Chinese populations,especially for macrosomia fetuses. Key words: Ultrasonography, prenatal; Fetal macrosomia; Fetal weight