Selection of appropriate ultrasound methods for the estimation of fetal weight

Abstract

Many methods for fetal weight estimation have been proposed. Earlier formulae were derived solely by regression analysis but more recently formulae based on physical models have been developed. Some of these formulae are lengthy and difficult to use. The main purpose of this study was to evaluate a concise area based formula developed several years ago against popular and recently published formulae. Data from 388 patients over a 5 year period were collected from clinically required ultrasound scans performed within 10 days of delivery. Four of the seven formulae evaluated proved to be equally accurate over a broad range of birthweights (mean absolute deviations 245-249 g), including the area based formula and a circumference based formula derived from it. On the grounds of the number of terms, the precision of coefficients, the physical meaning and the greater accuracy of individual area measurements compared with those derived from circumference, the area based formula should be the method of choice.

Accuracy of sonographic estimation of fetal weight before induction of labor in diabetic pregnancies and pregnancies with suspected fetal macrosomia

“…Several formulas based on different sonographic measurements of fetal organs have been developed to estimate fetal weight with varying accuracy and precision [17,19]. For all methods, the accuracy of the fetal weight estimation decreases with increasing birth weight [5,8,10]. Hadlock's formula has a mean absolute error of 13% for infants weighing more than 4,500 gr, and only 8% for nonmacrosomic infants [1].…”

An informative probability model enhancing real time echobiometry to improve fetal weight estimation accuracy

“…Many recent attempts have been made to reduce the estimation error on lower and higher FWs, where the clinical interest is of course focused. In general, clinicians distinguish these two critical intervals of weight from an intermediate one that typically ranges from 2,500 to 4,000 g [16,20,23]. Almost all models for EFW exhibit a worsening of accuracy in critical weight classes (below 2,500 g and above 4,000 g) where lower/higher weights are usually over/under-estimated [13,16,29].…”

“…In general, clinicians distinguish these two critical intervals of weight from an intermediate one that typically ranges from 2,500 to 4,000 g [16,20,23]. Almost all models for EFW exhibit a worsening of accuracy in critical weight classes (below 2,500 g and above 4,000 g) where lower/higher weights are usually over/under-estimated [13,16,29]. Most mathematical models are derived from statistical regressions and account nonlinearly for ultrasound measurements by fitting experimental data.…”

“…In the last 30 years, many methods have been developed to improve EFW accuracy, most based on formulae derived by regression analysis [3,16,22,23,25,27,33,35,36,38,41,44], or on physical models [2,14,17,29]. Artificial neural networks (ANNs) and volumetric methods based on three-dimensional (3D) ultrasonography were also recently proposed [11,20,40].…”

“…Though many attempts have been made to reduce estimation errors by means of models specialized in particular ranges of FW or GA [16,23,36], or derived from sophisticated 3D and ANN methods [11,40], it has not proven possible to significantly reduce the error, because it is presumably due to many different unpredictable factors (human, environmental, instrumental, technological, etc.) associated with digital processing of echobiometric values [17].…”