Objectives
The range and use of ultrasound fetal measurements have gradually been extended. Measurements have been combined to estimate fetal weight by mathematically based non-linear regression analysis or physically based volumetric methods. Fetal weight estimation is inaccurate, with poor sensitivity for prediction of fetal compromise. Several authors have shown the unacceptable level of intra- and interobserver variability in fetal measurement and the impact of errors on growth assessment. The aims of this study were to review the available methods and possible sources of inaccuracy.

Methods
Four databases were searched for studies comparing ultrasound estimated fetal weight (EFW) with birth weight. Studies meeting the inclusion criteria evaluated 11 different methods. Errors were graphically summarized.

Results
No consistently superior method has emerged. Volumetric methods provide some theoretical advantages. Random errors are large and must be reduced if clinical errors are to be avoided.

Conclusions
The accuracy of EFW is compromised by large intra- and interobserver variability. Efforts must be made to minimize this variability if EFW is to be clinically useful. This may be achieved through averaging of multiple measurements, improvements in image quality, uniform calibration of equipment, careful design and refinement of measurement methods, acknowledgment that there is a long learning curve, and regular audit of measurement quality. Further work to improve the universal validity and accuracy of fetal weight estimation formulae is also required. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.

https://obgyn.onlinelibrary.wiley.com/doi/pdf/10.1002/uog.1751

A systematic review of the ultrasound estimation of fetal weight

Defining normal and abnormal fetal growth: promises and challenges.

Objectives: To review the evidence of effectiveness of prenatal care for preventing low birth weight (LBW). Methods: We reviewed original research, systematic reviews, meta-analyses and commentaries for evidence of effectiveness of the three core components of prenatal care - risk assessment, health promotion and medical and psychosocial interventions - for preventing the two constituents of LBW: preterm birth and intrauterine growth restriction (IUGR). Results: Clinical risk assessment will fail to identify the majority of pregnancies at risk for preterm delivery or IUGR. While biophysical and biochemical modalities appear promising, their cost-effectiveness has not been demonstrated, nor can their routine use be recommended in the absence of effective interventions. Smoking cessation programs appear to be modestly effective. There is insufficient evidence to conclude a benefit for nutrition interventions, work counseling or preterm birth education. Only antenatal corticosteroid therapy has demonstrated ...

Preventing low birth weight: is prenatal care the answer?

Objective To introduce fractional limb volume as a new ultrasonographic parameter, validate reliability of fractional limb volume measurements, develop new birth weight prediction models, and examine their practical utility for estimating fetal weight during late pregnancy. Methods Healthy late-third-trimester fetuses were prospectively scanned by two- and three-dimensional ultrasonography within 4 days of delivery. Volume data sets were subsequently used to extract several standard ultrasonographic measurements. Fractional limb volumes of the upper arm and thigh were based on 50% of diaphyseal bone length. Intraclass correlation was used to analyze interobserver and intraobserver reliability of fractional limb volume measurements. Several weight prediction models were developed by linear regression analysis. New prediction models were prospectively compared with the Hadlock formula in 30 healthy late-third-trimester fetuses. Results One hundred fetuses were scanned at a mean +/- SD menstrual age of 39.2 +/- 1.2 weeks. Intraclass correlation indicated a significant degree of interobserver and intraobserver reliability for fractional thigh volume. Fractional thigh volume (r = 0.86), fractional upper arm volume (r = 0.83), abdominal circumference (r = 0.83), and midthigh circumference (r = 0.82) were most highly correlated with birth weight. The best prediction model (abdominal circumference and fractional thigh volume) gave weight estimates that deviated from actual birth weight by -0.025% +/- 7.8%. For late-third-trimester fetuses, the Hadlock model yielded errors of 9.0% +/- 9.0%. Prospective testing confirmed superior performance of the new prediction model, which gave accuracy of 2.3% +/- 6.6% (Hadlock method, 8.4% +/- 8.7%). It correctly predicted 20 of 30 birth weights to within 5% of actual weight. By comparison, the Hadlock model predicted only 6 of 30 birth weights to within 5% of actual weight. Conclusions A new birth weight prediction model, based on fractional thigh volume and abdominal circumference, is reliable during the late third trimester. It provides a means for including soft tissue evaluation for birth weight prediction. This rapid technique avoids technical limitations that currently hinder the practical implementation of three-dimensional ultrasonography for estimating birth weight.

Birth weight prediction by three-dimensional ultrasonography: fractional limb volume.

Prenatal diagnosis and management of congenital cystic adenomatoid malformation of the lung

Predicting birth weight by fetal upper-arm volume with use of three-dimensional ultrasonography

CCAML is a rare abnormality characterized by an overgrowth of terminal bronchioles. I The main feature on prenatal ultrasonography is an echogenic mass in the lung with cysts of varying size. Its prognosis depends on the hydropic change of the fetus and the content of lung hypoplasia. I Although the natural history of CCAML is still unknown, several reports have i:iescribed reduced size or even com· plete regression of CCAML before birth.24 CCAML type III was thought to have the gravest prognosis, and its spontaneous resolution was seen rarely.4 To our knowledge, only one such case has been reported in the literature.4 We describe two cases of CCAML type III diagnosed by ultrasonography at 22 and 25 weeks' gestation. Serial follow-up sono-

Bor-Lin Yao

Papers

Predicting birth weight by fetal upper-arm volume with use of three-dimensional ultrasonography

Complete intrauterine resolution of fetal congenital cystic adenomatoid malformation of the lung type III.