The Hadlock groupĭeveloped at least seven regression models using different combinations of fetal parameters and found the mean deviation from actual birth weight to be a low 0.3 to 0.4% for all of their formulas but the standard deviations varied with the AC/HC being the least accurate at 9.1% compared with the AC/FL at ± 8.2%, BPD/AC/FL at ± 7.7%, HC/AC/FL at ± 7.6% and BPD/HC/AC/FL with a ± 7.5% standard deviation. Is not the most suitable for predicting a macrosomic baby. Have shown this to be difficult as the formulae best suited to identifying the under 1000 g fetus The Altman groupĪdvised the use of the EFW formula with lowest random error (standard deviation) across the weight ranges but literature reviews There is a choice of over 20 EFW formulae on current ultrasound systems with most of these formulae being over 25 years old. Estimating fetal weight (EFW) is an expected adjunct of the third trimester sonogram as clinical decisions to intervene in the timing of the delivery are often based on the ultrasound findings, especially with small or large for gestational age babies, and so any improvement in the reliability of EFW may help improve clinical outcomes. Compared with the physical examination of the pregnant uterus the most accurate method for assessing and tracking fetal size and growth is with the use of ultrasound imaging and measuring of the various fetal parameters. This ASUM policy statement on normal ultrasonic fetal measurements was released in 1991 then updated in 1996 and again in 2002.Īntenatal ultrasound has become one of the clinicians' most important tools for assessing fetal age, growth and wellbeing. “No formula for estimating fetal weight has achieved an accuracy which enables us to recommend its use”. The lowest random error in all weight groups was the Hadlock B formula incorporating the HC/AC/FL (7.7%).Ĭonclusion: Considering the possible problems of head moulding this study suggests the use of: Hadlock FP et al (1982) – Formula B – incorporating HC/AC/FL. For all formulae the highest random error occurred in the macrosomic group. Accuracy of each EFW formula changed with different weight ranges. Intra‐observer error: 1.1 to 1.9% depending on fetal parameter. Results: Inter‐observer error: 1.3 to 3.1%. Method: EFW of 121 pregnancies assessed within 7 days of birth by measuring the BPD, OFD, HC, AC, FL and comparing to actual birth weight. 2 To compare six of the most commonly used EFW formulae and analyse inter/intra formulae variations for different weight range. Objectives: 1 To assess inter/intra observer error for fetal parameter measurements with multiple observers. There are numerous EFW formula available and yet in Australia no one formula has been recommended for use due to the lack of clinical evidence as to their accuracy. Clinical decisions are often based on the results of third trimester sonograms, particularly with small or large babies and so accuracy of estimating fetal weight (EFW) is essential.