Sonographically estimated fetal weights: Accuracy and limitation

doi:10.1016/0002-9378(88)90425-5

American Journal of Obstetrics and Gynecology

Volume 159, Issue 5, November 1988, Pages 1118-1121

https://doi.org/10.1016/0002-9378(88)90425-5 Get rights and content

Abstract

To determine the accuracy of our ultrasonographically predicted birth weights we studied 1301 women delivered of infants within a week of an obstetric ultrasonogram to compare the ultrasonographically predicted birth weights with the actual birth weights. The fetuses varied from 700 to 5800 gm and were consecutive singleton fetuses in vertex presentations delivered at a single institution. Overall 74% of the infants had birth weights within 10% of the ultrasonographic estimates and 42% had birth weights within 5% of the ultrasonographic estimates. The presence of oligohydramnios or polyhydramnios made no difference in the percent errors. The sensitivity for identifying a fetus with macrosomia (birth weight > 4000 gm) with an estimated weight of ≥ 4000 gm was 65%. The specificity or percent of fetuses correctly identified ultrasonographically as not macrosomic was 90%. If fetuses predicted by ultrasonography to be > 3800 gm were included, the sensitivity for the prediction of macrosomia rises to 82% but the specificity would be 79%. There appears to be a fixed limitation to obtaining estimated fetal weights by ultrasonography, even in large series, because these data reaffirm the success and limitations of other methods used to estimate fetal weight previously reported in the literature.

References (13)

SL Warsof et al.
The estimation of fetal weight by computer-assisted analysis
Am J Obstet Gynecol
(1977)
MJ Shepard et al.
An evaluation of two equations for predicting fetal weight by ultrasound
Am J Obstet Gynecol
(1982)
FP Hadlock et al.
Estimation of fetal weight with the use of head, body, and femur measurements—a prospective study
Am J Obstet Gynecol
(1985)
KJ Dornan et al.
Fetal weight estimation by real-time ultrasound measurement of biparietal and transverse trunk diameter
Am J Obstet Gynecol
(1982)
LM Hill et al.
Use of femur length in estimation of fetal weight
Am J Obstet Gynecol
(1985)
CB Benson et al.
Sonographic determination of fetal weights in diabetic pregnancies
Am J Obstet Gynecol
(1987)

There are more references available in the full text version of this article.

Cited by (160)

The accuracy of sonographic fetal weight in very preterm infants (≤32 weeks)
2024, Journal of Gynecology Obstetrics and Human Reproduction
To examine the accuracy of sonographic fetal weight to predict birthweight in very preterm infants (<32 weeks), and to compare the accuracy of estimated fetal weight (EFW) between those small for gestational age (SGA) and those appropriate for gestational age (AGA).
A retrospective study was conducted of data recorded between January 2010 and March 2023. Included were women with singleton livebirths at 23+0–31+6 weeks who had an EFW within one week from delivery. Mean percentage error, mean absolute percentage error, and underestimation and overestimation rates were calculated. We compared the accuracy of EFW between SGA and AGA infants.
In total, 360 women were included. The mean absolute percentage error was 7.8 % (range 0 %–68.9 %); for 207 (57.5 %) infants the percentage error was within ±10 %. Overestimation error >10 % was observed in 102 (28.3 %) infants and errors >20 % in 34 (9.4 %). Among infants born in the periviable period (23+0 – 25+6 weeks; N = 56), the mean absolute percentage error was 9.8 % (range: 0 %–40.3 %); the value was within ±10 % for only 28 periviable infants (50 %) and exceeded 20 % for 16.1 %. Among SGA compared to AGA infants, the mean absolute percentage error was higher (11.1% vs. 6.6 %, p = 0.035). Overestimation error >10 % was more frequent among SGA than AGA infants (55 (49.1 %) vs. 47 (19.0 %), p < 0.001). In a multivariate logistic regression analysis, SGA status was independently associated with a higher mean percentage error (beta = 0.260, p < 0.001) and an increased risk of an error >10 % (odds ratio = 2.1, 95 % confidence interval 1.2–3.5, p = 0.008).
Sonographic EFW is limited in assessing very preterm infants, particularly those who are SGA or born during the periviable period. These limitations should be considered regarding impending very preterm births and concerns about abnormal fetal growth.
Cooking with liquefied petroleum gas or biomass and fetal growth outcomes: a multi-country randomised controlled trial
2024, The Lancet Global Health
Household air pollution might lead to fetal growth restriction during pregnancy. We aimed to investigate whether a liquefied petroleum gas (LPG) intervention to reduce personal exposures to household air pollution during pregnancy would alter fetal growth.
The Household Air Pollution Intervention Network (HAPIN) trial was an open-label randomised controlled trial conducted in ten resource-limited settings across Guatemala, India, Peru, and Rwanda. Pregnant women aged 18–34 years (9–19 weeks of gestation) were randomly assigned in a 1:1 ratio to receive an LPG stove, continuous fuel delivery, and behavioural messaging or to continue usual cooking with biomass for 18 months. We conducted ultrasound assessments at baseline, 24–28 weeks of gestation (the first pregnancy visit), and 32–36 weeks of gestation (the second pregnancy visit), to measure fetal size; we monitored 24 h personal exposures to household air pollutants during these visits; and we weighed children at birth. We conducted intention-to-treat analyses to estimate differences in fetal size between the intervention and control group, and exposure–response analyses to identify associations between household air pollutants and fetal size. This trial is registered with ClinicalTrials.gov (NCT02944682).
Between May 7, 2018, and Feb 29, 2020, we randomly assigned 3200 pregnant women (1593 to the intervention group and 1607 to the control group). The mean gestational age was 14·5 (SD 3·0) weeks and mean maternal age was 25·6 (4·5) years. We obtained ultrasound assessments in 3147 (98·3%) women at baseline, 3052 (95·4%) women at the first pregnancy visit, and 2962 (92·6%) at the second pregnancy visit, through to Aug 25, 2020. Intervention adherence was high (the median proportion of days with biomass stove use was 0·0%, IQR 0·0–1·6) and pregnant women in the intervention group had lower mean exposures to particulate matter with a diameter less than 2·5 μm (PM_2·5; 35·0 [SD 37·2] μg/m³ vs 103·3 [97·9] μg/m³) than did women in the control group. We did not find differences in averaged post-randomisation Z scores for head circumference (0·30 vs 0·39; p=0·04), abdominal circumference (0·38 vs 0·39; p=0·99), femur length (0·44 vs 0·45; p=0·73), and estimated fetal weight or birthweight (–0·13 vs –0·12; p=0·70) between the intervention and control groups. Personal exposures to household air pollutants were not associated with fetal size.
Although an LPG cooking intervention successfully reduced personal exposure to air pollution during pregnancy, it did not affect fetal size. Our findings do not support the use of unvented liquefied petroleum gas stoves as a strategy to increase fetal growth in settings were biomass fuels are used predominantly for cooking.
US National Institutes of Health and Bill & Melinda Gates Foundation.
For the Kinyarwanda, Spanish and Tamil translations of the abstract see Supplementary Materials section.
BabyNet＋＋: Fetal birth weight prediction using biometry multimodal data acquired less than 24 hours before delivery
2023, Computers in Biology and Medicine
Accurate prediction of fetal weight at birth is essential for effective perinatal care, particularly in the context of antenatal management, which involves determining the timing and mode of delivery. The current standard of care involves performing a prenatal ultrasound 24 hours prior to delivery. However, this task presents challenges as it requires acquiring high-quality images, which becomes difficult during advanced pregnancy due to the lack of amniotic fluid. In this paper, we present a novel method that automatically predicts fetal birth weight by using fetal ultrasound video scans and clinical data. Our proposed method is based on a Transformer-based approach that combines a Residual Transformer Module with a Dynamic Affine Feature Map Transform. This method leverages tabular clinical data to evaluate $2 D + t$ spatio-temporal features in fetal ultrasound video scans. Development and evaluation were carried out on a clinical set comprising 582 2D fetal ultrasound videos and clinical records of pregnancies from 194 patients performed less than 24 hours before delivery. Our results show that our method outperforms several state-of-the-art automatic methods and estimates fetal birth weight with an accuracy comparable to human experts. Hence, automatic measurements obtained by our method can reduce the risk of errors inherent in manual measurements. Observer studies suggest that our approach may be used as an aid for less experienced clinicians to predict fetal birth weight before delivery, optimizing perinatal care regardless of the available expertise.
Accuracy of estimated fetal weight in extremely preterm infants and the impact of prepregnancy body mass index
2022, American Journal of Obstetrics and Gynecology MFM
Citation Excerpt :
Several formulas have been developed to estimate fetal weight from ultrasound measurements of various fetal dimensions (biparietal diameter, head circumference [HC], abdominal circumference [AC], and femur length [FL]).4,5 The validity of these formulas has been demonstrated in clinical practice with an estimated systematic error of ≤10%.5–7 Furthermore, the error rate of ultrasound ranges from 2% to 20%, with rare outliers >20% between ultrasound estimations and BW.
Antenatally, we rely on ultrasound estimated fetal weight as a proxy for birthweight to inform discussions regarding perinatal morbidity and mortality. Maternal obesity may negatively impact the quality of ultrasound imaging, and thus, understanding the associations between obesity and estimated fetal weight in the preterm period is important.
Given the rising obesity rates and association with preterm birth, we sought to determine the accuracy of ultrasound-derived estimated fetal weight in predicting birthweight in preterm infants by prepregnancy body mass index and to evaluate the accuracy of estimated fetal weight in predicting birthweight between small-for-gestational-age and appropriate-for-gestational-age infants.
We included all women who delivered a live-born singleton infant between 23 0/7 and 31 6/7 weeks of gestation and had an ultrasound estimated fetal weight within 7 days before delivery. We calculated the mean percentage difference between estimated fetal weight and birthweight and the absolute percent difference. Excess error was defined as an absolute percentage difference of >20%. We used multivariable modified Poisson models to determine the association between prepregnancy body mass index and small for gestational age and excess ultrasound error.
Our cohort included 641 infants with a mean gestational age of 28.0±2.6 weeks and a mean birthweight of 1110±425 g. More than one-third of our cohort were obese (227 [35%]). The mean percentage difference between estimated fetal weight and birthweight was 7.7%±11.2% among all infants. Ultrasound overestimated birthweight in 77% of the cohort (n=492). Stratified by body mass index, the mean percentage differences between estimated fetal weight and birthweight were 6.7%±11.0% in women with normal weight and 9.5%±12.0% in women with obesity (P=.02). The mean percentage differences between estimated fetal weight and birthweight were 11.0%±11.0% in small-for-gestational-age infants (n=80) and 7.1%±11.0% in appropriate-for-gestational-age infants (P<.001). Small-for-gestational-age infant was associated with an increased risk of excess ultrasound error with an adjusted relative risk of 2.3 (95% confidence interval, 1.2–4.3).
Although ultrasound estimated fetal weight overestimated birthweight, particularly in small-for-gestational-age infants, most estimates were within 10% of actual birthweight. Obesity and small-for-gestational-age birth were both associated with an increased risk of excess ultrasound error (≥20%) in estimating birthweight.
Prediction of fetal macrosomia using two-dimensional and three-dimensional ultrasound
2019, European Journal of Obstetrics and Gynecology and Reproductive Biology
Citation Excerpt :
Fetal macrosomia can be defined as birthweight above 4000 g regardless of the gestational age or as birthweight above the 95th/97th percentile for the given gestation [1–4] and is an acknowledged risk factor for intrapartum dystocia and other maternal and perinatal complications [5,6]. The evaluation of the estimated fetal weight (EFW) at term is currently not routinely indicated given its limited accuracy [7–10]. Additionally, national and international societies have so far omitted to recommend how to manage the pregnancies where a macrosomic/LGA fetus is suspected.
The estimation of the fetal weight by three-dimensional (3D) ultrasound (US) with fractional thigh volume (TVol) has been suggested to be more accurate than two-dimensional (2D) US particularly within the context of fetuses at risk of macrosomia. The objective of this study was to compare the accuracy of 2D US and 3D US with two different methods of projection for the identification of fetal macrosomia at term.
Prospective study which included women at risk for fetal macrosomia referred for fetal biometry between 34⁺⁰-36⁺⁶ weeks. The estimated fetal weight (EFW) was computed using 2D US and the Hadlock Model IV or through 3D US and the Model VI by Lee et al. The projection of the EFW at the time of delivery was performed by using Yudkin’s chart percentiles and the gestation-adjusted projection (GAP) method.
Overall, 230 patients were included. Paired comparison between 2D-US-EFW and 3D-US-EFW with either method of projection of the EFW at birth suggested different properties of the techniques, being 2D-US-EFW associated with higher sensitivity and 3D-US-EFW with higher specificity, PPV and LR + . At ROC curve no difference was found in the prediction of birthweight ≥90th centile using 2D-US-EFW or 3D-US-EFW (AUC 0.831, 95%CI 0.768-0.894 versus AUC 0.860, 95%CI 0.799-0.920, respectively, p 0.37) nor in the prediction of birthweight >95th centile with 2D-US-EFW compared to 3D-US-EFW (0.803, 95%CI 0.731-0.874 versus 0.866, 95%CI 0.805-0.926, respectively, p 0.07). Similarly, a non-significant difference in the accuracy of the prediction of birthweight >4000 g (AUC 0.788, 95%CI 0.716-0.859 for 2D-US-EFW vs AUC 0.802, 95%CI 0.723-0.880 for 3D-US-EFW, p 0.72) and >4500 g (0.828, 95%CI 0.720-0.936 for 2D-US-EFW vs 0.858, 95%CI 0.759-0.956 for 3D-US-EFW, p 0.71) with the GAP method could be demonstrated.
Within a population at risk of fetal macrosomia the performance of 3D-US-EFW is similar to that of 2D-US-EFW in the prediction of macrosomia at term regardless of the method used for the projection of the EFW, however different properties were noted between the two techniques. Such finding suggests a potential complementary role of the techniques which warrants evaluation in future research.
A modified model can improve the accuracy of foetal weight estimation by magnetic resonance imaging
2019, European Journal of Radiology
To determine whether birth weight can be reliably estimated using three-dimensional (3D) magnetic resonance imaging (MRI) foetal body volume at term.
Foetuses between 37⁺⁵ weeks and 41 weeks of gestation were delivered within 7 days after MRI and ultrasound (US) examinations. 3D foetal models were reconstructed from MRI data, and body volume was calculated. The MRI-based weight estimations were calculated using the Baker equation and the modified Baker equation with a higher density coefficient. The US-based weight estimations were determined using the formula by Hadlock. Estimations based on MRI and US were compared with the birth weights.
Among 22 foetuses that underwent both US and MRI evaluations within 48 h before labour, the mean random errors for the estimated weight based on US, the Baker equation and the modified Baker equation were 6.5%, 4.8%, and 4.8%, respectively, and these methods correctly estimated the weights of 77.3%, 86.4% and 100% of the foetuses to within 10% of the actual birth weight. The weights of 95.5% of the foetuses were underestimated by the Baker equation. Similar findings were observed among 103 estimations based on both US and MRI within 7 days before delivery. The mean relative error of the MRI-determined estimate of foetal weight using the modified Baker equation was not significantly associated with foetal sex, birth weight, gestational age at MRI examination, the MRI-to-delivery interval or the type of MRI scanner.
A modified Baker equation with a high-density coefficient can improve the accuracy of foetal weight estimation based on 3D MRI foetal volume at term, and its accuracy was not significantly affected by foetal characteristics or the type of MRI scanner among births occurring within 7 days after examinations.

View all citing articles on Scopus

View full text

Sonographically estimated fetal weights: Accuracy and limitation

Abstract

Am J Obstet Gynecol

Am J Obstet Gynecol

Am J Obstet Gynecol

Am J Obstet Gynecol

Am J Obstet Gynecol

Am J Obstet Gynecol