Accuracy Of Estimated Fetal Weight Research Articles

Pre-delivery BMI and the Accuracy of Fetal Weight Estimation in Very Preterm Infants

ObjectivesTo examine the relation between maternal pre-delivery BMI and the accuracy of sonographic estimated fetal weight (EFW) in very preterm infants (<32 weeks gestation). MethodsThis retrospective study included singleton infants born between January 2010 and March 2023, at gestational ages 230 to 316 weeks, at a tertiary university-affiliated hospital. Absolute weight, percentage error, absolute percentage error, and overestimation and underestimation of EFW were compared between women with pre-delivery normal weight (BMI 18.5–24.99 kg/m2), overweight (BMI 25.0–29.99 kg/m2), and obesity (BMI >35.0 kg/m2). Multivariate linear regression analyses adjusted for potential confounders were performed to assess relations of maternal pre-conception and of pre-delivery BMI, with EFW accuracy. ResultsIncluded were 286 pregnancies. The absolute difference, percentage error, absolute percentage error, error within the 10% range, and underestimation or overestimation of EFW were similar between the groups. The multivariate linear regression analyses did not show significant associations of pre-conceptional BMI or of pre-delivery BMI with the percentage error. However, for small for gestational age compared to appropriate for gestational age fetuses, the percentage error was greater (8.9% vs. –0.6%, β = 0.35, P < 0.001) and the absolute percentage error was greater (11.0% vs. 6.7%, P < 0.001). Small for gestational age fetuses were at risk of fetal weight overestimation (percentage error exceeding 15%); OR 7.20 (95% CI 2.91–17.80). ConclusionsMaternal pre-delivery BMI was not found to be related to EFW accuracy in very preterm infants. Nevertheless, EFW should be interpreted carefully, as it may underdiagnose poor fetal growth in this population.

Comparison of a Two (32/38 Weeks) versus One (36 Weeks) Ultrasound Protocol for the Detection of Decreased Fetal Growth and Adverse Perinatal Outcome.

Third-trimester ultrasound has low sensitivity to small for gestational age (SGA) and adverse perinatal outcomes (APOs). The objective of this study was to compare, in terms of cost-effectiveness, two routine third-trimester surveillance protocols for the detection of SGA and evaluate the added value of a Doppler study for the prediction of APO. This was a retrospective observational study of low-risk pregnancies that were followed by a two growth scans protocol (P2) at 32 and 38 weeks or by a single growth scan at 36 weeks (P1). Ultrasound scans included an estimated fetal weight (EFW) in all cases and a Doppler evaluation in most cases. A total of 1011 pregnancies were collected, 528 with the P2 protocol and 483 with the P1 protocol. While the two models presented no differences for the detection of SGA in terms of sensitivity (47.89% vs. 50% p = 0.85) or specificity (94.97 vs. 95.86% p = 0.63), routine performance of two growth scans (P2) led to a 35% cost increase. The accuracy of EFW for the detection of SGA showed a noteworthy improvement when reducing the interval to labor, and the only parameter with predictive capacity of APO was the cerebroplacental ratio at 38 weeks. In low-risk pregnancies, the higher costs of a two-scan growth surveillance protocol at the third trimester are not justified by an increase in diagnostic effectivity.

The accuracy of sonographic fetal weight in very preterm infants (≤32 weeks)

ObjectiveTo 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). Study designA 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. ResultsIn 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). ConclusionsSonographic 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.

Investigating the accuracy of Johnson’s rule in estimating fetal weight

BACKGROUND: Birth weight has a significant impact on perinatal mortality. Therefore, the estimation of fetal weight greatly influences the policies necessary for care during and after delivery. We aimed to investigate Johnson’s rule in estimating fetal weight. MATERIALS AND METHOD: This study was a single-group longitudinal study that was conducted in 6 months from October 2021 to April 2022 on 150 pregnant women in Isfahan-Iran. The sampling method was accessible. Inclusion criteria include being term, singleton, without abnormality, intact membranes, cephalic presentation, and exclusion criteria include diagnosed polyhydramnios or oligohydramnios and mother’s abdominal or pelvic known masses. After completing the informed consent, fetal weight was estimated by Johnson’s rule and was compared with the birth weight. Descriptive and analytical statistics (mean-standard deviation (SD), number-percentage, t-paired, and Spearman’s correlation coefficient) were used to achieve the objectives of the study. The receiver operating characteristic (ROC) curve was also used to determine the sensitivity, specificity, and positive and negative predictive value of Johnson’s law. RESULT: The mean (SD) birth weight was 3032.88 ± 481.11 g and the mean (SD) estimated fetal weight (EFW) by the clinical method was 3152.15 ± 391.95 g. There was a significant difference between the averages (P &lt; 0.001). The percentage error of EFW showed a significant negative correlation (r = -0.286; P &lt; 0.05) with gestational age (GA) and a significant positive correlation (r = 0.263; P &lt; 0.05) with the fetal head station. The sensitivity and specificity of EFW with Johnson’s rule, in normal fetal birth weight, were higher than in low birth weight fetal. The accuracy of EFW with ± 10% of the actual weight was higher in average for gestational age (AGA) (84.3%) and high-for-gestational-age (LGA) (70%) than in low-for-gestational-age (SGA) (4%). The EFW mean percentage error in SGA was higher than in the other two weight groups. This method, especially for AGA and LGA fetuses, can be a suitable alternative to other weight estimation methods. CONCLUSION: Clinical estimation of weight via Johnson’s rule due to availability and no cost can be a suitable method for managing childbirth based on fetal weight.

Accuracy of sonographic fetal weight estimation and prediction of birth-weight discordance in twin pregnancy: large single-center study.

To determine the accuracy of sonographic fetal weight estimation in predicting birth weight (BW) and BW discordance in twin gestations, and to evaluate maternal and fetal characteristics that may affect the accuracy of this assessment. This was a retrospective cohort study of all twins delivered at a single tertiary medical center between 2010 and 2021. Twin gestations for which sonographic estimation of fetal weight was performed within the week preceding delivery were included. Statistical analysis was performed to evaluate the strength of the correlation between sonographic estimated fetal weight (EFW) and BW, and to determine the impact of maternal and fetal factors on the accuracy of sonographic estimation. The study included 2154 twin pregnancies. There was a strong correlation between sonographic EFW and corresponding BW for all twins (r = 0.922; P < 0.001). Strong correlations were observed for both the presenting and non-presenting cotwin (r = 0.921 and r = 0.922, respectively; both P < 0.001), as well as the larger and smaller cotwin (r = 0.928 and r = 0.934, respectively; both P < 0.001). The overall mean ± SD absolute error of sonographic EFW was 7.41 ± 6.81%. This error was greater for the non-presenting cotwin compared with the presenting cotwin (7.99 ± 6.12% vs 7.17 ± 5.64%; P < 0.001), and for the smaller cotwin compared with the larger cotwin (8.56 ± 7.50% vs 6.58 ± 5.47%; P < 0.001). Advanced gestational age at scanning was correlated inversely with the mean absolute error of sonographic EFW. Multivariate logistic regression indicated that an earlier gestational age at scanning, being the non-presenting cotwin and being the smaller cotwin were independent risk factors for sonographic EFW inaccuracy. Pregnancies in which the presenting twin was estimated to be the smaller cotwin had twice the rate of false-positive BW discordance compared with pregnancies in which the presenting twin was estimated to be the larger cotwin (36.0% vs 13.0% for BW discordance > 15%, 35.0% vs 17.0% for BW discordance > 20% and 37.7% vs 12.1% for BW discordance > 25%; all P < 0.001). The error in sonographic EFW discordance was not related to chorionicity, the position of the presenting fetus or gestational age at the time of fetal weight estimation. Sonographic estimation of fetal weight within 7 days before delivery accurately predicts BW in twin pregnancy. Sonographic EFW accuracy is reduced for the non-presenting twin, the smaller cotwin and when delivery occurs at an earlier gestational age. Sonographic estimation of fetal weight discordance is less accurate when the presenting twin is the smaller cotwin. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Is accuracy of estimated fetal weight improved by better image quality scores?

To assess in a group of ultrasound operators of various levels of experience the predictive value of systematic quality scoring to assess estimated fetal weight (EFW) validity. Screenshots, sonographer experience, and neonate birth weight were collected for 131 ultrasound examinations in the 7 days before birth. The difference (EFW error) between projected birth weight (EFW + [30 g × interval in days to birth]) and actual birth weight was then assessed (absolute value). Three senior sonographers rated all the screenshots (International Society of Ultrasound in Obstetrics and Gynecology 16-point score for image quality) and interobserver reproducibility was assessed concomitantly. The impact of the score on EFW accuracy was then assessed (univariate analysis). Receiver operating characteristic curves allowed us to assess the score's positive predictive value (PPV) for accurate EFW. Mean birth weight was 2998 ± 954 g and mean EFW error was 8.6% ± 7.1%. Both the sonographer's experience and score significantly impacted the EFW error (P< 0.05). The PPVs of systematic image scores for identifying an EFW error greater than 10% and greater than 15% were appropriate for clinical use (areas under the curve 0.61 and 0.70, respectively). Score reproducibility was modest. Low image scores and limited ultrasound expertise are associated with an increased risk of inaccurate EFW.

Ultrasound estimation of fetal weight accuracy in a regional hospital: A retrospective audit

AbstractIntroductionUltrasound estimated fetal weight (EFW) is a vital part of prenatal care. We aimed to determine the accuracy of sonographic EFW at a regional Australian hospital, explore factors associated with EFW accuracy and review accuracy calculation methods.MethodsUltrasound EFW (Hadlock C) was calculated within one week of a live delivery, for 357 singleton pregnancies. EFW accuracy, the difference between EFW, and live birthweight (LBW), were quantified using percentage error (PE); absolute error (AE); ‘signed’ error and AE ≤10% of LBW.ResultsEstimations of accuracy varied by calculation method, with PE smaller (mean 2.3% [CI 1.5, 3.1], median PE 2.4% [IQR −3.4, 6.7]) than AE (mean 6.4% [CI 5.9, 6.9], median AE 5.1% [IQR 2.7, 9.0]). Signed error indicated the majority of EFWs were overestimates and 80.1% of EFW calculations had an AE within 10% of LBW. EFW inaccuracy (AE ≥10% of LBW) varied between sonographers (p = .023) and scan to delivery interval (p = .003).ConclusionsEFW accuracy rates at the regional hospital were similar to published error rates. EFW accuracy varied with sonographer and with time from scan to delivery. Absolute error provides more useful and comparable information than percentage error of EFW.

Analysis of factors influencing ultrasound-based fetal weight estimation.

Determining the mean deviation between estimated fetal weight (EFW) measured by ultrasound biometry and the real final birth weight and defining the factors influencing the accuracy of weight estimation. Estimated weight of the fetus before birth is valuable information for obstetricians particularlyin choosing the method, management, and timing of delivery. The retrospective study analyzed 331 medical records of induced labor between January and June 2021. Fetal weight estimation was calculated using Hadlock formulas. The anamnestic data were obtained from medical records, namely: maternal age, maternal BMI, parity, date of the last ultrasonography (USG) before delivery, fetal presentation, placental location, EFW (including the physician's name performing the measurement, and time of the measurement), gestational age of the fetus, date of birth, fetal gender, neonatal weight and length. The correlations between the weight deviation and other factors were expressed using the Pearson and Phik (Φk) correlation coefficients. The Bland Altman method was used to visualize the correspondence between the two variables. The hypotheses were based on the acquired knowledge and then tested by Mann-Whitney U, Kruskal-Wallis, and ANOVA statistical tests, as required by the hypotheses and input data. The mean EFW in the studied group was 3,459 ± 435 g, and the mean actual birth weight was 3,508 ± 508 g. The mean absolute deviation between monitored weight parameters was 260.27 g. The mean real birth weight was higher compared to EFW by 4.873g. A significant effect on EFW was observed for the following factors: time interval between sonographic weight estimation and delivery (less than 7 days), high maternal BMI (> 30 kg/m2), maternal age, and neonatal weight and length. The factors of fetal presentation, placental location, amniotic fluid volume, fetal gender, gestational age, parity, or those of examiner did not seem to impact EFW accuracy in our study. The time interval between sonographic weight estimation and delivery (shorter than 7 days), maternal BMI over 30 kg/m2, maternal age, neonatal weight and length are all factors significantly associated with the accuracy of ultrasound-based fetal weight estimation (Tab. 2, Ref. 13). Text in PDF www.elis.sk Keywords: ultrasound, biometry, fetal weight estimation.

Discriminatory capacity of prenatal ultrasound measures for large-for-gestational-age birth: A Bayesian approach to ROC analysis using placement values.

Predicting large fetuses at birth is of great interest to obstetricians. Using an NICHD Scandinavian Study that collected longitudinal ultrasound examination data during pregnancy, we estimate diagnostic accuracy parameters of estimated fetal weight (EFW) at various times during pregnancy in predicting large-for-gestational-age. We adopt a placement value based Bayesian regression model with random effects to estimate ROC curves. The use of placement values allows us to model covariate effects directly on the ROC curves and the adoption of a Bayesian approach accommodates the a priori constraint that an ROC curve of EFW near delivery should dominate another further away. The proposed methodology is shown to perform better than some alternative approaches in simulations and its application to the Scandinavian Study data suggests that diagnostic accuracy of EFW can improve about 65% from week 17 to 37 of gestation.

285 Accuracy of estimated fetal weight in extremely preterm infants and the impact of obesity

Obesity is increasingly common among reproductive age women, placing them at increased risk for obstetrical complications including preterm birth. Our objective was to determine the accuracy of ultrasound derived estimated fetal weight (EFW) in preterm infants born less than 32 weeks and determine if accuracy varied by prepregnancy body mass index (BMI). We also sought to evaluate the accuracy of EFW among small for gestational age (SGA) versus appropriately grown (AGA) preterm infants. We included women who delivered between 230/7 and 316/7 weeks’ gestation who had an ultrasound EFW within 7 days of delivery. We excluded women with missing prepregnancy BMI data (n=13). Mean percentage difference and median absolute percentage difference between EFW and BW were calculated using the formula (EFW-BW)/BWx100%. We then used Anova or t-test to compare the accuracy of EFW between groups. A total of 641 women were included in our cohort with a mean gestational age of 28.3 ± 2.6 weeks and mean birthweight of 1110.3 ± 425.3g. Among women in the cohort, a total of 3.6% were underweight, 37.3% were of normal weight, 23.7% were overweight, and 35.4% were obese. The mean percentage difference between EFW and BW was 7.7 ± 11.2% among all infants. As can be seen in Fig 1, EFW is skewed toward overestimating BW. The median absolute percentage difference between EFW and BW was 9.2% (IQR: 4.3-15.2). The mean accuracy of EFW varied by BMI category (Fig 2) with a mean accuracy of 6.7 ± 11.3% in normal weight women and 9.5 ± 11.5 % in obese women (p=0.02). Among SGA infants (n=125), the mean percentage difference between EFW and BW was 12.6 ± 10.4%, versus 6.5 ± 11.0% among AGA infants (p<0.001). While ultrasound EFW overestimates birthweight in this cohort, most estimates were within 10% of actual birthweight. The accuracy of EFW was worse in obese women compared to normal weight women. Ultrasound EFW also significantly overestimated BW in SGA infants. This is important when counseling women facing preterm delivery, especially those who are predicted to be small for gestational age.View Large Image Figure ViewerDownload Hi-res image Download (PPT)

The effect of fetal weight on the accuracy of sonographic weight estimation among women with diabetes

Objective The assessment of sonographic estimated fetal weight (EFW) enables identification of fetuses in the extremes of weight, thus aiding in the planning and management of peripartum care. There are conflicting reports regarding the accuracy of EFW in diabetic mothers. We aimed to study the factors associated with the accuracy of EFW at term, specifically the role of gestational and pre-gestational diabetes in this setting. Methods A retrospective study including all women carrying singleton term gestations who delivered within a week following a sonographic fetal weight estimation between 2011 and 2019. Accurate EFW was defined as within 10% of the actual birthweight. We allocated the study cohort into two groups: (1) Accurate EFW (2) inaccurate EFW. Both groups were compared in order to identify factors associated with the inaccuracy of EFW. Results Overall, 41,263 deliveries were available for evaluation, including 412 (1.0%) deliveries among women with pre-gestational diabetes and 4,735 (11.5%) among women with gestational diabetes. Of them, 7,280 (17.6%) had inaccurate EFW. Inaccurate EFW was associated with nulliparity, OR 0.82 [95% CI] (0.78–0.87), oligohydramnios, OR 0.81 [95% CI] (0.71–0.93), pregestational diabetes, OR [95% CI] 0.61 (0.50–0.79), and extremity of fetal weight; <2,500 grams–OR [95% CI] 0.37 (0.33–0.41) and >4,000 grams OR [95% CI] 0.52 (0.48–0.57). On multiple regression analysis, the following factors were independently associated with inaccurate EFW: pregestational diabetes, OR [95% CI] 0.58 (0.46–0.73), p < .001, nulliparity, OR [95% CI] 0.86 (0.82–0.91), p < .001 and higher fetal weight (for each 500 grams), OR [95% CI [1.25 (1.21–1.30), p < .001. On analysis of different weight categories, pregestational diabetes was associated with inaccurate EFW only in those with birthweight >3,500 grams, OR [95% CI] 0.37 (0.24–0.56) (p < .001). Conclusion Among pregestational diabetic women, the accuracy of sonographic EFW when assessed to be >3,500 grams is questionable. This should be taken into consideration when consulting women and planning delivery management. Synopsis Among pregestational diabetic women, the accuracy of estimated sonographic fetal weight higher than 3,500 grams is of limited accuracy.

Estimated fetal weight accuracy in pregnancies with preterm prelabor rupture of membranes by the Hadlock method

Objective We aimed to assess the accuracy of the estimated fetal weight (EFW) to predict the birthweigth (BW) in pregnancies complicated by PPROM. Study design This study was a secondary analysis of a prospective cohort of pregnancies with PPROM. We included singleton pregnancies from 23 to 36 + 6 weeks, mothers from 13 to 46 years of age, and those with an EFW within two weeks of delivery. We excluded pregnancies with complex fetal anomalies and fetal demise. The accuracy of the EFW was determined by the absolute percent difference between BW and EFW ([BW-EFW]/BW*100%). T tests and linear regression were performed for statistical analysis. Results The mean percent difference of BW vs. EFW was 8.72 ± 6.94%. The EFW was more accurate (8.24 ± 6.81 vs. 13.31 ± 6.88%, p = .027) and had more measurements with a absolute difference < 10% (70% vs. 30%; p = .034) when performed within seven days of delivery. The EFW accuracy decreased with anhydramnios (11.37 ± 7.06 vs. 7.69 ± 6.77%, p = .020), but the measurements with an absolute difference <10% was not significantly different (p = .27) with anhydramnios. Conclusion In PPROM, the EFW within seven days to delivery by Hadlock accurately predicts the birthweight with a mean absolute difference of 8.2%. Brief rationale There are a limited number of studies evaluating the accuracy of the EFW in pregnancies with PPROM in the last four decades.

1046: Accuracy of estimated fetal weight assessment in fetuses with congenital diaphragmatic hernia

Estimated fetal weight (EFW) is determined by a formula that includes measurement of the fetal abdominal circumference. There is an accepted range of error of up to 20% in either direction for accuracy of EFW. The degree of error is potentially higher in fetuses with congenital diaphragmatic hernia (CDH), in which the abdominal contents are displaced into the fetal thorax, which may affect measurement of the abdominal circumference. There is no universally accepted method for assessing EFW in fetuses with CDH, and there are mixed results in the literature reporting on accuracy of EFW in these cases. This study aims to assess the accuracy of standard EFW assessment in fetuses with CDH. We hypothesize that standard EFW assessment will underestimate the EFW of fetuses with CDH due to decreased fetal abdominal circumference measurement. This is a retrospective cohort of fetuses diagnosed with CDH at a single center from 2012 to 2018. We excluded fetuses with multiple anomalies or confirmed chromosome abnormalities. EFW was calculated using the Hadlock formula with standard measurements of the fetal head, abdominal circumference, and femur length. To account for time interval between final growth ultrasound and birth, we used published estimates of fetal growth rate to establish a “projected” EFW. The percent difference between the projected EFW and actual birthweight was compared using the Wilcoxon Signed-Rank test. Complete data were available for 77 fetuses with CDH. The majority of fetuses (n=59, 76.6%) had left-sided CDH. The median [IQR] projected EFW was similar to the median birthweight at 3177g [2691-3568] and 3180g [2630- 3500], respectively. The median percent difference between projected birthweight and actual birthweight was 6.34% [3.21-11.83]. We found that the EFW was underestimated in a minority of cases (n=43, 44.2%). The median maternal BMI in our population was 31.4kg/m2 [25.2-37.1]. The median gestational age at delivery was 38w4d [37w1d-39w1d], with a median 13 [7-20] days between final EFW and delivery. In fetuses with CDH, standard measurements for fetal EFW show accuracy that is at least comparable to previously established margins of error for ultrasound assessment of fetal weight. Standard EFW assessment remains an appropriate method of estimating fetal weight in fetuses with CDH.

Prospective assessment of INTERGROWTH-21st and World Health Organization estimated fetal weight reference curves.

To assess the suitability of the new INTERGROWTH-21st and World Health Organization (WHO) estimated fetal weight (EFW) references in a Southern Chinese population. A secondary aim was to determine the accuracy of EFW by assessing the difference between EFW and actual birth weight. This was a prospective cross-sectional cohort study. Viable singleton pregnancies at 11-13 weeks' gestation were recruited to undergo a single standardized fetal biometric scan after 20 weeks. The gestational age at which the scan was performed was allocated randomly at the time of recruitment. EFW was predicted using both the Hadlock and INTERGROWTH-21st weight estimation model formulae. Population-specific EFW references were constructed. Z-scores were used to compare these references against the INTERGROWTH-21st and WHO international size references. Gestational-age-adjusted projection was used to assess the difference between EFW on the day of delivery and birth weight for fetuses having biometry scans ≥ 34 weeks. Fetuses of 970 participants had biometry scans. The median number of scans per gestational week was 48 (interquartile range, 43-53). Z-score comparison indicated that the WHO 10th , 50th and 90th centiles of the EFW reference were consistently higher than the corresponding local centiles, whilst the INTERGROWTH-21st 10th centile was lower. Fewer than 2% of fetuses scanned at or after 34 weeks would be considered as potentially large-for-gestational age, irrespective of which model was used to predict weight. Adopting the WHO international reference would result in approximately one in six fetuses being regarded as potentially small-for-gestational age, 50% more than the number determined using a population-specific reference. Systematic errors of extrapolated EFW were similar, ranging from 5.5% to 7.4%. Centers seeking to use new references, such as the INTERGROWTH-21st and/or WHO international references, as a means of determining whether a fetus is small- or large-for-gestational age, would be advised to assess the suitability of these references within their own population using standardized methodology. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Effect of Maternal Body Mass Index and Amniotic Fluid Index on the Accuracy of Sonographic Estimation of Fetal Weight in Late Gestation.

The objective of this study was to determine the effect, if any, of maternal body mass index (BMI) and amniotic fluid index (AFI) on the accuracy of sonographic estimated fetal weight (EFW) at 40 to 42 weeks' gestation. This was a retrospective cohort study of singleton gestations with ultrasound performed at 40 to 42 weeks from 2010 to 2013. In this study, patients with documented BMI and sonographic EFW and AFI, concurrently, within 7 days of delivery were included. Chronic medical conditions and fetal anomalies were excluded from this study. The primary variable of interest was the rate of substantial error in EFW, defined as absolute percentage error (APE) >10%. A total of 1,000 pregnancies were included. Overall, the APE was 6.0 ± 4.5% and the rate of substantial error was 17.4% (n = 174). There was no significant difference in APE or rate of substantial error between BMI groups. In the final multivariable logistic regression model, the rate of substantial error was increased in women with oligohydramnios (OR 1.79; 95% CI: 1.10-2.92). Furthermore, oligohydramnios was significantly more likely to overestimate EFW while polyhydramnios was more likely to underestimate EFW. Maternal BMI did not affect the accuracy of sonographic EFW. Sonographic EFW may be affected by extremes of AFI in the postdates period. Maternal BMI does not affect EFW accuracy at 40 to 42 weeks.

Accuracy of Ultrasound Estimated Fetal Weight in Small for Gestational Age and Appropriate for Gestational Age Grown Periviable Neonates.

Clinicians use estimated fetal weight (EFW) as a proxy for birth weight (BW) in the antenatal period. Our objective was to compare the accuracy of EFW obtained by ultrasound to BW among infants born during the periviable period and determine if accuracy of EFW varied among small for gestational age (SGA) versus appropriate for gestational age (AGA) grown neonates. We included women who delivered between 230/7 and 256/7 weeks' gestation and had an EFW within 7 days of delivery. Mean percentage difference and median absolute percentage difference between EFW and BW were calculated. Our cohort included 226 neonates with a mean gestational age of 241/7 ± 0.8 weeks and median BW of 653 g (interquartile range [IQR]: 580-750 g). The median absolute percentage difference between EFW and BW of fetal weight estimates was 9.2% (IQR: 3.6-17.2). EFW overestimated BW for 75% (n = 171) of the cohort. Among SGA infants, the mean percentage difference in EFW and BW was 16.2 ± 19.4% versus 6.9% ± 13.1% in AGA infants (p = 0.019). EFW overestimated BW in this cohort. In addition, ultrasound was less accurate among infants born SGA. These data are important to consider when counseling families facing periviable delivery.

The Effect of the Amniotic Fluid Index on the Accuracy of Ultrasonographic-Estimated Fetal Weight.

Fetal weight estimation is one of the most important aspects of antenatal care. The effects of amniotic fluid volume on the accuracy of estimated fetal weight (EFW) depend on the amount of fluid, in particular whether it is polyhydramnios or oligohydramnios. Previous studies have reported conflicting results of the effects of amniotic fluid volume on EFW accuracy. The aim of the study was to evaluate the effects of isolated oligohydramnios cases and polyhydramnios on the accuracy of EFW. A retrospective study was conducted at a tertiary center. The study groups consisted of 1069 term isolated oligohydramnios cases, 182 term isolated polyhydramnios cases, and 392 term-matched cases with a normal volume of amniotic fluid. Estimated fetal weight error was determined and expressed in terms of systematic error, calculated from mean percentage error and random error. The systematic error did not differ significantly between polyhydramnios and oligohydramnios cases (-3.60 [8.94%] vs -2.73 [9.7%]). The random error was 8.94% in polyhydramnios cases and 9.7% in oligohydramnios cases. The overestimation rate was 63.6% in polyhydramnios cases and 66.3% in oligohydramnios cases. There were no significant differences in the accuracy of EFW between oligohydramnios and polyhydramnios. However, there was a tendency for overestimation in both types of cases.

Impact of Fetal Weight Estimation on the Prediction of Neonatal Morbidity and Mortality at the Limit of Viability

Introduction: To determine the accuracy of estimated fetal weight (EFW) at the limit of viability in a delivery room setting and its impact on the prediction of neonatal outcome. Material and Methods: In this retrospective, single-center cohort study we included patients with preterm birth between 23⁰/₇ and 26⁰/₇ weeks of gestation. Neonates were divided into 3 groups according to birth weight at delivery (accuracy index 90-110%, <90%, >110%). Neonatal outcome for each group was categorized into survival with and without impairment and death, with a follow-up period of 6 weeks. Results: Eighty-seven newborns were included, with 62.1% accurately estimated. Gestational age at birth, fetal sex, maternal body mass index, and time interval between birth and ultrasound affected the accuracy of EFW. Chances of survival were significantly higher in the underestimated group for birth weight at delivery compared with estimated weight (p < 0.001), with risk of death being significantly lower (p < 0.001). The reverse was true for overestimated infants, for both risk of death and chances of survival. At 6 weeks' follow-up, there were significantly more deceased overestimated infants (p = 0.041). Discussion: Our study shows that inaccuracy of EFW at the limit of viability occurs frequently in a delivery room setting with a potential impact on neonatal outcome.

20 Termination of pregnancy for hypertensive disorders in the peri-viable period and accuracy of estimated fetal weight

Introduction The decision to terminate a pregnancy for hypertensive disorders in the periviable period is made based on the severity of the maternal condition on the one hand and the prospects for healthy neonatal survival on the other hand. These pregnancies are often complicated by severe intrauterine growth restriction. Ultrasound parameters are used to assess fetal condition and prognosis. Estimated fetal weight (EFW) is one of these parameters. Objective This study investigated the accuracy of EFW in women with severe preeclampsia where the decision was made to terminate the pregnancy without fetal surveillance and refraining from active neonatal support. Methods Eligible for this study are all women who underwent termination of pregnancy for preeclampsia in The Netherlands between January 2000 and January 2014. EFW is derived from ultrasound parameters using the Hadlock 3 formula. Actual birth weight is collected from the original medical files. Results 161 women fulfilled the inclusion criteria. 48 pregnancies were terminated 24 weeks’gestation. In these cases EFW had not an important role in counselling of the parents and decision making. 113 pregnancies were terminated beyond 24 weeks’gestation (mean 25 + 2 weeks, SD 9.4 days). The mean EFW in this group was 495 gram (SD 113 g). The mean birth weight was 508 g (SD 117). The mean difference EFW and actual birth weight was 13.3 g 95% CI −24.30 to −2.30, p = 0.018. In 25 cases the EFW was more than 10% underestimated (22%) and in 10 cases the EFW was more than 10% overestimated (9%). Conclusion The decision to refrain from interventions on fetal indication and active neonatal support is based on propects for healthy survival of the fetus. Birth weight was accurately predicted in 68% of the cases. This should be taken into account when counselling the parents in these rare cases.

Accuracy of Sonographic Fetal Weight Estimation in Bangladesh

Objective This study was conducted to determine the accuracy of estimated fetal weight (EFW) by ultrasound, compared with birth weight (BW), in Bangladesh. Methods This is a prospective, cross-sectional study on well-dated singleton fetuses. The accuracy of weight-prediction formula is determined by assessing how well the formula works in a group of fetuses scanned close to delivery. Results of previous studies were compared with those of this study. Results A total of 73 infants were included in the analysis to determine the accuracy of EFW. The mean absolute difference between ultrasound EFW and BW was −64.5 (±218.5) g, and the mean relative difference or the mean percentage error of fetal weight estimation was −1.4% (±7.6%). Conclusion Ultrasound is a reliable modality for estimating fetal weight in a Bangladeshi population using the head circumference, femur length, and abdominal circumference formula of Hadlock.