Ultrasonographic estimation of fetal weight: acquiring accuracy in residency

Accuracy of Estimated Fetal Weight by Ultrasound Versus Leopold Maneuver

ABSTRACT

Estimated fetal weight (EFW) is frequently used for clinical decision-making in obstetrics. The goals of this study were to determine the accuracy of EFW assessments by Leopold and ultrasound and to investigate any associations with maternal characteristics. Postgraduate years 1 and 2 obstetrics and gynecology resident physicians from Harbor-UCLA Medical Center from 2014 to 2020 performed EFW assessments on 10 preterm (<37 weeks' gestational age) fetuses by ultrasound biometry and 10 full-term (≥37 weeks' gestational age) fetuses by ultrasound biometry and Leopold maneuver. Assessments were included if the patients delivered within 2 weeks of the assessments. One thousand six hundred ninety-seven EFW assessments on 1183 patients performed by 33 residents were analyzed; 72.6% of sonographic full-term EFWs, 69% of Leopold full-term EFWs, and 61.5% of sonographic preterm EFWs were within 10% of the neonatal birth weight (BW). The lowest estimation error in our study occurred when actual BW was 3600 to 3700 g. After adjusting for BW, residents were found to have lower accuracy when the mother had a higher body mass index (BMI) for full-term estimation methods (Leopold and ultrasound, β = 0.13 and 0.12, P = 0.001 and 0.002, respectively). Maternal BMI was not related to estimation error for preterm fetuses ( β = 0.01, P = 0.75). Clinical and sonographic EFW assessments performed by obstetrics and gynecology junior residents are within 10% of neonatal BW much of the time. In our cohort, they tended to overestimate EFWs of lower-BW infants and underestimate EFWs of higher-BW infants. Accuracy of full-term EFW assessments seems to decrease with increasing maternal BMI.

Are Junior Residents Accurate at Predicting Fetal Weight? An Analysis of Junior Residents' Performance of Estimated Fetal Weight Using Ultrasound and Leopold's Maneuver

Background

Performing accurate estimated fetal weights (EFWs) is a critical skill developed in obstetrics residency training. Resident physicians are often the first to perform EFWs on obstetric patients when they enter care. Evaluating residents' accuracy in performing EFWs is crucial for assessing their achievement in residency training milestones and providing patient care.

Methods

As part of an educational initiative program between 2014 and 2020, postgraduate year 1 (PGY1) and postgraduate year 2 (PGY2) residents performed EFW measurements on 10 term (>37w0d) patients using ultrasound and Leopold's maneuver and 10 preterm (>24w0d and <37w0d) patients using ultrasound. Clinical characteristics, mode of delivery, and actual birthweights (BWs) were recorded for each patient. The accuracy of these estimates was evaluated using mixed-effect regression models.

Results

Thirty-three residents, 1127 deliveries, and 1790 EFW measurements were evaluated. Overall, the percentage of residents with estimations within 10% of actual BW went up in PGY2 for Leopold's and ultrasound term births, but not for preterm ultrasound births. Maternal body mass index and actual BW were associated with absolute percentage estimation error. After adjusting for these variables, there was a statistically significant decrease in error between PGY1 and PGY2 for Leopold's method in term births; ultrasound (term and preterm) showed more modest reductions in error during PGY2.

Discussion

Resident physicians have accurate estimates of EFWs early in their training, beginning in their first year of residency by both Leopold's maneuver and ultrasound. Furthermore, PGY2 residents performed better than PGY1 residents for Leopold's method.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSION

Low image scores and limited ultrasound expertise are associated with an increased risk of inaccurate EFW.

The birth weight of macrosomia influence the accuracy of ultrasound estimation of fetal weight at term

OBJECTIVE

To evaluate and analyze the accuracy of ultrasound estimation of the fetal weight of Macrosomia at term.

METHOD

The instruments used were α6(Aloka; Japan) color Doppler ultrasound imagers, and vinno 80 (feieno; China) with a frequency of 3.5 MHz. The formula used to calculate the estimated fetal birth weight (EFW) was that proposed by Hadlock et al. (Hadlock 2). The biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL) measurements were performed strictly following the practice guidelines. Detailed measurement standards are shown in the figure and the table in the text. Macrosomia is typically defined as a birth weight above the 90th percentile for gestational age or >4000 g.Two indexes were used to calculate the error between EFW and birth weight (BW): Simple error (SE = BW - EFW); Absolute percentage error (APE, which reflects this percentage in absolute value, percentage error [PE = SE/BW] × 100). In order to better evaluate the measurement results, we made the following definitions: 1. When APE > 15%, the measurement deviation is significant. 2. The ratio of those cases with APE > 15% to the total number of cases measured by a sonographer was greater than 20%, indicating that the sonographer was prone to significant measurement deviation.

RESULT

A total of 374 cases were analyzed. The mean maternal age was 31.48 (±15.93) years. Each pregnant woman carries only one fetus. The mean gestational age at delivery was 39.93 (±0.84) weeks. There were 245 male infants (65.5%), 129 female infants (34.5%), 214 cesarean section (57.2%), and 160 vaginal delivery (42.7%). 339 cases (90.64%) were estimated to be lower than the actual BW. The estimated weight was higher than the actual weight in 35 cases, accounting for 9.36%.The APE>15% in 56 cases, accounting for 14.97%. The accuracy of estimated fetal weight was closely related to the BW of the fetus and had no significant correlation with the seniority of the physician, the gender of the fetus, and the fetal position.

CONCLUSION

Studies on macrosomia have shown that the BW of macrosomia tends to be underestimated, which is also reflected in the results of this study. The accuracy of estimated fetal weight still needs to be improved. Our study found that the accuracy of estimated fetal weight was closely related to the BW of the fetus and had no significant correlation with the seniority of the physician, the gender of the fetus, and the fetal position. The correlation between the section and calculation formula on the measurement accuracy needs to be studied. Through systematic data analysis, we can find the doctors whose measurements are relatively inaccurate in our department and carry out targeted quality control to improve the measurement accuracy.

Quantitating skill acquisition with optical ultrasound simulation

Objective

To investigate and compare the effect of simulator training on quantitative scores for ultrasound-related skills for trainees with novice level ultrasound experience and expert ultrasound operators.

Methods

Three novice (comprising of 11, 32, 23 participants) and one expert (10 participants) subgroups undertook an ultrasound simulation training session. Pre- and post-training test scores were collected for each subgroup. Outcome measures were as follows: mean accuracy score for obtaining the correct anatomical plane, percentage of correctly acquired target planes, mean number of movements, time to achieve image, distance travelled by probe and accumulated angling of the probe.

Results

The novices showed improvement in image acquisition after completion of the simulation training session with an improvement in the rate of correctly acquired target planes from 28-57% to 39-83%. This was not replicated in the experts. The novice's individual ratios based on pre- vs. post-training metrics improved between 1.7- and 4.3-fold for number of movements, 1.9- and 6.7-fold for distance, 2.0- and 5.2-fold for time taken and 1.8- and 7.3-fold for accumulated angling. Among the experts, there was no relationship between pre-training simulator metrics and years of ultrasound experience.

Conclusions

The individual simulation metrics suggest the sessions were delivered at an appropriate level for basic training as novice trainees were able to show demonstrable improvements in both efficiency and accuracy on the simulator. Experts did not improve after the simulation modules, and the novice scores post-training were similar to those of experts, suggesting the exercises were valid in testing ultrasound skills at novice but not expert level.

Multicenter randomized trial exploring effects of simulation-based ultrasound training on obstetricians' diagnostic accuracy: value for experienced operators

OBJECTIVE

To explore the effects of simulation-based ultrasound training on the accuracy of fetal weight estimation in the third trimester among obstetricians with different levels of clinical experience.

METHODS

This was a multicenter, randomized pre-post-test practical trial conducted between March 2016 and January 2018. Obstetricians with different levels of clinical experience were randomized to either simulation-based ultrasound training focusing on fetal weight scans or no intervention. Participants completed two scans in pregnant women at term to establish baseline accuracy of fetal weight estimation. Another two scans were performed at follow-up. Accuracy was defined by the percentage difference between estimated fetal weight and actual birth weight. Ultrasound image quality was rated by two expert raters.

RESULTS

Seventy participants with different levels of clinical experience completed the study. Adjusting for clinical experience, the intervention group demonstrated an improvement in measurement accuracy of 31.9% (95% CI, 6.9-50.1%) (P = 0.02), whereas the control group did not improve (relative difference, 13.1% (95% CI, -17.9 to 55.9%); P = 0.45). The change in accuracy was significantly different between the groups (P = 0.02) and independent of clinical experience (P = 0.54). Image-quality scores improved by a mean of 1.2 (95% CI, 0.4-2.1) (P < 0.01) in the intervention group, with no change in the control group (mean difference, 0.1 (95% CI, -0.8 to 1.0); P = 0.78). There was a strong negative correlation between time spent using the simulator and clinical experience (r = -0.70, P = 0.0001).

CONCLUSION

Simulation-based ultrasound training improved accuracy and image quality when performing fetal weight estimation in women at term, independent of obstetricians' clinical experience. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

Fetal biometry for guiding the medical management of women with gestational diabetes mellitus for improving maternal and perinatal health

BACKGROUND

Gestational diabetes mellitus (GDM) is a common medical condition that complicates pregnancy and causes adverse maternal and fetal outcomes. At present, most treatment strategies focus on normalisation of maternal blood glucose values with use of diet, lifestyle modification, exercise, oral anti-hyperglycaemics and insulin. This has been shown to reduce the incidence of adverse outcomes, such as birth trauma and macrosomia. However, this involves intensive monitoring and treatment of all women with GDM. We propose that using medical imaging to identify pregnancies displaying signs of being affected by GDM could help to target management, allowing low-risk women to be spared excessive intervention, and facilitating better resource allocation.

OBJECTIVES

We wanted to address the following question: in women with gestational diabetes, does the use of fetal imaging plus maternal blood glucose concentration to indicate the need for medical management compared with glucose concentration alone reduce the risk of adverse perinatal outcomes?

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register (29 January 2019), ClinicalTrials.gov, the World Health Organization International Clinical Trials Registry Platform (ICTRP) (both on 29 January 2019), and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials, including those published in abstract form only. Studies using a cluster-randomised design and quasi-randomised controlled trials were both eligible for inclusion, but we didn't identify any. Cross-over trials were not eligible for inclusion in our review.We included women carrying singleton pregnancies who were diagnosed with GDM, as defined by the trials' authors. The intervention of interest was the use of fetal biometry on imaging methods in addition to maternal glycaemic values for indicating the use of medical therapy for GDM. The control group was the use of maternal glycaemic values alone for indicating the use of such therapy.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed trials for inclusion and assessed risk of bias. Two review authors extracted data and checked them for accuracy.

MAIN RESULTS

Three randomised controlled trials met the inclusion criteria for our systematic review - the studies randomised a total of 524 women.We assessed the three included studies as being at a low to moderate risk of bias; the nature of the intervention made it difficult to achieve blinding of participants and personnel and none of the trial reports contained information about methods of allocation concealment (and were therefore assessed as being at an unclear risk of selection bias).In all studies, the intervention was the use of fetal biometry on ultrasound to identify fetuses displaying signs of fetal macrosomia, and the use of this information to indicate the use of medical anti-hyperglycaemic treatments. Those pregnancies were subject to more stringent blood glucose targets than those without signs of fetal macrosomia.Maternal outcomesThe use of fetal biometry in addition to maternal blood glucose concentration (compared with maternal blood glucose concentration alone) may make little or no difference to the incidence of caesarean delivery (risk ratio (RR) 0.81, 95% confidence interval (CI) 0.59 to 1.10; 2 trials, 428 women; low-certainty evidence). We are unclear about the results for hypertensive disorders of pregnancy (RR 0.80, 95% CI 0.34 to 1.89; 2 trials, 325 women) due to very low-certainty evidence. The included trials did not report on development of type 2 diabetes in the mother or maternal hypoglycaemia.Fetal and neonatal outcomesThe use of fetal biometry may make little or no difference to the incidence of neonatal hypoglycaemia (RR 0.90, 95% CI 0.57 to 1.42; 3 trials, 524 women; low-certainty evidence). Very low-certainty evidence means that we are unclear about the results for large-for-gestational age (RR 0.81, 95% CI 0.38 to 1.74; 3 trials, 524 women); shoulder dystocia (RR 0.33, 95% CI 0.01 to 7.98; 1 trial, 96 women); a composite measure of perinatal morbidity or mortality (RR 1.00, 95% CI 0.21 to 4.71; 1 study, 96 women); or perinatal mortality (RR 0.33, 95% CI 0.01 to 7.98; 1 trial, 96 women).

AUTHORS' CONCLUSIONS

This review is based on evidence from three trials involving 524 women. The trials did not report some important outcomes of interest to this review, and the majority of our secondary outcomes were also unreported. The available evidence ranged from low- to very low-certainty, with downgrading decisions based on limitations in study design, imprecision and inconsistency.There is insufficient evidence to evaluate the use of fetal biometry (in addition to maternal blood glucose concentration values) to assist in guiding the medical management of GDM, on either maternal or perinatal health outcomes, or the associated costs.More research is required, ideally larger randomised studies which report the maternal and infant short- and long-term outcomes listed in this review, as well as those outcomes relating to financial and resource implications.

Concordance Rates Between Resident-Performed Ultrasound Measurements and Certified Sonographer Measurements

OBJECTIVES

To evaluate the accuracy of ultrasound (US) estimated fetal weight (EFW) measurement compared with neonatal birth weight when performed by residents versus certified sonographers. The hypothesis tested was that residents and certified sonographers would not differ significantly in EFW or in EFW compared with neonatal birth weight.

METHODS

A retrospective chart review of 142 inpatients from July 2010 to May 2011 was conducted. Ultrasound examinations were performed by a resident physician and a certified sonographer within 7 days after the resident. Standard US measurements obtained were head circumference, biparietal diameter, abdominal circumference, femur length, estimated gestational age, and EFW. Gestational age ranged from 20 to 39 weeks. The time from US to delivery, residency year, and birth weight were collected. Measurements were compared by paired t tests, the Wilcoxon signed rank test, and repeated-measures analysis of variance.

RESULTS

The US EFW by residents and sonographers showed excellent concordance with each other regardless of the neonatal birth weight. The resident and sonographer EFW each showed excellent concordance with the neonatal birth weight, and this concordance did not differ significantly between residents and sonographers for neonates weighing less than 1000 g (P = .61) and neonates weighing greater than or equal to 1000 to less than 2000 g (P = .93). The resident EFW (P < .05) and sonographer EFW (P < .01), however, were less than the neonatal birth weight for larger neonates (≥2000 g), but the degree of underestimation was not significantly different between residents and sonographers (P = .51).

CONCLUSIONS

Accurate EFW is critical for prenatal management. These data support the value of a dedicated month of US training in residency programs.

Influence of maternal obesity on the accuracy of ultrasonography birth weight prediction

Objective: The aim of the study was to investigate whether the accuracy of ultrasound estimates of fetal weight (EFW) was dependent on maternal obesity.Study design: A prospective cross-sectional study of 1064 singleton pregnant women classified according to body mass index (BMI) into two categories: normal (BMI < 25 kg/m², n = 863) and obese (BMI ≥ 35 kg/m², n = 201) was conducted. EFW were calculated using Hadlock's formula, and the difference between EFW and the actual birthweight (absolute percent error) was analyzed in both groups. Spearman's correlation was used to assess the relationship between ultrasound performance (absolute error), maternal BMI, and actual birth weight.Results: Median absolute error of sonographic EFW was 5.90 and 6.47% for the normal and obese groups, respectively (p .38). A correlation between EFW and birth weight (BW) was found in both groups, r = 0.755 (p < .001) and r = 0.753 (p < .001), respectively. The correlation between absolute error, maternal BMI, and fetal birth weight was poor.Conclusions: Maternal obesity is unrelated to the accuracy of sonographic EFW, and regardless of maternal or fetal size, ultrasound is currently an accurate method of prediction for both obese and normal weight pregnant women.

Accuracy of sonographic fetal weight estimation in full-term singleton pregnant women

OBJECTIVES

To investigate the factors which might influence the sonographic fetal weight estimation (SFWE) accuracy.

METHODS

This prospective study was conducted among 949 singleton term pregnant women who delivered at a tertiary center, from January 2017 to December 2017. All participants' maternal (i.e. parity, age, body mass index and gestational weight gain during pregnancy), fetal sonographic (i.e. fetal presentation, amniotic fluid index, localization of placenta and estimated fetal weight) and neonatal (birth weight and gender) characteristics were recorded. A p<0.05 was considered significant.

RESULTS

The mean absolute percent error (APE) values of SFWE was 8.2±6.5 percent, and overall failure ratio (APE >10%) was 33%. In failure group, primiparous woman and cephalic presentation fetus were significantly more common compared to accuracy group (55.9% vs.44.8%; p=0.001 and 98% vs. 95.2%; p=0.03, respectively). In contrast, the mean neonatal birth weight (NBW) value was significantly lower in failure group compared to success group (3250±565 gr vs. 3404±410 gr; p=0.001). The correlation between SFWE and NBW was linear, however negative, and significant (p=0.001). Logistic regression analysis revealed that primiparous woman, cephalic presentation fetus and <3300 gr NBW were independent risk factors for the SFWE failure (relative risks were 1.6, 2.8 and 2.4 respectively, p<0.05).

CONCLUSION

SFWE has a high correlation with NBW, however it's accuracy is still unsatisfactory, and depend on many unpredictable and inconsistent factors.

Ultrasound versus Clinical Examination to Estimate Fetal Weight at Term

Introduction At term, fetal weight estimation is an important factor for decisions about the delivery mode and the timing of labor induction. This study aimed to compare the accuracy of abdominal palpation with that of ultrasound performed by different examiners to estimate fetal weight. The study investigated whether differences in the examiners' training affected fetal weight estimates. The accuracy of the weight estimates made for fetuses with extreme birth weights was also evaluated. Finally, the accuracy of Johnson's method and of Insler and Bernstein's formula for estimating fetal weight were compared with the other two methods. Methods This prospective study included singleton pregnancies between 37 weeks of gestation and 12 days post-term planned for vaginal delivery or cesarean section. Ultrasound and abdominal palpation using Leopold's maneuvers were performed by examiners with different levels of professional experience. Fetal weight was additionally estimated using Insler and Bernstein's formula and Johnson's method. Statistical analysis calculated the accuracy of fetal weight estimates for the different examiners and the four methods. Results A total of 204 women were included in the analysis. Trained ultrasound examiners were most accurate when estimating fetal weight compared with all other examiners. The comparison of all four methods showed that fetal weight was assessed most accurately with ultrasound. No learning curve could be established. BMI and advanced gestational age affected the accuracy of the estimated weight. The analysis showed that a greater deviation between estimated weight and actual weight occurred with all four methods for fetuses at either end of the extremes of fetal weight, i.e., with very low or very high birth weights. Conclusion Fetal weight should be estimated using ultrasound. A good ultrasound training is essential.

Longitudinal Assessment of Examiner Experience and the Accuracy of Sonographic Fetal Weight Estimation at Term

OBJECTIVES

To evaluate the influence of examiner experience on the accuracy of sonographic weight estimation and to further analyze examiners' individual learning curves.

METHODS

In this multicenter study, 4613 sonographic weight estimations performed by 18 examiners at the beginning of their ultrasound training were included. To assess the effect of experience on the accuracy of weight estimation, a multivariable mixed regression model analysis was performed, with percentage error and absolute percentage error as outcome variables and the examiner, the examiner's experience (number of examinations), birth weight, gestational age, scan-to-delivery interval, and maternal body mass index as fixed effects and the perinatal center as random intercepts. To further analyze the individual learning curves of the examiners, the cumulative summation technique was used.

RESULTS

Regression analyses showed a significant influence of the number of examinations on the accuracy of sonographic weight estimation after adjustment for the above-mentioned parameters (P < .001). A typical learning curve with improving accuracy was found until approximately 200 examinations. Between 200 and 300 examinations, the diagnostic performance started to deteriorate again, with a continuous decrease until the end of the study period. Cumulative summation charts representing individual learning curves varied greatly between different examiners.

CONCLUSIONS

These findings indicate the great importance of continuous quality control systems in sonographic weight estimation.

The Effect of Amniotic Fluid Index on the Accuracy of Sonographic Estimated Fetal Weight

The objective of this study was to investigate whether there is a relationship between the amniotic fluid index (AFI) and the accuracy of the sonographic estimated fetal weight (EFW) as substantiated by the actual birth weight. This is a retrospective study where data of the sonographic estimated fetal weight and the birth weight at delivery were collected to calculate range of error when the amniotic fluid index was indicative of polyhydramnios or oligohydramnios, with normal amniotic fluid volumes as a control group. Results revealed significant, fairly strong to strong correlations between the variables within each group. Further analysis compared the mean scores of the three groups. Although differences in the mean values exist, large overlaps existed. This questions the usefulness of the correlation of the EFW and AFI in clinical use.

Ultrasound Fetal Weight Estimation: How Accurate Are We Now Under Emergency Conditions?

The primary aim of this study was to evaluate the accuracy of sonographic estimation of fetal weight when performed at due date by first-line sonographers. This was a prospective study including 500 singleton pregnancies. Ultrasound examinations were performed by residents on delivery day. Estimated fetal weights (EFWs) were calculated and compared with the corresponding birth weights. The median absolute difference between EFW and birth weight was 200 g (100-330). This difference was within ±10% in 75.2% of the cases. The median absolute percentage error was 5.53% (2.70%-10.03%). Linear regression analysis revealed a good correlation between EFW and birth weight (r = 0.79, p < 0.0001). According to Bland-Altman analysis, bias was -85.06 g (95% limits of agreement: -663.33 to 494.21). In conclusion, EFWs calculated by residents were as accurate as those calculated by experienced sonographers. Nevertheless, predictive performance remains limited, with a low sensitivity in the diagnosis of macrosomia.

Associations of maternal retinal vasculature with subsequent fetal growth and birth size

OBJECTIVE

We aimed to study the maternal retinal microvasculature at mid-trimester and its relationship with subsequent fetal growth and birth size.

METHODS

We recruited 732 pregnant women aged 18-46 years in the first trimester with singleton pregnancies. All had retinal photography and fetal scan performed at 26-28 weeks gestation, and subsequent fetal scan at 32-34 weeks gestation. Infant anthropometric measurements were done at birth. Retinal microvasculature was measured using computer software from the retinal photographs.

RESULTS

In multiple linear regression models, each 10 μm narrowing in maternal retinal arteriolar caliber was associated with decreases of 1.36 mm in fetal head circumference at 32-34 weeks gestation, as well as decreases of 1.50 mm and 2.30 mm in infant head circumference and birth length at delivery, respectively. Each standard deviation decrease in maternal retinal arteriolar fractal dimension was associated with decreases of 1.55 mm in fetal head circumference at 32-34 weeks gestation, as well as decreases of 1.08 mm and 46.42 g in infant head circumference and birth weight at delivery, respectively.

CONCLUSIONS

Narrower retinal arteriolar caliber and a sparser retinal vascular network in mothers, reflecting a suboptimal uteroplacental microvasculature during mid-pregnancy, were associated with poorer fetal growth and birth size.

[Accuracy of ultrasound estimated fetal weight performed by residents at delivery day]

Ultrasound fetal weight estimation (EFW) has become a routine practice in obstetrics with a major impact on obstetrical management.

OBJECTIVES

To evaluate the accuracy of sonographic fetal weight estimations performed by residents in obstetrics at the delivery day and to search parameters influencing this exam.

METHODS

A prospective study performed in 299 patients at 37 weeks of gestation or more, during their delivery day. Ultrasound fetal weight estimations were performed by residents and compared to birth weights (BW). The estimated fetal weight (EFW) was calculated using the formula of Hadlock: Log10 EPF=1,335+0.0316 BIP+0,0457 PA+0,1623 LF-0,0034 PA LF.

RESULTS

Mean absolute difference between EFW and BW was 200g [100-450]. Mean absolute percentage error was 5.71 % [2.7-11.37]. The proportion of the EFW within 10 % of BW was 69.6 %. There was a good correlation between EFW and BW (R=0.79). Obesity and fetal macrosomia had negatively influenced ultrasound performance. For the diagnosis of macrosomia, ultrasound has a sensibility of 38 % and a specificity of 99.59 %.

CONCLUSION

Ultrasound fetal weight estimations performed by residents in the delivery room were as accurate as those performed by experimented sonographers. Thus, the predictive performance remains limited with a low sensitivity in the diagnosis of macrosomia.

Does the level of amniotic fluid have an effect on the accuracy of sonographic estimated fetal weight at term?

OBJECTIVE

Controversy exists concerning the impact of amniotic fluid index (AFI) on the accuracy of sonographic estimation of fetal weight (EFW). Thus, we aimed to evaluate whether differences in AFI has an influence on the accuracy of sonographic EFW.

METHODS

All term, singleton pregnancies which underwent a sonographic EFW and measurement of AFI within a week from delivery were included. Cases were stratified into three categories according to AFI: (1) Normal AFI (51-249 mm), (2) Oligohydramnios (AFI ≤ 50 mm) and (3) Polyhydramnios (AFI ≥ 250 mm). Inaccurate EFW was defined if there was more than 15% difference between sonographic EFW and actual birthweight.

RESULTS

Overall, 1746 pregnancies were identified (1096 with normal AFI, 455 with oligohydramnios and 195 with polyhydramnios). Mean AFI was 115.8 ± 60 mm, 28.1 ± 13 mm and 293 ± 35 mm, p < 0.001, and mean sonographic EFW was 3182.5 ± 573 g, 3118.8 ± 517 g and 3713.2 ± 461 g, p < 0.001, respectively. Demographic data and gestational age at delivery were similar. Mean birthweight was 3221.7 ± 535 g, 3132.5 ± 505 g and 3654.1 ± 480 g, p < 0.001, respectively. The rate of inaccurate EFW was similar between the groups (8.4%, 8.7% and 9.7%, p = 0.19, respectively). On multivariate analysis, AFI was not associated with EFW inaccuracy (OR 1.01, 95% C.I 0.67-1.54, p = 0.93).

CONCLUSION

AFI has limited impact on the percentage of errors in sonographic fetal weight estimation a week prior delivery.

Sonographic fetal weight estimation - is there more to it than just fetal measurements?

OBJECTIVES

The primary aim of this study was to evaluate the effects of different maternal, fetal, and examiner related factors on the accuracy of sonographic fetal weight estimation (SFWE).

METHODS

A retrospective cohort study analyzing 9064 SFWEs performed within 1 week prior to delivery, including singleton pregnancies with a gestational age of 37 to 42 weeks, was recorded at one medical center from January 2004 to September 2011. Predicted birth weights were calculated according to models by Sabbagha et al., Hadlock et al., and Combs et al. and were compared with the actual birth weight. Effects of different factors on SFWE accuracy were assessed. The systematic error, random error, and mean absolute percentage error were used as measures of accuracy.

RESULTS

High maternal weight, height, body mass index, multiparity, older maternal age, diabetes, and fetal male sex were associated with underestimation of SFWE (P < 0.05). Fetal presentation and the sonographer's experience influenced SFWE differently using various models. The amniotic fluid index did have a significant effect on SFWE. Overall, more than 90% of the systematic errors were unaccounted for in the factors we assessed.

CONCLUSIONS

Many maternal and fetal factors significantly influence the SFWE; nevertheless, most errors are probably due to inherent problems in SFWE formulas.

Prediction of newborn birth weight based on the estimation at 20-24 weeks of gestation

OBJECTIVE

The aim of this study was to develop a mathematical equation to predict the birth weight during the second trimester at 20-24 weeks of gestation.

MATERIALS AND METHODS

In a university hospital, 110 healthy pregnant women were eligible for inclusion at 20-24 weeks of gestation. We recorded the maternal weight (pre-pregnancy, mid-pregnancy, and at delivery) and body mass index (BMI), newborn birth weight, time period from ultrasound examination to term delivery, and also the fetal biometrics sonographically at 20-24 weeks of gestation. Pearson's correlation was used to verify the extent of the relationship between all the above measurements and the newborn birth weight. Multiple regressions with the stepwise method were used to analyze maternal weight factors, fetal biometrical factors, and pregnancy interval. An equation for term birth weight estimation during the second trimester was determined.

RESULTS

Maternal BMI at mid-pregnancy, time interval from mid-pregnancy to term, and abdominal circumference had the highest correlation with newborn birth weight (r = 0.388, 0.341, and 0.315, respectively, p < 0.05). Using the stepwise regression analysis, an optimal formula with variance of 0.303 was derived: estimated birth weight = -700 + 49.766 × (mid-pregnancy BMI [kg/m2]) + 13.362 × (time interval from mid-pregnancy to term delivery [days]) + 68.696 × (abdominal circumference [cm]).

CONCLUSION

We propose an accurate, simple, and easy formula to better assess the newborn birth weight at mid-pregnancy for the Asian population. Mid-pregnancy BMI was a more significant factor for birth weight estimation than other maternal weight factors in this study.

Clinical estimation of fetal weight: is accuracy acquired with professional experience?

OBJECTIVE

This study was conducted in order to determine whether experience and type of obstetrical profession improves the accuracy in the clinical estimation of fetal weight among obstetricians and midwives in the delivery room.

METHODS

Four groups of professionals in the delivery room clinically estimated the fetal weight in 236 parturients in active labor. Obstetric parameters such as gravidity, parity, gestational age, body mass index, amniotomy, station and cervical dilatation were recorded. Fetal weight estimations were compared with the actual birth weight after delivery.

RESULTS

The mean error rate of fetal weight estimation by attending obstetricians, residents, experienced and junior midwives was 7.9 ± 8.8, 8.0 ± 8.4, 7.8 ± 6.3 and 8.5 ± 6.8%, respectively. Error rates of the 4 groups of examiners were similar, although it was increased in all subgroups when estimating birth weights <2,500 and >4,000 g. Major discrepancies of fetal weight estimation (>10% of the actual fetal birth weight) occurred in 27.2, 28.9, 31.9 and 34.7% by attending obstetricians, residents, experienced and junior midwives, respectively.

CONCLUSIONS

We found no additional value for experience and type of obstetrical training in the accuracy of clinical fetal weight estimation.

Continuous independent quality control for fetal ultrasound biometry provided by the cumulative summation technique

OBJECTIVE

To apply the cumulative summation (CUSUM) technique for an evaluation of the learning process of sonographic fetal weight estimation at term in combination with the z-scores of biometry determinants and to assess the time of appearance and sources of errors.

METHODS

Learning curve (LC-CUSUM) and double CUSUM charts for systematic error detection based on absolute and signed mean percentage error were generated to retrospectively estimate the longitudinal accuracy of sonographic fetal weight estimation conducted by three trainees and one experienced examiner. For LC-CUSUM analysis an examination was considered to be a failure when there was an absolute error in birth weight estimation >/= 15%. Fetal biometry measurements (head circumference, abdominal circumference (AC) and femur length (FL)) from 227 routine ultrasound scans of one examiner were separately transformed into z-scores and double CUSUM charts were generated to assess the systematic errors for each determinant.

RESULTS

The LC-CUSUM charts revealed that different numbers of scans are required for different examiners to achieve competence in estimating birth weight. AC and FL deviated most significantly from expected values (P < 0.05). The double CUSUM charts revealed exact periods of systematic errors in the measurement of biometry determinants, clearly reflecting errors of fetal weight estimation.

CONCLUSIONS

The use of CUSUM techniques in the analysis of sonographic data allows observation of the development of an examiner's skill and maintenance of competence. The CUSUM technique not only allows the reasons for impaired fetal weight estimation to be revealed but also allows determination of the exact time when inaccurate measurements start to occur. We suggest that CUSUM charts should be implemented in routine clinical practice as a measure of objective quality evaluation of sonographic fetal biometry.

A review of sonographic estimate of fetal weight: Vagaries of accuracy

PURPOSE

To determine the factors that might influence the accuracy of sonographic estimated fetal weight.

STUDY DESIGN

A PubMed search (Jan 1975 to Jan 2003) of articles published in the English language was carried out and the inclusion criterion was that estimates were within 10% of birth weight. A Chi-square test for trend was used and odds ratio (OR) with 95% confidence intervals (CI) was calculated.

RESULTS

Over 28 years, 175 articles were identified but only 54 (31%) met the inclusion criterion. Overall 62% (8895/14 384) of the predictions were within 10% of the actual weight. The accuracy was significantly different in articles where <7 vs. >7 days were allowed to lapse between examination and delivery (OR 2.17, 95% CI 1.93, 2.45); where examinations were done by registered diagnostic medical sonographers (RDMS; 65%) versus physicians (59%) or residents (57%; p < 0.0001); in term vs. preterm patients (OR 1.97, 95% CI 1.67, 2.13); and in studies with >1000 vs. <1000 cohorts (OR 1.62; 95% CI 1.51, 1.74).

CONCLUSIONS

If feasible the sonographic examination should be done by RDMS and within a week of delivery.

Management of gestational diabetes mellitus

The incidence of gestational diabetes mellitus (GDM) is on the increase and, if not diagnosed, managed and treated adequately, can have unfavorable maternal and fetal outcomes. Several studies have shown that glycemic values considered as adequate in the past when monitoring GDM failed to contain these adverse outcomes and randomized trials are needed to ascertain whether these targets should be lowered. Dietary restrictions remain the mainstay of GDM management and suitable physical exercise can help too. The use of rapid-acting insulin analogues (lispro and aspart) are novel treatments for improving metabolic control by reducing postprandial glycemia, while long-acting insulin analogues need to be evaluated by further studies for safety in clinical use before they can be prescribed. Numerous studies have found glyburide and metformin safe in women with GDM but more randomized controlled trials are needed, with a long-term follow-up of mother and child, to confirm these results.

Analysis of factors influencing the ultrasonic fetal weight estimation

OBJECTIVE

The aim of our study was the evaluation of sonographic fetal weight estimation taking into consideration 9 of the most important factors of influence on the precision of the estimation.

METHODS

We analyzed 820 singleton pregnancies from 22 to 42 weeks of gestational age. We evaluated 9 different factors that potentially influence the precision of sonographic weight estimation (time interval between estimation and delivery, experts vs. less experienced investigator, fetal gender, gestational age, fetal weight, maternal BMI, amniotic fluid index, presentation of the fetus, location of the placenta). Finally, we compared the results of the fetal weight estimation of the fetuses with poor scanning conditions to those presenting good scanning conditions.

RESULTS

Of the 9 evaluated factors that may influence accuracy of fetal weight estimation, only a short interval between sonographic weight estimation and delivery (0-7 vs. 8-14 days) had a statistically significant impact.

CONCLUSION

Of all known factors of influence, only a time interval of more than 7 days between estimation and delivery had a negative impact on the estimation.

Estimation of birth weight by two-dimensional ultrasonography: a critical appraisal of its accuracy

OBJECTIVE

To assess the accuracy and characterize two-dimensional ultrasonographic formulas for the estimation of birth weight according to the type of fetal biometric parameters these formulas rely on to make fetal weight predictions.

METHODS

A prospective recruitment of 589 pregnant women was carried out for this cross-sectional study. Different biometric parameters were taken ultrasonographically to estimate birth weight using 35 different formulas. Only those patients who delivered within 48 hours were considered for the analysis (n=441). Differences between the estimated and actual birth weight were assessed by percentage error, accuracy in predictions within +/-10% and +/-15% of error, and use of the Bland-Altman method. All formulas were assessed individually and clustered on the basis of the type of fetal biometric information that they incorporate.

RESULTS

Twenty-nine formulas provided an overall mean absolute percentage error less than or equal to 10%, with overall predictions within +/-10% and +/-15% of the actual birth weight (69.2% and 86.5%, respectively). Twenty formulas showed a good accuracy (bias 0.50 or less) and low variability (mean standard deviation 1.2). Among the categorized algorithms, formulas based on head-abdomen-femur measurements showed the lowest mean absolute percentage error. Upon stratification for birth weight, the group of formulas that rely on abdomen and femur measurements performed best for fetuses weighing more than 3,500 g (P<.01).

CONCLUSION

Our findings show that most formulas are relatively accurate at predicting birth weight up to 3,500 g, and all algorithms tend to underestimate large fetuses.

LEVEL OF EVIDENCE

III.

Clinical and ultrasound estimation of birth weight prior to induction of labor at term

OBJECTIVES

To assess and compare the accuracy of clinical and sonographic fetal weight estimation in predicting birth weight prior to induction of labor.

METHODS

In a prospective study of 262 women immediately prior to induction of labor, the fetal weight was estimated clinically by both the doctor (DR EFW) and the woman herself (WM EFW). A transabdominal scan was then performed to estimate the fetal weight sonographically using two different formulae-Shepard (SHEP EFW) and Hadlock (HAD EFW). The four estimated fetal weights were compared with the actual birth weight.

RESULTS

The mean percentage error was - 1.9 +/- 9.3% for DR EFW, - 3.4 +/- 12.6% for WM EFW, - 2.3 +/- 11.6% for SHEP EFW and - 7.6 +/- 10.6% for HAD EFW. All four EFWs were significantly different from birth weight (t = - 4.7, - 5.5, - 3.5 and - 11.4, respectively, all P < 0.01). The corresponding proportion of the EFWs which were within 10% of birth weight were 71%, 59%, 62% and 42%, respectively. The sensitivity and specificity of detecting a fetus weighing < 3000 g were 56% and 98% for DR EFW, 90% and 89% for WM EFW, 93% and 83% for SHEP EFW and 100% and 76% for HAD EFW. The corresponding values for detecting a fetus weighing > 4000 g were 16% and 99%, 29% and 96%, 48% and 92% and 40% and 94%, respectively.

CONCLUSIONS

Although, in general, clinical estimates of birth weight perform favorably compared with ultrasonographic estimates, ultrasound immediately prior to labor is more accurate at predicting the low- or high-birth-weight fetus.

Prévention de la dystocie des épaules par la sélection échographique en début de travail des fœtus à fort périmètre abdominal

OBJECTIVE

Prevent shoulder dystocia occuring with macrosomic foetuses, by an ultrasound screening, at the beginning of labour, made by a member of obstetrics staff.

MATERIAL AND METHOD

A prospective study in the maternity hospital, la Mère et l'Enfant of University Teaching Hospital, Besançon, about 170 patients. We have measured only one parameter: the foetal abdominal circumference (AC).

RESULTS

An AC>or=350 mm had a sensitivity of 100% to detect newborns of birth weight>or=4250 g.

CONCLUSION

An AC>or=350 mm measured during labour by a member of obstetrics staff allow to alert and to make the staff sensitive to a risk of macrosomia and shoulder dystocia.

Does Hands-on Obstetric US Experience Improve Performance on the Radiology Oral Board Examination?

PURPOSE

To investigate whether the inclusion of hands-on obstetric ultrasonography (US) experience as a formal part of radiology residency affects performance on the US section of the oral board examination.

MATERIALS AND METHODS

An electronic survey was sent to all radiology residency programs to assess (a) the time assigned to US rotation, (b) the inclusion of obstetrics in US rotation, and (c) the opportunity for hands-on scanning of obstetric patients. Blinded results from the 2002 Diagnostic Radiology Oral Board Examination were provided by the American Board of Radiology. We recorded the overall examination score, US section score, and individual score for all obstetric cases for each resident from programs that responded to the survey. A Student t test and stratified statistical analyses were performed. This study was determined to be exempt from institutional review board approval. Residency directors who consented to participate were informed of pertinent information.

RESULTS

Of the 159 programs, 64 (40.3%) responded and 63 (98%) of these had scores available. US section scores were provided for 280 residents, with 869 obstetric case scores. Fifty (79%) of 63 programs provided the opportunity for hands-on obstetric scanning. After adjusting for covariates, there was no significant difference in individual resident performance between residents with hands-on scanning experience and those without hands-on scanning experience (P = .61). When evaluated according to program, there was no significant difference in performance between programs with and those without hands-on training (P = .39).

CONCLUSION

Radiology resident performance in obstetric US on the American Board of Radiology Oral Board Examination is similar for programs that provide the opportunity for hands-on obstetric scanning compared with those that do not.

Accuracy of estimated fetal weight in shoulder dystocia and neonatal birth injury

OBJECTIVE

This study was undertaken to determine whether there is any difference in the rate of error of estimated fetal weight (EFW) in cases of shoulder dystocia compared with controls.

STUDY DESIGN

Women whose delivery was complicated by shoulder dystocia were studied and compared with a control group matched for parity, race, labor type (spontaneous or induced), and birth weight (BW). Accuracy (%) was defined as [(EFW-BW)/BW] x 100. The primary outcome of the study was rate of EFW underestimation error 20% or greater.

RESULTS

During the 5-year study period, there were 206 cases of shoulder dystocia that met all study criteria. There was no difference in the number of patients that had EFW underestimation error 20% or greater (shoulder dystocia 9.8% vs control 12.8%; P = .38). There was also no difference in the number of patients that had EFW underestimation error 20% or greater between shoulder dystocia with and without injury (injury 8.3% vs no injury 7.1%; P = .79).

CONCLUSION

EFW underestimation error in cases of shoulder dystocia is an infrequent event and does not occur more often than in deliveries without shoulder dystocia.

Clinical and sonographic estimation of fetal weight performed during labor by residents

OBJECTIVE

This study was undertaken to assess the accuracy of both clinical and sonographic estimations of the fetal weight (EFW) performed during the active phase of labor by residents.

METHODS

The study protocol consisted of achieving clinical, followed by sonographic EFW by the admitting resident during the active phase of labor. Patients who had an EFW (clinical or sonographic) within the last 2 weeks were excluded from the study. In addition, the effect of the following variables on the accuracy of the EFW were examined: maternal age, maternal weight and body mass index, parity, the Bishop score before obtaining the EFW, gestational age, birth weight, and the postgraduate year of the examiner. The Pearson correlation, chi2 test, and Student t test were the statistical analyses used. We also calculated the sensitivity, specificity, and positive and negative predictive values for clinical and sonographic EFW for detecting macrosomia (birth weight > or = 4000 g).

RESULTS

A total of 192 patients participated in this study. The coefficient of correlation between the clinical and sonographic EFW and the actual birth weight was 0.59 (P < .0001) and 0.65 (P < .0001), respectively. Clinical EFW was correct (within +/-10%) in 72% of the cases and the sonographic EFW was correct (within +/-10%) in 74% of the cases. However, the sensitivity of predicting birth weight of 4 kg or more was only 50% for both clinical and sonographic EFW, with 95% and 97% specificity, respectively. None of the clinical variables that were tested were significantly associated with the accuracy of the EFW.

CONCLUSION

Both clinical and sonographic EFW performed during the active phase of labor by residents correlate with the actual birth weight but have poor sensitivity in detecting macrosomic fetuses. Sonographic EFWs offer no advantage over clinical EFWs.

A systematic review of the ultrasound estimation of fetal weight

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.

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

AIMS

To evaluate the accuracy of sonographic estimation of fetal weight (EFW) in diabetic pregnancies and pregnancies with suspected fetal macrosomia.

METHODS

63 women with diabetic pregnancies, 74 nondiabetic women with suspected large-for-gestational-age (LGA) infants, and 161 controls underwent ultrasound assessment prior to induction of labor. EFW was compared to the weight at birth, 1-3 days later.

RESULTS

EFW was highly correlated to birth weight. Absolute or actual weight differences between the birth weight and the EFW, and the rate of EFW within 10% of birth weight were not different between the groups. A linear regression model controlling for maternal and gestational age, diagnosis of gestational or pregestational diabetes, birth weight, gravidity, parity, nulliparity, placental location and AFI was not significantly correlated to the absolute or actual weight differences. In pregnancies with suspected LGA, higher birth weight was an independent and significant predictor of high weight difference inaccuracy.

CONCLUSIONS

The ultrasonographic EFW 1-3 days before delivery is highly correlated with birth weight, reaffirming the clinical use of abdominal circumference and femur length in estimating fetal weight near labor at term. In pregnancies with suspected LGA fetuses and higher prevalence of macrosomia, ultrasound has higher sensitivity but lower specificity than the controls.