Accuracy of antenatal ultrasound in predicting large-for-gestational-age babies: population-based cohort study.

BACKGROUND: Pregnancies with large-for-gestational-age fetuses are at increased risk of adverse maternal and neonatal outcomes. There is uncertainty about how to manage birth in such pregnancies. Current guidelines recommend a discussion with women of the pros and cons of options, including expectant management, induction of labor, and cesarean delivery. For women to make an informed decision about birth, antenatal detection of large for gestational age is essential. OBJECTIVE: To investigate the ability of antenatal ultrasound scans to predict large for gestational age at birth. STUDY DESIGN: In this retrospective cohort study, we analyzed data from a routinely collected database from the West Midlands, United Kingdom. We included pregnancies that had an antenatal ultrasound-estimated fetal weight between 35+0 and 38+0 weeks gestation for any indication and a subgroup where the reason for the scan was that the fetus was suspected to be big. Large for gestational age was defined as >90th customized GROW percentile for estimated fetal weight as well as neonatal weight. In addition, we tested the performance of an uncustomized standard, with Hadlock fetal weight >90th percentile and neonatal weight >4 kg. We calculated diagnostic characteristics for the whole population and groups with different maternal body mass indexes. RESULTS: The study cohort consisted of 26,527 pregnancies, which, on average, had a scan at 36+4 weeks gestation and delivered 20 days later at a median of 39+3 weeks (interquartile range 15). In total, 2241 (8.4%) of neonates were large for gestational age by customized percentiles, of which 1459 (65.1%) had a scan estimated fetal weight >90th percentile, with a false positive rate of 8.6% and a positive predictive value of 41.0%. In the subgroup of 912 (3.4%) pregnancies scanned for a suspected large fetus, 293 (32.1%) babies were large for gestational age at birth, giving a positive predictive value of 50.3%, with a sensitivity of 77.1% and false positive rate of 36.0%. When comparing subgroups from low (<18.5 kg/m2) to high body mass index (>30 kg/m2), sensitivity increased from 55.6% to 67.8%, false positive rate from 5.2% to 11.5%, and positive predictive value from 32.1% to 42.3%. A total of 2585 (9.7%) babies were macrosomic (birthweight >4 kg), and of these, 1058 (40.9%) were large for gestational age (>90th percentile) antenatally by Hadlock's growth standard, with a false positive rate of 4.9% and a positive predictive value 41.0%. Analysis within subgroups showed better performance by customized than uncustomized standards for low body mass index (<18.5; diagnostic odds ratio, 23.0 vs 6.4) and high body mass index (>30; diagnostic odds ratio, 16.2 vs 8.8). CONCLUSION: Late third-trimester ultrasound estimation of fetal weight for any indication has a good ability to identify and predict large for gestational age at birth and improves with the use of a customized standard. The detection rate is better when an ultrasound is performed for a suspected large fetus but at the risk of a higher false positive diagnosis. Our results provide information for women and clinicians to aid antenatal decision-making about the birth of a fetus suspected of being large for gestational age.

Birthweight charts customised for maternal height optimises the classification of small and large-for-gestational age newborns.

AIM: To construct birthweight charts customised for maternal height and evaluate the effect of customization on SGA and LGA classification. METHODS: Data were extracted (n = 21 350) from the MiCaS project in the Netherlands (2012-2020). We constructed the MiCaS-birthweight chart customised for maternal height using Hadlock's method. We defined seven 5-centimetre height categories from 153 to 157 cm until 183-187 cm and calculated SGA and LGA prevalences for each category, using MiCaS and current Dutch birthweight charts. RESULTS: The MiCaS-chart showed substantially higher birthweight values between identical percentiles with increasing maternal height. In the Dutch birthweight chart, not customised for maternal height, the prevalence of SGA (p90) increased with increasing height category, from 1.4% in the lowest height category to 21.8% in the highest category (range 20.4%). In the MiCaS-birthweight chart, SGA and LGA prevalences were more constant across maternal heights, similar to overall prevalences (SGA range 3.3% and LGA range 1.7%). CONCLUSION: Compared to the current Dutch birthweight chart, the MiCaS-birthweight chart customised for maternal height shows a more even distribution of SGA and LGA prevalences across maternal heights.

A novel software for method comparison: MCS (method comparison software)-assessing agreement between estimated fetal weights calculated by Hadlock I-V formulas and birth weight.

INTRODUCTION: The evaluation of the performance of new methods, expected to provide cheaper and faster results than existing (reference) methods in the health field, is based on comparing the results obtained with this new method to those obtained with the existing method. The primary aim of this study is to examine the correlational and absolute agreement between measurement methods in clinical studies using Bland-Altman analysis and methodological (Ordinary Least Squares, Weighted Ordinary Least Squares, Deming, Weighted Deming, Passing-Bablok, Theil-Sen, and Passing-Bablok for Large Data Sets.) methods, and the secondary aim is to compare the accuracy and precision of Hadlock (I-V) formulas used for fetal weight estimation. MATERIALS AND METHODS: The study was conducted on singleton pregnancies examined in the Prenatal Diagnosis and Treatment Unit of the Department of Obstetrics and Gynecology at Inonu University Faculty of Medicine and who gave birth in the Obstetrics Unit between 01.01.2020 and 01.09.2023, whose gestational ages were confirmed by first-trimester ultrasonography. Estimated fetal weights were calculated using Hadlock (I-V) formulas, and the agreement of these weights with birth weight was evaluated with Bland-Altman method. RESULTS: The comparison of estimated fetal weights calculated using Hadlock formulas with birth weight was analyzed using Bland-Altman analysis, ICC, and CCC values along with regression analyses. According to the mean difference values obtained by Bland-Altman analysis, the estimated fetal birth weights obtained by the Hadlock IV formula were most consistent with the actual birth weights. CONCLUSIONS: The estimated fetal weights obtained using the Hadlock IV formula resulted in the closest measurements to the birth weight. This study showcases the efficacy of a new web-based software, Method Comparison Software (MCS), which can be utilized for evaluating the agreement between different methods in clinical measurements.

Fetal growth restriction and small for gestational age as predictors of neonatal morbidity: which growth nomogram to use?

BACKGROUND: Fetal growth nomograms were developed to screen for fetal growth restriction and guide clinical care to improve perinatal outcomes; however, existing literature remains inconclusive regarding which nomogram is the gold standard. OBJECTIVE: This study aimed to compare the ability of 4 commonly used nomograms (Hadlock, International Fetal and Newborn Growth Consortium for the 21st Century, Eunice Kennedy Shriver National Institute of Child Health and Human Development-unified standard, and World Health Organization fetal growth charts) and 1 institution-specific reference to predict small for gestational age and poor neonatal outcomes. STUDY DESIGN: This was a retrospective cohort study of all nonanomalous singleton pregnancies undergoing ultrasound at ≥20 weeks of gestation between 2013 and 2020 and delivering at a single academic center. Using random selection methods, the study sample was restricted to 1 pregnancy per patient and 1 ultrasound per pregnancy completed at ≥22 weeks of gestation. Fetal biometry data were used to calculate estimated fetal weight and percentiles according to the aforementioned 5 nomograms. Maternal and neonatal data were extracted from electronic medical records. Logistic regression was used to estimate the association between estimated fetal weight of <10th and <3rd percentiles compared with estimated fetal weight of 10th to 90th percentile as the reference group for small for gestational age and the neonatal composite outcomes (perinatal mortality, hypoxic-ischemic encephalopathy or seizures, respiratory morbidity, intraventricular hemorrhage, necrotizing enterocolitis, hyperbilirubinemia or hypoglycemia requiring neonatal intensive care unit admission, and retinopathy of prematurity). Receiver operating characteristic curve contrast estimation (primary analysis) and test characteristics were calculated for all nomograms and the prediction of small for gestational age and the neonatal composite outcomes. We restricted the sample to ultrasounds performed within 28 days of delivery; moreover, similar analyses were completed to assess the prediction of small for gestational age and neonatal composite outcomes. RESULTS: Among 10,045 participants, the proportion of fetuses classified as <10th percentile varied across nomograms from 4.9% to 9.7%. Fetuses with an estimated fetal weight of <10th percentile had an increased risk of small for gestational age (odds ratio, 9.9 [95% confidence interval, 8.5-11.5] to 12.8 [95% confidence interval, 10.9-15.0]). In addition, the estimated fetal weight of <10th and <3rd percentile was associated with increased risk of the neonatal composite outcome (odds ratio, 2.4 [95% confidence interval, 2.0-2.8] to 3.5 [95% confidence interval, 2.9-4.3] and 5.7 [95% confidence interval, 4.5-7.2] to 8.8 [95% confidence interval, 6.6-11.8], respectively). The prediction of small for gestational age with an estimated fetal weight of <10th percentile had a positive likelihood ratio of 6.3 to 8.5 and an area under the curve of 0.62 to 0.67. Similarly, the prediction of the neonatal composite outcome with an estimated fetal weight of <10th percentile had a positive likelihood ratio of 2.1 to 3.1 and an area under the curve of 0.55 to 0.57. When analyses were restricted to ultrasound within 4 weeks of delivery, among fetuses with an estimated fetal weight of <10th percentile, the risk of small for gestational age increased across all nomograms (odds ratio, 16.7 [95% confidence interval, 12.6-22.3] to 25.1 [95% confidence interval, 17.0-37.0]), and prediction improved (positive likelihood ratio, 8.3-15.0; area under the curve, 0.69-0.75). Similarly, the risk of neonatal composite outcome increased (odds ratio, 3.2 [95% confidence interval, 2.4-4.2] to 5.2 [95% confidence interval, 3.8-7.2]), and prediction marginally improved (positive likelihood ratio, 2.4-4.1; area under the curve, 0.60-0.62). Importantly, the risk of both being small for gestational age and having the neonatal composite outcome further increased (odds ratio, 21.4 [95% confidence interval, 13.6-33.6] to 28.7 (95% confidence interval, 18.6-44.3]), and the prediction of concurrent small for gestational age and neonatal composite outcome greatly improved (positive likelihood ratio, 6.0-10.0; area under the curve, 0.80-0.83). CONCLUSION: In this large cohort, Hadlock, recent fetal growth nomograms, and a local population-derived fetal growth reference performed comparably in the prediction of small for gestational age and neonatal composite outcomes.

Accuracy of the sonographic determination of estimated fetal weight in anhydramnios.

OBJECTIVE: To determine whether the presence of anhydramnios significantly influences the sonographic estimated fetal weight (EFW) compared to a matched cohort with normal amniotic fluid volume. METHODS: The study sample of this retrospective case-control study consisted of 114 pregnant women who presented to a Tertiary Perinatal Clinic between 2015 and 2020. 57 of them presented with an anhydramnios and a matched cohort of 57 women with normal amniotic fluid volume. At time of admission, gestational age varied between 22 + 4 and 42 + 6 weeks of pregnancy. All women underwent detailed ultrasound assessment for EFW and amniotic fluid index. To determine EFW Hadlock's estimation formula I was used which is based on measurements of biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC) and femur length (FL). The EFW was compared with the weight at delivery. The maximum time interval between measurement and delivery was 5 days. RESULTS: There was neither a significant difference between the case and control group with regard to gestational age at ultrasound in days (median 249 days and 246 days, p = 0.97), nor to gestational age at birth (median 249 days and 247 days, p = 0.98). Concerning the newborns parameters, the body length at birth was not significantly different between the case and control group in centimeters (cm) (median 47 cm and 47 cm, p = 0.79). EFW in gram (g) was lower than birth weight in both groups and did not differ significantly between case and control group (estimated weight median 2247 g and 2421 g, p = 0.46; birth weight median 2440 g and 2475 g, p = 0.47). The difference between EFW and birth weight in percent (%) did not differ between the case and control group (median - 3.9% and - 5.6%, p = 0.70). The maternal parameters showed that the patients in the case group were younger (median 31 years and 38 years p = 0.20) and had a significantly higher body mass index (BMI) (median 27.3 kg/m2 vs 22.0 kg/m2, < 0.001) compared to the control group. CONCLUSION: Our study shows for the first time that EFW in women with anhydramnios can be determined sonographically just as accurately as in a matched cohort with normal amniotic fluid volume. A reliable estimation of fetal weight is crucial for optimal assessment of the newborns prognosis and counseling of the parents especially when advising women in the early weeks of pregnancy at the limit of viability.

Comparison of sonographic fetal weight estimation formulas in patients with preterm premature rupture of membranes.

BACKGROUND: Estimation of fetal weight (EFW) by ultrasound is useful in clinical decision-making. Numerous formulas for EFW have been published but have not been validated in pregnancies complicated by preterm premature rupture of membranes (PPROM). The purpose of this study is to compare the accuracy of EFW formulas in patients with PPROM, and to further evaluate the performance of the most commonly used formula - Hadlock IV. METHODS: A retrospective cohort study of women with singleton gestations and PPROM, admitted to a single tertiary center between 2005 and 2017 from 220/7-330/7 (n = 565). All women had an EFW within 14 days of delivery by standard biometry (biparietal diameter, head circumference, abdominal circumference and femur length). The accuracy of previously published 21 estimated EFW formulas was assessed by comparing the Pearson correlation with actual birth weight, and calculating the random error, systematic error, proportion of estimates within 10% of birth weight, and Euclidean distance. RESULTS: The mean gestational was 26.8 ± 2.4 weeks at admission, and 28.2 ± 2.6 weeks at delivery. Most formulas were strongly correlated with actual birth weight (r > 0.9 for 19/21 formulas). Mean systematic error was - 4.30% and mean random error was 14.5%. The highest performing formula, by the highest proportion of estimates and lowest Euclidean distance was Ott (1986), which uses abdominal and head circumferences, and femur length. However, there were minimal difference with all of the first 10 ranking formulas. The Pearson correlation coefficient for the Hadlock IV formula was strong at r = 0.935 (p < 0.001), with 319 (56.5%) of measurements falling within 10%, 408 (72.2%) within 15% and 455 (80.5%) within 20% of actual birth weight. This correlation was unaffected by gender (r = 0.936 for males, r = 0.932 for females, p < 0.001 for both) or by amniotic fluid level (r = 0.935 for mean vertical pocket < 2 cm, r = 0.943 for mean vertical pocket ≥2 cm, p < 0.001 for both). CONCLUSIONS: In women with singleton gestation and PPROM, the Ott (1986) formula for EFW was the most accurate, yet all of the top ten ranking formulas performed quite well. The commonly used Hadlock IV performed quite similarly to Ott's formula, and is acceptable to use in this specific setting.

Diagnostic accuracy of modified Hadlock formula for fetal macrosomia in women with gestational diabetes and pregnancy weight gain above recommended.

OBJECTIVES: Women with gestational diabetes (GDM) and weight gain during pregnancy above recommended more often give birth to macrosomic children. The goal of this study was to evaluate the diagnostic accuracy of the modified formula for ultrasound assessment of fetal weight created in a pilot study using a similar specimen in comparison to the Hadlock-2 formula. METHODS: This is a prospective, cohort, applicative, observational, quantitative, and analytical study, which included 213 pregnant women with a singleton pregnancy, GDM, and pregnancy weight gain above recommended. Participants were consecutively followed in the time period between July 1st, 2016, and August 31st, 2020. Ultrasound estimations were made within three days before the delivery. Fetal weights estimated using both formulas were compared to the newborns' weights. RESULTS: A total of 133 fetal weight estimations were made. In comparison to the newborns' weight modified formula had significantly smaller deviation in weight estimation compared to the Hadlock-2 formula, higher frequency of deviation within 5% of newborns weights (78.2% [95% CI=0.74-0.83] vs. 60.2%), smaller frequency of deviations from 5 to 10% (19.5 vs. 33.8%) and above 10%, which was even more significant among macrosomic children. There were 36/50 (72%) correctly diagnosed cases of macrosomia by modified and 33/50 (66%) by Hadlock-2 formula. Area under the curve (AUC) for the modified formula was 0.854 (95% CI=0.776-0.932), and for the Hadlock-2 formula 0.824 (95% CI=0.740-0.908). The positive predictive value of the modified formula was 81.81%, the negative 97.91%. CONCLUSIONS: In cases of greater fetal weights, the modified formula showed greater precision.

Role of thigh circumference in predicting the fetal weight: Comparison with other ultrasound methods-A prospective observational study.

AIM: We aimed to evaluate the addition of fetal thigh circumference (TC) to other ultrasound parameters to predict fetal weight compared to two standard formulae (Hadlock's and Vintzileos methods). METHODS: We conducted this prospective study on pregnant women between November 2018 and September 2019. The actual fetal weight was estimated within 48 h of delivery; then, it was compared to the estimated fetal weight by ultrasound. We used the Statistical Package for the Social Sciences (SPSS) software version 20.0 to perform the statistical analysis. RESULTS: A total of 123 pregnant women, with a mean age of 26.68 (5.24) years and a mean gestational age of 38.78 (0.85) weeks, were included in our study. We detected a significant positive correlation between different ultrasound parameters and actual weight (all p ≤ 0.001). The highest correlation was observed between TC and actual fetal weight (r = 0.685). Regarding both formulae, the correlation coefficient was higher in the Vintzileos formula than the Handlock formula (0.976 vs. 0.823). Our linear regression analysis showed that fetal TC could be an indicator for estimating fetal weight (p < 0.001). There was a statistically significant difference between the actual weight and the weight estimated by the Hadlock formula (p < 0.001). We detected no statistically significant difference between the estimated TC by ultrasound and the actual TC (p = 0.0602). CONCLUSION: Fetal TC can help accurately measure fetal birth weight when incorporated with other fetal parameters. The inclusion of fetal TC assessment in routine ultrasound examination is suggested to improve the birth estimates.

Comparison of clinical and ultrasonographic estimation of foetal weight at term and their correlation with birth weight.

The study compares the accuracy of clinical and ultrasonographic estimation of foetal weight at term in predicting birth weight. It was a prospective comparative study conducted in a tertiary hospital in Abuja, Nigeria between May and August 2018. Three hundred pregnant women planned for delivery were recruited. In-utero clinical estimation of foetal weight was carried out using Dare's clinical method and sonographic estimation using Hadlock 3 formula. The newborn babies were weighed within 30 minutes of delivery. The difference in the accuracy of the clinical method (75.3%) and the ultrasonographic method (82.3%) was statistically significant (p-value=0.023). The accuracy of the clinical method among parturients whose BMI were <30kg/m2 and ≥30.0kg/m2 were 83.5% and 68.5% respectively while that of the ultrasonographic method were 85.2% and 80% respectively. We conclude that ultrasonographic estimation of foetal weight is more accurate than the clinical method. However clinical method may be used when an ultrasound scan is not accessible.

Use of birth weight- vs. ultrasound-derived fetal weight classification methods: implications for detection of abnormal umbilical artery Doppler.

Objectives To compare a birth weight-derived (Brenner) and multiple ultrasound-derived [Hadlock, National Institute of Child Health and Human Development (NICHD), International Fetal and Newborn Growth Consortium (INTERGROWTH)] classification systems' frequency of assigning an antenatal estimated fetal weight (EFW) <10% and subsequent detection rate for abnormal umbilical artery Doppler (UAD). Methods We analyzed 569 consecutive non-anomalous singleton gestations identified by ultrasound with either an abdominal circumference (AC) <3% or EFW <10% at a tertiary medical center between 1/2012 and 12/2016. The biometric measurements were exported for all serial ultrasounds and the sensitivity, specificity, positive and negative predictive values, and area under the curve (AUC) were calculated for the diagnosis of any abnormal UAD, absent or reversed end-diastolic flow (AREDF), and small for gestational age (SGA) for each classification method. Results Brenner classified less patients with EFW <10% (49.7%) vs. the comparison methods (range: 84.2-85.0%; P < 0.001). The sensitivity was highest using Hadlock for detection of any abnormal UAD [96.6%; confidence interval (CI) 92.8-98.8%], AREDF (100%; CI 95.1-100%), and SGA (89.0%; CI 85.4-91.6%). However, there was minimal variation between the Hadlock, NICHD, and INTERGROWTH methods for detection of the studied outcomes. The AUCs for any abnormal UAD, AREDF, and SGA were highest for the Brenner method, but there were a substantial number of false-negative results with lower overall detection rates. Conclusions Use of a birth weight-derived method to assign a fetal weight <10% as the threshold to initiate UAD surveillance has a lower detection rate for abnormal UAD when compared to ultrasound-derived methods. Despite substantial methodological differences in the creation of the Hadlock, NICHD, and INTERGROWTH methods, there were no differences in the detection rates of abnormal UAD.

Does the Porter formula hold its promise? A weight estimation formula for macrosomic fetuses put to the test.

PURPOSE: Estimating fetal weight using ultrasound measurements is an essential task in obstetrics departments. Most of the commonly used weight estimation formulas underestimate fetal weight when the actual birthweight exceeds 4000 g. Porter et al. published a specially designed formula in an attempt to improve detection rates for such macrosomic infants. In this study, we question the usefulness of the Porter formula in clinical practice and draw attention to some critical issues concerning the derivation of specialized formulas of this type. METHODS: A retrospective cohort study was carried out, including 4654 singleton pregnancies with a birthweight ≥ 3500 g, with ultrasound examinations performed within 14 days before delivery. Fetal weight estimations derived using the Porter and Hadlock formulas were compared. RESULTS: Of the macrosomic infants, 27.08% were identified by the Hadlock formula, with a false-positive rate of 4.60%. All macrosomic fetuses were detected using the Porter formula, with a false-positive rate of 100%; 99.96% of all weight estimations using the Porter formula fell within a range of 4300 g ± 10%. The Porter formula only provides macrosomic estimates. CONCLUSIONS: The Porter formula does not succeed in distinguishing macrosomic from normal-weight fetuses. High-risk fetuses with a birthweight ≥ 4500 g in particular are not detected more precisely than with the Hadlock formula. For these reasons, we believe that the Porter formula should not be used in clinical practice. Newly derived weight estimation formulas for macrosomic fetuses must not be based solely on a macrosomic data set.

The Hadlock Method Is Superior to Newer Methods for the Prediction of the Birth Weight Percentile.

OBJECTIVES: To compare a traditional ultrasound (US) method for estimated fetal weight (EFW) calculation and fetal growth restriction diagnosis with 2 newer methods for the prediction of small for gestational age (SGA) at birth. METHODS: We reviewed deliveries at our institution from January 1, 2013, to March 31, 2017. Singleton, nonanomalous, well-dated fetuses with a US examination within 2 weeks of delivery were included. Estimated fetal weights and percentiles were calculated by a traditional method (Hadlock et al; Radiology 1991; 181:129-133) and 2 newer methods: Intergrowth-21st (INTG; Ultrasound Obstet Gynecol 2017; 49:478-486) and Salomon et al (Ultrasound Obstet Gynecol 2007; 29:550-555). We calculated each method's test characteristics to predict SGA (birth weight < 10th percentile) using both traditional (EFW < 10th percentile) and receiver operating characteristic (ROC)-derived fetal growth restriction cutoffs. Mean percentile discrepancies between EFW and birth weight measurements were calculated to compare method accuracy. We hypothesized that the INTG and Salomon methods would have superior SGA prediction compared with the Hadlock method. RESULTS: Of 831 pregnancies with a US examination within 2 weeks of delivery, 138 (16.7%) were SGA at birth. Hadlock had the smallest US-birth weight percentile discrepancy (P < .001 versus both INTG and Salomon). When comparing ROC curves, the Hadlock and INTG methods performed comparably, with areas under the curve of 0.91 and 0.90 (P = .08) and optimal EFW cutoffs of the 15th and 22nd percentiles, respectively. The Salomon method performed less well, with an area under the curve of 0.82 (P < .001 versus both Hadlock and INTG methods). CONCLUSIONS: In our study cohort, the Hadlock method predicted the birth weight percentile more accurately than the INTG or Salomon methods and performed comparably with INTG to predict SGA when ROC-derived cutoffs were used.

Comparison of the Hadlock and INTERGROWTH formulas for calculating estimated fetal weight in a preterm population in France.

BACKGROUND: Accurate estimation of fetal weight is needed for growth monitoring and decision-making in obstetrics; the INTERGROWTH project developed an estimated fetal weight formula to construct new intrauterine growth standards. OBJECTIVE: We sought to compare the accuracy of the Hadlock and INTERGROWTH formulas for the estimation of fetal weight among preterm infants. STUDY DESIGN: Using the EPIPAGE 2 population-based study of births between 22-34 weeks of gestation, we included 578 nonanomalous singleton fetuses with an ultrasound-to-delivery interval <2 days. We used abdominal circumference, head circumference, and femur length to calculate estimated fetal weight with Hadlock formula and abdominal and head circumferences to calculate estimated fetal weight according to INTERGROWTH. The mean percentage errors and the proportions of estimated fetal weight measures within ±10% of birthweight were compared between the 2 methods. RESULTS: Mean (SD) gestational age and birthweight were 29.1 (SD 2.7) weeks and 1219 (SD 489) g. Mean (SD) percentage errors for Hadlock and INTERGROWTH were significantly different: -0.7 (SD 10.1) and -3.5 (SD 11.6), respectively (P < .001), and more infants were classified within ±10% of their birthweight with Hadlock compared to INTERGROWTH (68.7% vs 57.8%, P < .001). The INTERGROWTH formula overestimated birthweight at 22-23 weeks compared to Hadlock [mean errors of 18.8 (SD 13.6) vs 5.5 (SD 10.2)] and underestimated birthweight >28 weeks: at 29-31 weeks, mean errors were -5.8 (SD 10.9) for INTERGROWTH and -0.6 (SD 10.4) for Hadlock. CONCLUSION: Hadlock estimated fetal weight formula was more accurate than INTERGROWTH formula for fetuses delivered between 22-34 weeks of gestation. Our results support continued use of Hadlock formula in France and raise questions about the applicability of INTERGROWTH intrauterine growth standards.

Comparing the Hadlock fetal growth standard to the Eunice Kennedy Shriver National Institute of Child Health and Human Development racial/ethnic standard for the prediction of neonatal morbidity and small for gestational age.

BACKGROUND: The fetal growth standard in widest use was published by Hadlock >25 years ago and was derived from a small, homogeneous cohort. In 2015, The Eunice Kennedy Shriver National Institute of Child Health and Human Development Fetal Growth Study published updated standards that are specific to race/ethnicity. These do not allow for precise estimated fetal weight percentile calculation, however, and their effectiveness to predict neonatal morbidity and small for gestational age has not yet been compared to the long-standing Hadlock standard. OBJECTIVE: We compared the ability of the Hadlock standard to predict neonatal morbidity and small for gestational age at birth with that of The Eunice Kennedy Shriver National Institute of Child Health and Human Development race-/ethnicity-specific standard. Our secondary objective was to compare their performance among our Native American population, which is not accounted for in the Eunice Kennedy Shriver National Institute of Child Health and Human Development standard. STUDY DESIGN: For this retrospective study of diagnostic accuracy, we reviewed deliveries at the University of New Mexico Hospital from Jan. 1, 2013, through March 31, 2017. We included mothers with singleton, well-dated pregnancies and nonanomalous fetuses with an estimated fetal weight within 30 days of delivery. Cubic spline interpolation was performed on the Eunice Kennedy Shriver National Institute of Child Health and Human Development estimated fetal weight-percentile tables to calculate percentiles specific to the gestational day. Estimated fetal weight percentiles were then calculated using both the Hadlock and Eunice Kennedy Shriver National Institute of Child Health and Human Development race-/ethnicity-specific standards according to maternal self-identified race/ethnicity. We calculated the receiver operator area under the curve of each method to predict composite and severe composite neonatal morbidity and small for gestational age at birth (birthweight <10th percentile). As an additional measure of method accuracy, we calculated the mean ultrasound-birthweight percentile discrepancy. For Native Americans, percentiles were calculated using the Hadlock and Eunice Kennedy Shriver National Institute of Child Health and Human Development race/ethnicity standards (white, black, Hispanic, Asian), and test characteristics were calculated for each to predict neonatal morbidity and small for gestational age. RESULTS: We included 1514 women, with a mean ultrasonography-to-delivery interval of 14.4 days (±8.8) and a small for gestational age rate of 13.6% (n = 206). For the prediction of both composite and severe composite neonatal morbidity, the Hadlock method had superior performance, with higher areas under the curve than the Eunice Kennedy Shriver National Institute of Child Health and Human Development method (P < .001 for both), though neither had good discriminatory value (all areas under the curve <0.8). For the prediction of small for gestational age at birth, the Hadlock standard had higher sensitivity (61.1%) than the Eunice Kennedy Shriver National Institute of Child Health and Human Development standard, both when using the interpolated Eunice Kennedy Shriver National Institute of Child Health and Human Development method (36.2%, P < .01) and the Eunice Kennedy Shriver National Institute of Child Health and Human Development whole-week 10th percentile cutoff (46.7%, P < .01). The Hadlock method also had a higher area under the curve than the Eunice Kennedy Shriver National Institute of Child Health and Human Development interpolated method to predict small for gestational age (0.89 vs 0.88, P < .01). The Hadlock method had a lower ultrasound-birthweight percentile discrepancy than the Eunice Kennedy Shriver National Institute of Child Health and Human Development method (6.1 vs 16.5 percentile points, P < .01). Fetuses classified as growth restricted by Hadlock but not Eunice Kennedy Shriver National Institute of Child Health and Human Development had significantly higher composite morbidity than normally grown fetuses. Among Native American women, the Hadlock method had the highest area under the curve to predict composite and severe composite morbidity, while the Hadlock and all Eunice Kennedy Shriver National Institute of Child Health and Human Development race-/ethnicity-specific methods performed comparably to predict small for gestational age. CONCLUSION: Despite its publication >25 years ago, the Hadlock standard is superior to the Eunice Kennedy Shriver National Institute of Child Health and Human Development race-/ethnicity-specific standard for the prediction of both neonatal morbidity and small for gestational age.

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

OBJECTIVES: 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. METHODS: 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. RESULTS: 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%. CONCLUSIONS: 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.

Estimating Gestational Age With Sonography: Regression-Derived Formula Versus the Fetal Biometric Average.

OBJECTIVES: To compare the accuracy of a new regression-derived formula developed from the National Fetal Growth Studies data to the common alternative method that uses the average of the gestational ages (GAs) calculated for each fetal biometric measurement (biparietal diameter, head circumference, abdominal circumference, and femur length). METHODS: This retrospective cross-sectional study identified nonanomalous singleton pregnancies that had a crown-rump length plus at least 1 additional sonographic examination with complete fetal biometric measurements. With the use of the crown-rump length to establish the referent estimated date of delivery, each method's (National Institute of Child Health and Human Development regression versus Hadlock average [Radiology 1984; 152:497-501]), error at every examination was computed. Error, defined as the difference between the crown-rump length-derived GA and each method's predicted GA (weeks), was compared in 3 GA intervals: 1 (14 weeks-20 weeks 6 days), 2 (21 weeks-28 weeks 6 days), and 3 (≥29 weeks). In addition, the proportion of each method's examinations that had errors outside prespecified (±) day ranges was computed by using odds ratios. RESULTS: A total of 16,904 sonograms were identified. The overall and prespecified GA range subset mean errors were significantly smaller for the regression compared to the average (P < .01), and the regression had significantly lower odds of observing examinations outside the specified range of error in GA intervals 2 (odds ratio, 1.15; 95% confidence interval, 1.01-1.31) and 3 (odds ratio, 1.24; 95% confidence interval, 1.17-1.32) than the average method. CONCLUSIONS: In a contemporary unselected population of women dated by a crown-rump length-derived GA, the National Institute of Child Health and Human Development regression formula produced fewer estimates outside a prespecified margin of error than the commonly used Hadlock average; the differences were most pronounced for GA estimates at 29 weeks and later.

Disadvantages of a weight estimation formula for macrosomic fetuses: the Hart formula from a clinical perspective.

PURPOSE: Sonographic fetal weight (FW) estimation to detect macrosomic fetuses is an essential part of everyday routine work in obstetrics departments. Most of the commonly used weight estimation formulas underestimate FW when the actual birth weight (BW) exceeds 4000 g. One of the best-established weight estimation formulas is the Hadlock formula. In an effort to improve the detection rates of macrosomic infants, Hart et al. published a specially designed formula including maternal weight at booking. The usefulness of the Hart formula was tested. METHODS: Retrospective study of 3304 singleton pregnancies, birth weight ≥ 3500 g. The accuracy of the Hadlock and Hart formula were tested. A subgroup analysis examined the influence of the maternal weight. The Chi-squared test and one-way analysis of variation were carried out. For all analyses, p < 0.05 was considered statistically significant. RESULTS: The overall percentages of births falling within ± 5% and ± 10% of the BW using the Hadlock formula were 27% and 53%, respectively. Using the Hart formula, 24% and 54% were identified within these levels. With the Hart formula, 94% of all weight estimations fall within 4200 g ± 5% and nearly 100% fall within 4200 g ± 10%. CONCLUSIONS: Applying the Hart formula results in an overestimation of fetal weight in neonates with a birth weight < 4000 g and fails to identify high-risk fetuses. We, therefore, do not consider Hart's formula to be of clinical relevance.

Prediction of small-for-gestational-age neonate by third-trimester fetal biometry and impact of ultrasound-delivery interval.

OBJECTIVES: To compare third-trimester ultrasound screening methods to predict small-for-gestational age (SGA), and to evaluate the impact of the ultrasound-delivery interval on screening performance. METHODS: In this prospective study, data were collected from a multicenter singleton cohort study investigating the links between various exposures during pregnancy with birth outcome and later health in children. We included women, recruited in the first trimester, who had complete outcome data and had undergone third-trimester ultrasound examination. Demographic, clinical and biological variables were also collected from both parents. We compared prediction of delivery of a SGA neonate (birth weight < 10th percentile) by the following methods: abdominal circumference (AC) Z-score based on Hadlock curves (Hadlock AC), on INTERGROWTH-21st Project curves (Intergrowth AC) and on Salomon curves (Salomon AC); estimated fetal weight (EFW) Z-score based on Hadlock curves (Hadlock EFW) and on customized curves from Gardosi (Gardosi EFW); and fetal growth velocity based on change in AC between second and third trimesters (FGVAC). We also assessed the following ultrasound-delivery intervals: ≤ 4 weeks, ≤ 6 weeks and ≤ 10 weeks. RESULTS: Third-trimester ultrasound was performed in 1805 patients with complete outcome data, of whom 158 (8.8%) delivered a SGA neonate. Ultrasound examination was at a median gestational age of 32 (interquartile range, 31-33) weeks. The ultrasound-delivery interval was ≤ 4 weeks in 17.2% of cases, ≤ 6 weeks in 48.1% of cases and ≤ 10 weeks in 97.3% of cases. Areas under the receiver-operating characteristics curve (AUC) were 0.772 for Salomon AC, 0.768 for Hadlock EFW, 0.766 for Hadlock AC, 0.765 for Intergrowth AC, 0.708 for Gardosi EFW and 0.674 for FGVAC (all P < 0.0001). The screening method with the highest AUC for an ultrasound-delivery interval ≤ 4 weeks was Salomon AC (AUC, 0.856), ≤ 6 weeks was Hadlock AC (AUC, 0.824) and ≤ 10 weeks was Salomon AC (AUC, 0.780). At a fixed 10% false-positive rate, the best detection rates were 60.0%, 54.1% and 42.1% for intervals ≤ 4, ≤ 6 and ≤ 10 weeks, respectively. CONCLUSION: Third-trimester ultrasound measurements provide poor to moderate prediction of SGA. A shorter ultrasound-delivery interval provides better prediction than does a longer interval. Further studies are needed to test the effect of including maternal or biological characteristics in SGA screening. Copyright © 2016 ISUOG. Published by John Wiley & Sons Ltd.

Accuracy of sonographic fetal weight estimation prior to delivery in a Chinese han population.

OBJECTIVE: To compare the sonographic-estimated fetal weights (EFW) calculated with the Hadlock formula and with the Woo formula in a group of Chinese pregnant women. METHODS: We prospectively recruited term pregnancies for sonographic biometric examination. EFWs were calculated according to two formulas and compared with the corresponding birth weight (BW). We also assessed the sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of EFW for the diagnosis of small-for-gestational age (SGA) and large-for-gestational age (LGA) neonates. RESULTS: A total of 374 subjects who delivered within 7 days after the sonographic examinations was recruited. Using the Hadlock formula, the median absolute difference between EFW and BW was 182 g (15-308 g) and the median percentage difference was 5.3% (0.5-9.1%), whereas it was 230 g (62-367) and 7.1% (2.1-10.4%) for the Woo formula (p < 0.001). Several factors, namely the fetal presentation, gender, and high amniotic quantity, showed no evident impact on this predictive difference. Among the 175 women who delivered within 2 days after ultrasound, the sensitivity and specificity of Hadlock EFW were 100% and 97.1% for the detection of SGA and 48.1% and 97.3% for the detection of LGA, respectively. The PPV and NPV were 44.4% and 100.0% for the detection of SGA and 76.5% and 91.1% for the detection of LGA, respectively. CONCLUSIONS: EFWs calculated using the Hadlock formula for our research subjects were as accurate as those reported for other populations. The predictive performance showed a high NPV for the diagnosis of SGA and a relatively acceptable PPV for the diagnosis of LGA. © 2017 Wiley Periodicals, Inc. J Clin Ultrasound 45:465-471, 2017.

Development and external validation of Indian population-specific Garbhini-GA2 model for estimating gestational age in second and third trimesters.

Background: A large proportion of pregnant women in lower and middle-income countries (LMIC) seek their first antenatal care after 14 weeks of gestation. While the last menstrual period (LMP) is still the most prevalent method of determining gestational age (GA), ultrasound-based foetal biometry is considered more accurate in the second and third trimesters. In LMIC settings, the Hadlock formula, originally developed using data from a small Caucasian population, is widely used for estimating GA and foetal weight worldwide as the pre-programmed formula in ultrasound machines. This approach can lead to inaccuracies when estimating GA in a diverse population. Therefore, this study aimed to develop a population-specific model for estimating GA in the late trimesters that was as accurate as the GA estimation in the first trimester, using data from GARBH-Ini, a pregnancy cohort in a North Indian district hospital, and subsequently validate the model in an independent cohort in South India. Methods: Data obtained by longitudinal ultrasonography across all trimesters of pregnancy was used to develop and validate GA models for the second and third trimesters. The gold standard for GA estimation in the first trimester was determined using ultrasonography. The Garbhini-GA2, a polynomial regression model, was developed using the genetic algorithm-based method, showcasing the best performance among the models considered. This model incorporated three of the five routinely measured ultrasonographic parameters during the second and third trimesters. To assess its performance, the Garbhini-GA2 model was compared against the Hadlock and INTERGROWTH-21st models using both the TEST set (N = 1493) from the GARBH-Ini cohort and an independent VALIDATION dataset (N = 948) from the Christian Medical College (CMC), Vellore cohort. Evaluation metrics, including root-mean-squared error, bias, and preterm birth (PTB) rates, were utilised to comprehensively assess the model's accuracy and reliability. Findings: With first trimester GA dating as the baseline, Garbhini-GA2 reduced the GA estimation median error by more than three times compared to the Hadlock formula. Further, the PTB rate estimated using Garbhini-GA2 was more accurate when compared to the INTERGROWTH-21st and Hadlock formulae, which overestimated the rate by 22.47% and 58.91%, respectively. Interpretation: The Garbhini-GA2 is the first late-trimester GA estimation model to be developed and validated using Indian population data. Its higher accuracy in GA estimation, comparable to GA estimation in the first trimester and PTB classification, underscores the significance of deploying population-specific GA formulae to enhance antenatal care. Funding: The GARBH-Ini cohort study was funded by the Department of Biotechnology, Government of India (BT/PR9983/MED/97/194/2013). The ultrasound repository was partly supported by the Grand Challenges India-All Children Thriving Program, Biotechnology Industry Research Assistance Council, Department of Biotechnology, Government of India (BIRAC/GCI/0115/03/14-ACT). The research reported in this publication was made possible by a grant (BT/kiData0394/06/18) from the Grand Challenges India at Biotechnology Industry Research Assistance Council (BIRAC), an operating division jointly supported by DBT-BMGF-BIRAC. The external validation study at CMC Vellore was partly supported by a grant (BT/kiData0394/06/18) from the Grand Challenges India at Biotechnology Industry Research Assistance Council (BIRAC), an operating division jointly supported by DBT-BMGF-BIRAC and by Exploratory Research Grant (SB/20-21/0602/BT/RBCX/008481) from Robert Bosch Centre for Data Science and Artificial Intelligence (RBCDSAI), IIT Madras. An alum endowment from Prakash Arunachalam (BIO/18-19/304/ALUM/KARH) partly funded this study at the Centre for Integrative Biology and Systems Medicine, IIT Madras.