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.

Maternal rest improves growth in small-for-gestational-age fetuses (<10th percentile).

BACKGROUND: Optimal management of fetuses diagnosed as small for gestational age based on an estimated fetal weight of <10th percentile represents a major clinical problem. The standard approach is to increase fetal surveillance with serial biometry and antepartum testing to assess fetal well-being and timing of delivery. Observational studies have indicated that maternal rest in the left lateral position improves maternal cardiac output and uterine blood flow. However, maternal bed rest has not been recommended based on the results of a randomized clinical trial that showed that maternal rest does not improve fetal growth in small-for-gestational-age fetuses. This study was conducted to revisit this question. OBJECTIVE: This study aimed to determine whether maternal bed rest was associated with an increase in the fetal biometric parameters that reflect growth after the diagnosis of a small-for-gestational-age fetus. STUDY DESIGN: A retrospective study was conducted on fetuses who were diagnosed as small for gestational age because of an estimated fetal weight of <10th percentile for gestational age. The mothers were asked to rest in the left lateral recumbent position. Fetal biometry was performed 2 weeks after the diagnosis. All fetuses before entry into the study had a previous ultrasound that demonstrated an estimated fetal weight of >10th percentile. To assess the response to bed rest, the change in fetal biometric parameters (estimated fetal weight, head circumference, abdominal circumference, and femur length) after the recommendation of bed rest was computed for 2 periods: (1) before the diagnosis of a weight of <10th percentile vs at the time of diagnosis of a weight of <10th percentile and (2) at the time of diagnosis of a weight of <10th percentile vs 2 weeks after maternal bed rest. For repeated measures, proportions were compared using the McNemar test, and percentile values were compared using the Kruskal-Wallis test. A P value of <.05 was considered significant. To describe changes in the estimated fetal weight without bed rest, 2 control groups in which the mothers were not placed on bed rest after the diagnosis of a small-for-gestational-age fetus were included. RESULTS: A total of 265 fetuses were observed before and after maternal bed rest. The following were observed in this study: (1) after 2 weeks of maternal rest, 199 of 265 fetuses (75%) had a fetal weight of >10th percentile; (2) the median fetal weight percentile increased from 6.8 (interquartile range, 4.4-8.4) to 18.0 (interquartile range, 9.5-29.5) after 2 weeks of bed rest; (3) similar trends were noted for the head circumference, abdominal circumference, and femur length. In the groups of patients who were not asked to be on bed rest, a reassignment to a weight of >10th percentile at a follow-up examination only occurred in 7 of 37 patients (19%) in the Texas-Michigan group and 13 of 111 patients (12%) in the Colorado group compared with the bed rest group (199/265 [75%]) (P<.001). CONCLUSION: Patients who were prescribed 2 weeks of bed rest after the diagnosis of a fetal weight of <10th percentile had an increase in weight of >10th percentile in 199 of 265 fetuses (75%). This increase in fetal weight was significantly higher than that in the 2 control groups in which bed rest was not prescribed. This observation suggests that bed rest improves fetal growth in a subset of patients.

Multivariable prediction models for fetal macrosomia and large for gestational age: A systematic review.

BACKGROUND: The identification of large for gestational age (LGA) and macrosomic fetuses is essential for counselling and managing these pregnancies. OBJECTIVES: To systematically review the literature for multivariable prediction models for LGA and macrosomia, assessing the performance, quality and applicability of the included model in clinical practice. SEARCH STRATEGY: MEDLINE, EMBASE and Cochrane Library were searched until June 2022. SELECTION CRITERIA: We included observational and experimental studies reporting the development and/or validation of any multivariable prediction model for fetal macrosomia and/or LGA. We excluded studies that used a single variable or did not evaluate model performance. DATA COLLECTION AND ANALYSIS: Data were extracted using the Checklist for critical appraisal and data extraction for systematic reviews of prediction modelling studies checklist. The model performance measures discrimination, calibration and validation were extracted. The quality and completion of reporting within each study was assessed by its adherence to the TRIPOD (Transparent Reporting of a multivariable prediction model for Individual Prognosis Or Diagnosis) checklist. The risk of bias and applicability were measured using PROBAST (Prediction model Risk Of Bias Assessment Tool). MAIN RESULTS: A total of 8442 citations were identified, with 58 included in the analysis: 32/58 (55.2%) developed, 21/58 (36.2%) developed and internally validated and 2/58 (3.4%) developed and externally validated a model. Only three studies externally validated pre-existing models. Macrosomia and LGA were differentially defined by many studies. In total, 111 multivariable prediction models were developed using 112 different variables. Model discrimination was wide ranging area under the receiver operating characteristics curve (AUROC 0.56-0.96) and few studies reported calibration (11/58, 19.0%). Only 5/58 (8.6%) studies had a low risk of bias. CONCLUSIONS: There are currently no multivariable prediction models for macrosomia/LGA that are ready for clinical implementation.

Ultrasonic Estimation of Fetal Weight: Are Averaged Triplicate Measurements More Accurate Than Single Measurements?

OBJECTIVE: To assess whether, and to what extent, performing triplicate measurements can improve accuracy of estimation of fetal weight (EFW) compared to single measurements. METHODS: This was a prospective study conducted at a single medical center. A total of 100 term parturients with an anticipated delivery within 72 hours were recruited for EFW measurements. All examinations were done with adherence to the International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) guidelines. EFW was calculated using the Hadlock formula. Triplicate measurements from three different images were obtained for each parameter and the averaged values were used for clinical purposes. EFW calculated using average measurements was compared to EFW calculated using the first measurements. RESULTS: There was a small but significant improvement in EFW when using averaged measurements compared to single measurements (mean improvement 34 ± 105 g, P = .002). Deviance from birthweight in single measurements was significantly higher compared to averaged measurements (median deviance 198 versus 148 g, respectively, P = .005). This difference was more pronounced when assessing the 75th centile (348 versus 282 g, respectively). CONCLUSIONS: Using triplicate measurements instead of single measurements when performing EFW confers a small, but statistically significant, improvement to EFW accuracy. Using triplicate measurements for assessing EFW should be thus considered, especially in cases suspected of growth disorders.

A Novel Fetal Magnetic Resonance Imaging Lung Volume Nomogram Stratified by Estimated Fetal Weight.

INTRODUCTION: Fetal magnetic resonance imaging (MRI) lung volume nomograms are increasingly used to prognosticate neonatal outcomes in fetuses with suspected pulmonary hypoplasia. However, pregnancies complicated by fetal anomalies associated with pulmonary hypoplasia may also be complicated by fetal growth restriction (FGR). If a small lung volume is suspected in such cases, it is often unclear whether the lungs are "small" because of underlying lung pathology, or small fetal size. Existing MRI lung volume nomograms have mostly been stratified by gestational age (GA), rather than estimated fetal weight (EFW). Therefore, we aimed to develop a novel fetal lung volume nomogram stratified by EFW. METHODS: Consecutive fetal MRIs performed at a quaternary medical center from 2019 to 2021 were analyzed. MRIs performed due to fetal lung anomalies and cases with FGR were excluded. All MRIs were performed without IV contrast on GE 3 or 1.5 Tesla scanners (GE Healthcare). Images were reviewed by three experienced fetal radiologists. Freehand ROI in square centimeter was drawn around the contours of the lungs on consecutive slices from the apex to the base. The volume of the right, left and total lungs were calculated in mL. Lung volumes were plotted by both EFW and GA. RESULTS: Among 301 MRI studies performed during the study period, 170 cases met inclusion criteria and were analyzed. MRIs were performed between 19- and 38-week gestation, and a sonographic EFW was obtained within a mean of 2.9 days (SD ± 5.5 days, range 0-14 days) of each MRI. Nomograms stratified by both EFW and GA were created using 200 g. and weekly intervals respectively. A formula using EFW to predict total lung volume was calculated: LV = 0.07497804 EFW0.88276 (R2 = 0.87). CONCLUSIONS: We developed a novel fetal lung volume nomogram stratified by EFW. If validated, this nomogram may assist clinicians predict outcomes in cases of fetal pulmonary hypoplasia with concomitant FGR.

Fetal size vs growth: comparative analysis of 3 models of growth velocity based on third trimester estimated fetal weights for identifying stillbirth risk.

BACKGROUND: Fetal growth velocity is being recognized as an important parameter by which to monitor fetal wellbeing, in addition to assessment of fetal size. However, there are different models and standards in use by which velocity is being assessed. OBJECTIVE: We wanted to investigate 3 clinically applied methods of assessing growth velocity and their ability to identify stillbirth risk, in addition to that associated with small for gestational age. STUDY DESIGN: Retrospective analysis of prospectively recorded routine-care data of pregnancies with 2 or more third trimester scans in New Zealand. Results of the last 2 scans were used for the analysis. The models investigated to define slow growth were (1) 50+ centile drop between measurements, (2) 30+ centile drop, and (3) estimated fetal weight below a projected optimal weight range, based on predefined, scan interval specific cut-offs to define normal growth. Each method's ability to identify stillbirth risk was assessed against that associated with small-for-gestational age at last scan. RESULTS: The study cohort consisted of 71,576 pregnancies. The last 2 scans in each pregnancy were performed at an average of 32+1 and 35+6 weeks of gestation. The 3 models defined "slow growth" at the following differing rates: (1) 50-centile drop 0.9%, (2) 30-centile drop 5.1%, and (3) below projected optimal weight range 10.8%. Neither of the centile-based models identified at-risk cases that were not also small for gestational age at last scan. The projected weight range method identified an additional 79% of non-small-for-gestational-age cases as slow growth, and these were associated with a significantly increased stillbirth risk (relative risk, 2.0; 95% CI, 1.2-3.4). CONCLUSION: Centile-based methods fail to reflect adequacy of fetal weight gain at the extremes of the distribution. Guidelines endorsing such models might hinder the potential benefits of antenatal assessment of fetal growth velocity. A new, measurement-interval-specific projection model of expected fetal weight gain can identify fetuses that are not small for gestational age, yet at risk of stillbirth because of slow growth. The velocity between scans can be calculated using a freely available growth rate calculator (www.perinatal.org.uk/growthrate).

Accuracy of Dare's formula in estimating fetal birth weight in pregnant women.

OBJECTIVE: To evaluate the accuracy of Dare's formula in estimating fetal birth weight in pregnant women. METHODS: A prospective study was conducted at a tertiary care hospital in New Delhi after institutional ethical committee clearance. In all, 175 pregnant women with singleton pregnancies of 37 weeks or more were included. The aim was to assess fetal birth weight by Dare's formula and ultrasonography. This estimated fetal weight (EFW) was compared with actual birth weight (ABW) of newborn. RESULTS: Estimated fetal birth weight by Dare's formula was within 10% of ABW in 77 (44.00%) cases. Meanwhile in the majority (98; 56.00%), EFW by Dare's formula was not within 10% of ABW. The proportion of EFW by ultrasonography within 10% and not within 10% of ABW were comparable (50.29% [88] and 49.71% [87], respectively). CONCLUSION: Dare's formula can be used by medical personnel as a clinical method in routine prenatal care to estimate fetal weight, for better management of women in labor to decrease the maternal and neonatal mortality and morbidity.

Prenatal exposure to environmental phenols and fetal growth across pregnancy in the LIFECODES fetal growth study.

INTRODUCTION: Environmental phenols are endocrine disrupting chemicals hypothesized to affect early life development. Previous research examining the effects of phenols on fetal growth has focused primarily on associations with measures of size at delivery. Few have included ultrasound measures to examine growth across pregnancy. OBJECTIVE: Investigate associations between prenatal exposure to phenols and ultrasound and delivery measures of fetal growth. METHODS: Using the LIFECODES Fetal Growth Study (n = 900), a case-cohort including 248 small-for-gestational-age, 240 large-for-gestational age, and 412 appropriate-for-gestational-age births, we estimated prenatal exposure to 12 phenols using three urine samples collected during pregnancy (median 10, 24, and 35 weeks gestation). We abstracted ultrasound and delivery measures of fetal growth from medical records. We estimated associations between pregnancy-average phenol biomarker concentrations and repeated ultrasound measures of fetal growth using linear mixed effects models and associations with birthweight using linear regression models. We also used logistic regression models to estimate associations with having a small- or large-for-gestational birth. RESULTS: We observed positive associations between 2,4-dichlorophenol, benzophenone-3, and triclosan (TCS) and multiple ultrasound measures of fetal growth. For example, TCS was associated with a 0.09 (95 % CI: 0.01, 0.18) higher estimated fetal weight z-score longitudinally across pregnancy. This effect size corresponds to a 21 g increase in estimated fetal weight at 30 weeks gestation. Associations with delivery measures of growth were attenuated, but TCS remained positively associated with birthweight z-scores (mean difference: 0.13, 95 % CI: 0.02, 0.25). Conversely, methylparaben was associated with higher odds of a small-for-gestational age birth (odds ratio: 1.45, 95 % CI: 1.06, 1.98). DISCUSSION: We observed associations between some biomarkers of phenol exposure and ultrasound measures of fetal growth, though associations at the time of delivery were attenuated. These findings are consistent with hypotheses that phenols have the potential to affect growth during the prenatal period.

Association between risk of infant death and birth-weight z scores according to gestational age: A nationwide study using the Finnish Medical Birth Register.

OBJECTIVE: To investigate the association between infant mortality and birth weight using estimated fetal weight (EFW) versus birth-weight charts, by gestational age (GA). METHODS: This nationwide population-based study used data from the Finnish Medical Birth Register from 2006 to 2016 on non-malformed singleton live births at 24-41+6 weeks of gestation (N = 563 630). The outcome was death in the first year of life. Mortality risks by birth-weight z score, defined as a continuous variable using Marsál's EFW and Sankilampi's birth-weight charts, were assessed using generalized additive models by GA (24-27+6, 28-31+6, 32-36+6, 37-38+6, 39-41+6 weeks). We calculated z score thresholds associated with a two- and three-fold increased risk of infant death compared with newborns with a birth weight between 0 and 0.675 standard deviations. RESULTS: The z score thresholds (with corresponding centiles in parentheses) associated with a two-fold increase in infant mortality were: -3.43 (<0.1) at 24-27+6 weeks, -3.46 (<0.1) at 28-31+6 weeks, -1.29 (9.9) at 32-36+6 weeks, -1.18 (11.9) at 37-38+6 weeks, and - 1.34 (9.0) at 39-41+6 weeks according to the EFW chart. These values were - 2.43 (0.8), -2.62 (0.4), -1.34 (9.0), -1.37 (8.5), and - 1.43 (7.6) according to the birth-weight chart. CONCLUSION: The association between birth weight and infant mortality varies by GA whichever chart is used, suggesting that different thresholds for the screening of growth anomalies could be used across GA to identify high-risk newborns.

Indicated vs universal third-trimester ultrasound examination in low-risk pregnancies: a pre-post-intervention study.

BACKGROUND: In low-risk pregnancies, a third-trimester ultrasound examination is indicated if fundal height measurement and gestational age discrepancy are observed. Despite potential improvement in the detection of ultrasound abnormality, prior trials to date on universal third-trimester ultrasound examination in low-risk pregnancies, compared with indicated ultrasound examination, have not demonstrated improvement in neonatal or maternal adverse outcomes. OBJECTIVE: The primary objective was to determine if universal third-trimester ultrasound examination in low-risk pregnancies could attenuate composite neonatal adverse outcomes. The secondary objectives were to compare changes in composite maternal adverse outcomes and detection of abnormalities of fetal growth (fetal growth restriction or large for gestational age) or amniotic fluid (oligohydramnios or polyhydramnios). STUDY DESIGN: Our pre-post intervention study at 9 locations included low-risk pregnancies, those without indication for ultrasound examination in the third trimester. Compared with indicated ultrasound in the preimplementation period, in the postimplementation period, all patients were scheduled for ultrasound examination at 36.0-37.6 weeks. In both periods, clinicians intervened on the basis of abnormalities identified. Composite neonatal adverse outcomes included any of: Apgar score ≤5 at 5 minutes, cord pH <7.00, birth trauma (bone fracture or brachial plexus palsy), intubation for >24 hours, hypoxic-ischemic encephalopathy, seizure, sepsis (bacteremia proven with blood culture), meconium aspiration syndrome, intraventricular hemorrhage grade III or IV, periventricular leukomalacia, necrotizing enterocolitis, stillbirth after 36 weeks, or neonatal death within 28 days of birth. Composite maternal adverse outcomes included any of the following: chorioamnionitis, wound infection, estimated blood loss >1000 mL, blood transfusion, deep venous thrombus or pulmonary embolism, admission to intensive care unit, or death. Using Bayesian statistics, we calculated a sample size of 600 individuals in each arm to detect >75% probability of any reduction in primary outcome (80% power; 50% hypothesized risk reduction). RESULTS: During the preintervention phase, 747 individuals were identified during the initial ultrasound examination, and among them, 568 (76.0%) met the inclusion criteria at 36.0-37.6 weeks; during the postintervention period, the corresponding numbers were 770 and 661 (85.8%). The rate of identified abnormalities of fetal growth or amniotic fluid increased from between the pre-post intervention period (7.1% vs 22.2%; P<.0001; number needed to diagnose, 7; 95% confidence interval, 5-9). The primary outcome occurred in 15 of 568 (2.6%) individuals in the preintervention and 12 of 661 (1.8%) in the postintervention group (83% probability of risk reduction; posterior relative risk, 0.69 [95% credible interval, 0.34-1.42]). The composite maternal adverse outcomes occurred in 8.6% in the preintervention and 6.5% in the postintervention group (90% probability of risk; posterior relative risk, 0.74 [95% credible interval, 0.49-1.15]). The number needed to treat to reduce composite neonatal adverse outcomes was 121 (95% confidence interval, 40-200). In addition, the number to reduce composite maternal adverse outcomes was 46 (95% confidence interval, 19-74), whereas the number to prevent cesarean delivery was 18 (95% confidence interval, 9-31). CONCLUSION: Among low-risk pregnancies, compared with routine care with indicated ultrasound examination, implementation of a universal third-trimester ultrasound examination at 36.0-37.6 weeks attenuated composite neonatal and maternal adverse outcomes.

Agreement analysis between sonographic estimates and birth weight, by the WHO and intergrowth-21st tables, in newborns of diabetic mothers / Análise de concordância entre estimativas ultrassonográficas e peso ao nascer, pelas tabelas da OMS e Intergrowth-21st, em recém-nascidos de mães diabéticas

Abstract Objective To analyze the agreement, in relation to the 90th percentile, of ultrasound measurements of abdominal circumference (AC) and estimated fetal weight (EFW), between the World Health Organization (WHO) and the International Fetal and Newborn Growth Consortium for the 21st Century (intergrowth-21st) tables, as well as regarding birth weight in fetuses/newborns of diabetic mothers. Methods Retrospective study with data from medical records of 171 diabetic pregnant women, single pregnancies, followed between January 2017 and June 2018. Abdominal circumference and EFW data at admission (from 22 weeks) and predelivery (up to 3 weeks) were analyzed. These measures were classified in relation to the 90th percentile. The Kappa coefficient was used to analyze the agreement of these ultrasound variables between the WHO and intergrowth-21st tables, as well as, by reference table, these measurements and birth weight. Results The WHO study reported 21.6% large-for-gestational-age (LGA) newborns while the intergrowth-21st reported 32.2%. Both tables had strong concordances in the assessment of initial AC, final AC, and initial EFW (Kappa = 0.66, 0.72 and 0.63, respectively) and almost perfect concordance in relation to final EFW (Kappa = 0.91). Regarding birth weight, the best concordances were found for initial AC (WHO: Kappa = 0.35; intergrowth-21st: Kappa= 0.42) and with the final EFW (WHO: Kappa = 0.33; intergrowth- 21st: Kappa = 0.35). Conclusion The initial AC and final EFW were the parameters of best agreement regarding birth weight classification. The WHO and intergrowth-21st tables showed high agreement in the classification of ultrasound measurements in relation to the 90th

Resumo Objetivo Analisar a concordância, em relação ao percentil 90, das medidas ultrassonográficas da circunferência abdominal (CA) e peso fetal estimado (PFE), entre as tabelas da Organização Mundial de Saúde (OMS) e do International Fetal and Newborn Growth Consortium for the 21st Century integrowth-21st, bem como em relação ao peso ao nascer em fetos/recém-nascidos de mães diabéticas. Métodos Estudo retrospectivo com dados de prontuários de 171 gestantes diabéticas, com gestações únicas, seguidas entre Janeiro de 2017 e Junho de 2018. Foram analisados dados da CA e do PFE na admissão (a partir de 22 semanas) e no pré-parto (até 3 semanas). Essas medidas foram classificadas em relação ao percentil 90. O coeficiente Kappa foi utilizado para analisar a concordância entre as tabelas da OMS e Intergrowth-21st, assim como, por tabela de referência, entre as medidas e o peso ao nascer. Resultados O estudo da OMS relatou 21,6% dos recém nascidos grandes para a idade gestacional (GIG) enquanto que o estudo do intergrowth-21st relatou 32,2%. Ambas as tabelas tiveram fortes concordâncias na avaliação da CA inicial e final e PFE inicial (Kappa= 0,66, 0,72 e 0,63, respectivamente) e concordância quase perfeita em relação ao PFE final (Kappa= 0,91).Emrelação ao peso ao nascer, asmelhores concordâncias foram encontradas para aCAinicial (OMS: Kappa= 0,35; intergrowth-21st: Kappa= 0,42) e como PFE final (OMS: Kappa = 0,33; intergrowth-21st: Kappa= 0,35). Conclusão A CA inicial e o PFE final foram os parâmetros de melhor concordância em relação à classificação do peso ao nascer. As tabelas da OMS e intergrowth-21st mostraram alta concordância na classificação das medidas ultrassonográficas em relação ao percentil 90. Estudos são necessários para confirmar se alguma dessas tabelas é superior na previsão de resultados negativos a curto e longo prazo no grupo GIG.