Customized fetal growth standard compared with the INTERGROWTH-21st century standard at predicting small-for-gestational-age neonates

Perinatal Outcomes Based on Placental Cord Insertion Site

Presently, societal guidelines differ regarding evaluation and management of variations in placental cord insertion (PCI). This variation may in part be secondary to inconsistency in reported risk associated with marginal and velamentous cord insertion (VCI). The objective of this study is to compare perinatal outcomes based on PCI site in pregnancies at risks for fetal growth disorders.This was a secondary analysis of singletons with growth assessment between 26 and 36 weeks of gestation. Fetuses with chromosomal or congenital malformations were excluded. The primary outcomes studied were neonatal small for gestational age (SGA), birthweight, and gestational age (GA) at delivery. Other outcomes included a composite of adverse neonatal outcomes, a composite score of obstetrical outcomes, and hypoglycemia. Categorical data were analyzed with χ2 and continuous data with Kruskal-Wallis tests. Pairwise comparisons and Bonferroni corrections were utilized. Logistic regression model was applied to assess the association of hypoglycemia with VCI.Of the 1,054 fetuses, 660 had confirmed PCI site by pathology review. Of those, 609 (92%) had central cord insertion, 37 (5.6%) had marginal, and 14 (2.1%) had velamentous. There was no difference in SGA or preterm birth. Those with a VCI had lower GA at delivery than placentas with central cord insertion (37.6 vs. 38.6, p = 0.032) and higher rates of hypoglycemia than those with other types of PCIs, 26.2% for central cord insertion, 20% for marginal cord insertion, and 71.4% for VCI (p < 0.001). After controlling for confounders, VCI remained significantly associated with hypoglycemia (adjusted odds ratio = 5.52; 95% confidence interval: 1.54-19.82).VCI was associated with lower GA at delivery and higher rates of neonatal hypoglycemia compared with other PCIs. Additional studies are needed to assess the association of marginal cord insertion and VCI and adverse perinatal outcomes. · VCI was associated with neonatal hypoglycemia.. · VCI is associated with earlier gestational age at delivery.. · The rate of VCI is 2.1% in this cohort..

Comparison of umbilical artery pulsatility index reference ranges

OBJECTIVE

To compare the accuracy of four published reference standards for the umbilical artery pulsatility index (UA-PI) in predicting small-for-gestational age (SGA), adverse neonatal outcomes and obstetric complications in pregnancies at risk for fetal growth restriction.

METHODS

This was a secondary analysis of a prospective study of singleton pregnancies that underwent fetal growth assessment by ultrasound between 26 and 36 weeks' gestation. Pregnancies with estimated fetal weight or abdominal circumference < 20th percentile with UA-PI measurements available were included. We excluded fetuses with chromosomal anomaly or congenital malformation and those without delivery information. The predictive ability of UA-PI > 95th percentile according to the reference standards of Acharya et al., the INTERGROWTH-21st Project, the Fetal Medicine Foundation and Parra-Cordero et al. for SGA, a composite of adverse neonatal outcomes and a composite of obstetric complications was compared using the area under the receiver-operating-characteristics curve (AUC). Sensitivity, specificity and positive and negative predictive values were calculated.

RESULTS

Of the 1054 pregnancies that underwent fetal growth evaluation by ultrasound, 207 were included in our analysis. SGA, adverse neonatal outcomes and obstetric complications were diagnosed in 94 (45.4%), 50 (24.2%) and 69 (33.3%) cases, respectively. All reference standards had similar and statistically significant but poor predictive accuracy for SGA (AUC of 0.55 to 0.56), adverse neonatal outcomes (AUC of 0.57 to 0.60) and obstetric complications (AUC of 0.55 for all).

CONCLUSIONS

The reference standards for UA-PI evaluated herein have poor predictive ability for SGA, adverse neonatal outcomes and obstetric complications. At present, no particular UA-PI reference standard can be recommended over others. Larger trials are needed to answer this research question. © 2024 International Society of Ultrasound in Obstetrics and Gynecology.

Comparing population-based fetal growth standards in a US cohort

BACKGROUND

No fetal growth standard is currently endorsed for universal use in the United States. Newer standards improve upon the methodologic limitations of older studies; however, before adopting into practice, it is important to know how recent standards perform at identifying fetal undergrowth or overgrowth and at predicting subsequent neonatal morbidity or mortality in US populations.

OBJECTIVE

To compare classification of estimated fetal weight that is <5th or 10th percentile or >90th percentile by 6 population-based fetal growth standards and the ability of these standards to predict a composite of neonatal morbidity and mortality.

STUDY DESIGN

We used data from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-be cohort, which recruited nulliparous women in the first trimester at 8 US clinical centers (2010-2014). Estimated fetal weight was obtained from ultrasounds at 16 to 21 and 22 to 29 weeks of gestation (N=9534 women). We calculated rates of fetal growth restriction (estimated fetal weight <5th and 10th percentiles; fetal growth restriction<5 and fetal growth restriction<10) and estimated fetal weight >90th percentile (estimated fetal weight>90) from 3 large prospective fetal growth cohorts with similar rigorous methodologies: INTERGROWTH-21, World Health Organization-sex-specific and combined, Eunice Kennedy Shriver National Institute of Child Health and Human Development race-ethnic-specific and unified, and the historic Hadlock reference. To determine whether differential classification of fetal growth restriction or estimated fetal weight >90 among standards was clinically meaningful, we then compared area under the curve and sensitivity of each standard to predict small for gestational age or large for gestational age at birth, composite perinatal morbidity and mortality alone, and small for gestational age or large for gestational age with composite perinatal morbidity and mortality.

RESULTS

The standards classified different proportions of fetal growth restriction and estimated fetal weight>90 for ultrasounds at 16 to 21 (visit 2) and 22 to 29 (visit 3) weeks of gestation. At visit 2, the Eunice Kennedy Shriver National Institute of Child Health and Human Development race-ethnic-specific, World Health Organization sex-specific and World Health Organization-combined identified similar rates of fetal growth restriction<10 (8.4%-8.5%) with the other 2 having lower rates, whereas Eunice Kennedy Shriver National Institute of Child Health and Human Development race-ethnic-specific identified the highest rate of fetal growth restriction<5 (5.0%) compared with the other references. At visit 3, World Health Organization sex-specific classified 9.2% of fetuses as fetal growth restriction<10, whereas the other 5 classified a lower proportion as follows: World Health Organization-combined (8.4%), Eunice Kennedy Shriver National Institute of Child Health and Human Development race-ethnic-specific (7.7%), INTERGROWTH (6.2%), Hadlock (6.1%), and Eunice Kennedy Shriver National Institute of Child Health and Human Development unified (5.1%). INTERGROWTH classified the highest (21.3%) as estimated fetal weight>90 whereas Hadlock classified the lowest (8.3%). When predicting composite perinatal morbidity and mortality in the setting of early-onset fetal growth restriction, World Health Organization had the highest area under the curve of 0.53 (95% confidence interval, 0.51-0.53) for fetal growth restriction<10 at 22 to 29 weeks of gestation, but the areas under the curve were similar among standards (0.52). Sensitivity was generally low across standards (22.7%-29.1%). When predicting small for gestational age birthweight with composite neonatal morbidity or mortality, for fetal growth restriction<10 at 22 to 29 weeks of gestation, World Health Organization sex-specific had the highest area under the curve (0.64; 95% confidence interval, 0.60-0.67) and INTERGROWTH had the lowest (area under the curve=0.58; 95% confidence interval 0.55-0.62), though all standards had low sensitivity (7.0%-9.6%).

CONCLUSION

Despite classifying different proportions of fetuses as fetal growth restriction or estimated fetal weight>90, all standards performed similarly in predicting perinatal morbidity and mortality. Classification of different percentages of fetuses as fetal growth restriction or estimated fetal weight>90 among references may have clinical implications in the management of pregnancies, such as increased antenatal monitoring for fetal growth restriction or cesarean delivery for suspected large for gestational age. Our findings highlight the importance of knowing how standards perform in local populations, but more research is needed to determine if any standard performs better at identifying the risk of morbidity or mortality.

Predictive ability of fetal growth charts in identifying kindergarten-age developmental challenges: a cohort study

BACKGROUND

The Society for Maternal-Fetal Medicine recommends defining fetal growth restriction as an estimated fetal weight or abdominal circumference <10th percentile of a population-based reference. However, because multiple references are available, an understanding of their ability to identify infants at increased risk due to fetal growth restriction is critical. Previous studies have focused on the ability of different population references to identify short-term outcomes, but fetal growth restriction also has longer-term consequences for child development.

OBJECTIVE

This study aimed to estimate the association between estimated fetal weight percentiles on the INTERGROWTH-21st and World Health Organization fetal growth charts and kindergarten-age childhood development, and establish the charts' discriminatory ability in predicting kindergarten-age developmental challenges.

STUDY DESIGN

We conducted a retrospective cohort study linking obstetrical ultrasound scans conducted at BC Women's Hospital, Vancouver, Canada, with population-based standardized kindergarten test results. The cohort was limited to nonanomalous, singleton fetuses scanned at ≥28 weeks' gestation from 2000 to 2011, with follow-up until 2017. We classified estimated fetal weight into percentiles using the INTERGROWTH-21st and World Health Organization charts. We used generalized additive modeling to link estimated fetal weight percentile with routine province-wide kindergarten readiness test results. We calculated the area under the receiver-operating characteristic curve and other measures of diagnostic accuracy with 95% confidence intervals at select percentile cut-points of the charts. We repeated analyses using the Hadlock chart to help contextualize findings. The main outcome measure was the total Early Development Instrument score (/50). Secondary outcomes were Early Development Instrument subdomain scores for language and cognitive development, and for communication skills and general knowledge, as well as designation of "developmentally vulnerable" or "special needs".

RESULTS

Among 3418 eligible fetuses, those with lower estimated fetal weight percentiles had systematically lower Early Development Instrument scores and increased risks of developmental vulnerability. However, the clinical significance of differences was modest in magnitude (eg, total Early Development Instrument score -2.8 [95% confidence interval, -5.1 to -0.5] in children with an estimated fetal weight in 3rd-9th percentile of INTERGROWTH-21st chart [vs reference of 31st-90th]). The charts' predictive abilities for adverse child development were limited (eg, area under the receiver-operating characteristic curve <0.53 for all 3 charts).

CONCLUSION

Lower estimated fetal weight percentiles on the INTERGROWTH-21st and World Health Organization charts indicate increased risks of adverse kindergarten-age child development at the population level, but are not accurate individual-level predictors of adverse child development.

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.

Risk of adverse perinatal outcomes in pregnancies with "small" fetuses not meeting Delphi consensus criteria for fetal growth restriction

BACKGROUND

Previous research endeavors examining the association between clinical characteristics, sonographic indices, and the risk of adverse perinatal outcomes in pregnancies complicated by fetal growth restriction have been hampered by a lack of agreement regarding its definition. In 2016, a consensus definition was reached by an international panel of experts via the Delphi procedure, but as it currently stands, this has not been endorsed by all professional organizations.

OBJECTIVE

This study aimed to assess whether an independent association exists between estimated fetal weight and/or abdominal circumference of <10th percentile and adverse perinatal outcomes when consensus criteria for growth restriction are not met.

STUDY DESIGN

Data were derived from a passive prospective cohort of singleton nonanomalous pregnancies at a single academic tertiary care institution (2010-2022) that fell into 3 groups: (1) consecutive fetuses that met the Delphi criteria for fetal growth restriction, (2) small-for-gestational-age fetuses that failed to meet the consensus criteria, and (3) fetuses with birthweights of 20th to 80th percentile randomly selected as an appropriately grown (appropriate-for-gestational-age) comparator group. This nested case-control study used 1:1 propensity score matching to adjust for confounders among the 3 groups: fetal growth restriction cases, small-for-gestational-age cases, and controls. Our primary outcome was a composite: perinatal demise, 5-minute Apgar score of <7, cord pH of ≤7.10, or base excess of ≥12. Pregnancy characteristics with a P value of <.2 on univariate analyses were considered for incorporation into a multivariable model along with fetal growth restriction and small-for-gestational-age to evaluate which outcomes were independently predictive of adverse perinatal outcomes.

RESULTS

Overall, 2866 pregnancies met the inclusion criteria. After propensity score matching, there were 2186 matched pairs, including 511 (23%), 1093 (50%), and 582 (27%) patients in the small-for-gestational-age, appropriate-for-gestational-age, and fetal growth restriction groups, respectively. Moreover, 210 pregnancies (10%) were complicated by adverse perinatal outcomes. None of the pregnancies with small-for-gestational-age OR appropriate-for-gestational-age fetuses resulted in perinatal demise. Twenty-three of 511 patients (5%) in the small-for-gestational-age group had adverse outcomes based on 5-minute Apgar scores and/or cord gas results compared with 77 of 1093 patients (7%) in the appropriate-for-gestational-age group (odds ratio, 0.62; 95% confidence interval, 0.39-1.00). Furthermore, 110 of 582 patients (19%) with fetal growth restriction that met the consensus criteria had adverse outcomes (odds ratio, 3.08; 95% confidence interval, 2.25-4.20), including 34 patients with perinatal demise or death before discharge. Factors independently associated with increased odds of adverse outcomes included chronic hypertension, hypertensive disorders of pregnancy, and early-onset fetal growth restriction. Small-for-gestational age was not associated with the primary outcome after adjustment for 6 other factors included in a model predicting adverse perinatal outcomes. The bias-corrected bootstrapped area under the receiver operating characteristic curve for the model was 0.72 (95% confidence interval, 0.66-0.74). The bias-corrected bootstrapped area under the receiver operating characteristic curve for a 7-factor model predicting adverse perinatal outcomes was 0.72 (95% confidence interval, 0.66-0.74).

CONCLUSION

This study found no evidence that fetuses with an estimated fetal weight and/or abdominal circumference of 3rd to 9th percentile that fail to meet the consensus criteria for fetal growth restriction (based on Doppler waveforms and/or growth velocity of ≥32 weeks) are at increased risk of adverse outcomes. Although the growth of these fetuses should be monitored closely to rule out evolving growth restriction, most cases are healthy constitutionally small fetuses. The management of these fetuses in the same manner as those with suspected pathologic growth restriction may result in unnecessary antenatal testing and increase the risk of iatrogenic complications resulting from preterm or early term delivery of small fetuses that are at relatively low risk of adverse perinatal outcomes.

Reference Values for Birth Weight in Relation to Gestational Age in Poland and Comparison with the Global Percentile Standards

INTRODUCTION

Percentiles of birth weight by gestational age (GA) are an essential tool for clinical assessment and initiating interventions to reduce health risks. Unfortunately, Poland lacks a reference chart for assessing newborn growth based on the national population. This study aimed to establish a national reference range for birth weight percentiles among newborns from singleton deliveries in Poland. Additionally, we sought to compare these percentile charts with the currently used international standards, INTERGROWTH-21 and WHO.

MATERIALS AND METHODS

All singleton live births (n = 3,745,239) reported in Poland between 2010 and 2019 were analyzed. Using the Lambda Mu Sigma (LMS) method, the Generalized Additive Models for Location Scale, and Shape (GAMLSS) package, smoothed percentile charts (3-97) covering GA from 23 to 42 weeks were constructed.

RESULTS

The mean birth weight of boys was 3453 ± 540 g, and this was higher compared with that of girls (3317 ± 509 g). At each gestational age, boys exhibited higher birth weights than girls. The weight range between the 10th and 90th percentiles was 1061 g for boys and 1016 g for girls. Notably, the birth weight of Polish newborns was higher compared to previously published international growth standards.

CONCLUSION

The reference values for birth weight percentiles established in this study for Polish newborns differ from the global standards and are therefore useful for evaluating the growth of newborns within the national population. These findings hold clinical importance in identifying neonates requiring postbirth monitoring.

[Ante- and postnatal growth charts in France - guidelines for clinical practice from the Collège national des gynécologues et obstétriciens français (CNGOF) and from the Société française de néonatologie (SFN)]

OBJECTIVE

To recommend the most appropriate biometric charts for the detection of antenatal growth abnormalities and postnatal growth surveillance.

METHODS

Elaboration of specific questions and selection of experts by the organizing committee to answer these questions; analysis of the literature by experts and drafting conclusions by assigning a recommendation (strong or weak) and a quality of evidence (high, moderate, low, very low) and for each question; all these recommendations have been subject to multidisciplinary external review (obstetrician gynecologists, pediatricians). The objective for the reviewers was to verify the completeness of the literature review, to verify the levels of evidence established and the consistency and applicability of the resulting recommendations. The overall review of the literature, quality of evidence and recommendations were revised to take into consideration comments from external reviewers.

RESULTS

Antenatally, it is recommended to use all WHO fetal growth charts for EFW and common ultrasound biometric measurements (strong recommendation; low quality of evidence). Indeed, in comparison with other prescriptive curves and descriptive curves, the WHO prescriptive charts show better performance for the screening of SGA (Small for Gestational Age) and LGA (Large for Gestational Age) with adequate proportions of fetuses screened at extreme percentiles in the French population. It also has the advantages of having EFW charts by sex and biometric parameters obtained from the same perspective cohort of women screened by qualified sonographers who measured the biometric parameters according to international standards. Postnatally, it is recommended to use the updated Fenton charts for the assessment of birth measurements and for growth monitoring in preterm infants (strong recommendation; moderate quality of evidence) and for the assessment of birth measurements in term newborn (expert opinion).

CONCLUSION

It is recommended to use WHO fetal growth charts for antenatal growth monitoring and Fenton charts for the newborn.

Perinatal and Neonatal Outcomes in Fetal Growth Restriction and Small for Gestational Age

Alterations in intrauterine fetal growth increase the risk of adverse perinatal and neonatal outcomes. In this retrospective study, we analyzed data of 906 pregnancies collected in our maternal fetal medicine center, with different patterns of growth: 655 AGA (Appropriate for Gestational Age), 62 SGA (Small for Gestational Age: fetuses born with a weight less than 10° centile, not diagnosed before delivery), 189 FGR (Fetal Growth Restriction, classified in early and late according to gestational week at diagnosis). For each group, we compared maternal characteristics, gestational age at delivery, and perinatal and neonatal outcomes. Risk factors for fetal growth alterations were advanced age, being primiparous, and a lower pregestational BMI. FGR fetuses were born at earlier gestational ages (32 [IQR 29-38] early-FGR and 38 [IQR 36-39] late-FGR), with blood gas values comparable to the AGA group but worse neonatal outcomes related to prematurity. Unexpected SGA fetuses born by vaginal delivery, managed as AGA, were more hyperlactacidemic (4.4 [IQR 2.7-5.5]) and hypoxemic (-5.0 [IQR -7.1-2.8]) at birth than both AGA and FGR. However, neonatal outcomes (accesses and days of hospitalization in NICU) were better than FGR, likely due to gestational age and birthweight similar to AGA.

Testing the assumptions of customized intrauterine growth charts using national birth studies

INTRODUCTION

Customized intrauterine growth charts are widely used for growth monitoring and research. They are based on three assumptions: (1) estimated fetal weight (EFW) has a normal distribution with a constant coefficient of variation at all gestational ages; (2) Hadlock's growth curve accurately describes the relation between EFW and gestational ages; (3) associations between EFW and the fetal and maternal characteristics included in the customization model (fetal sex, pre-pregnancy weight, height, parity) are proportional throughout pregnancy. The aim of this study was to test whether these underlying assumptions are verified.

MATERIAL AND METHODS

Data came from (1) the French Longitudinal Study of Children (ELFE) cohort, which recruited births after 32 weeks' gestation in 349 maternity hospitals in France in 2011, and (2) the National Perinatal Survey, which included births from all French maternity hospitals in 2016. The study population included, respectively, 6 920 and 8 969 singleton non-malformed term live births with data on customization characteristics and EFW. We computed the coefficient of variation by gestational age and then modeled the association of gestational age, maternal and fetal characteristics with EFW at the second and third trimester ultrasound and with birthweight using linear regression. To assess the proportionality of the impact of maternal and fetal characteristics, we computed the percent change in weight associated with these characteristics at these three time points.

RESULTS

The coefficient of variation was close to 12% at each gestational age, but EFW was not normally distributed, leading to small but systematic underestimation of fetuses under the 10th percentile. Weights representing the 50th and 10th percentiles based on Hadlock's growth trajectory were lower than observed or predicted weights. Most characteristics more strongly impacted weight at birth than during pregnancy. In the French Longitudinal study of Children (ELFE) cohort, boys were 1.8% (95% confidence interval [CI] 1.3-2.4) heavier than girls in the third trimester, whereas this percentage was 4.6% (95% CI 4.0-5.2) at birth. In the National Perinatal Survey, these percentages were 2.3% (95% CI 1.8-2.8) and 4.3% (95% CI 3.8-4.8).

CONCLUSIONS

These results from two independent sources revealed discrepancies between routine clinical EFW data used for growth monitoring and the customized growth model's assumptions.

Which chart and which cut-point: deciding on the INTERGROWTH, World Health Organization, or Hadlock fetal growth chart

OBJECTIVE

To determine how various centile cut points on the INTERGROWTH-21st (INTERGROWTH), World Health Organization (WHO), and Hadlock fetal growth charts predict perinatal morbidity/mortality, and how this relates to choosing a fetal growth chart for clinical use.

METHODS

We linked antenatal ultrasound measurements for fetuses > 28 weeks' gestation from the British Columbia Women's hospital ultrasound unit with the provincial perinatal database. We estimated the risk of perinatal morbidity/mortality (decreased cord pH, neonatal seizures, hypoglycemia, and perinatal death) associated with select centiles on each fetal growth chart (the 3rd, 10th, the centile identifying 10% of the population, and the optimal cut-point by Youden's Index), and determined how well each centile predicted perinatal morbidity/mortality.

RESULTS

Among 10,366 pregnancies, the 10th centile cut-point had a sensitivity of 11% (95% CI 8, 14), 13% (95% CI 10, 16), and 12% (95% CI 10, 16), to detect fetuses with perinatal morbidity/mortality on the INTERGROWTH, WHO, and Hadlock charts, respectively. All charts performed similarly in predicting perinatal morbidity/mortality (area under the curve [AUC] =0.54 for all three charts). The statistically optimal cut-points were the 39th, 31st, and 32nd centiles on the INTERGROWTH, WHO, and Hadlock charts respectively.

CONCLUSION

The INTERGROWTH, WHO, and Hadlock fetal growth charts performed similarly in predicting perinatal morbidity/mortality, even when evaluating multiple cut points. Deciding which cut-point and chart to use may be guided by other considerations such as impact on workflow and how the chart was derived.

Impact of Using Abdominal Circumference Independently in the Diagnosis of Fetal Growth Restriction

OBJECTIVE

Society for Maternal-Fetal Medicine guidelines for diagnosing fetal growth restriction (FGR) have broadened the definition to include abdominal circumference (AC) <10^th percentile for gestational age (GA) regardless of estimated fetal weight (EFW). We aimed to compare the ability of three definitions of FGR to predict small for gestational age (SGA) neonates and adverse outcomes.

METHODS

We performed a secondary analysis of a prospective cohort of patients who underwent assessment of fetal growth between GA of 26 and 36 weeks. We compared three definitions of FGR: EFW <10^th percentile; AC <10^th percentile; either EFW or AC <10^th percentile. The primary outcome was successful prediction of neonatal SGA. Secondary outcomes included a composite adverse neonatal outcome (CANO). We further compared these definitions of FGR using area under receiver operative curves (AUC) to measure their discriminatory abilities.

RESULTS

About 1054 women met inclusion criteria. Ninety-one (8.6%) had EFW <10^th percentile, 122 (11.6%) had AC <10^th percentile, and 137 (12.9%) had either EFW or AC <10^th percentile. SGA was seen in 139 (13.2%); CANO was seen in 139 (13.2%). Ability for detecting neonatal SGA was significantly better when the definition included both EFW or AC <10^th percentile compared to either variable independently. The AUC were: 0.74, 0.73, 0.69; P = .0003. There was no statistical significance in ability for predicting CANO (AUC 0.51, 0.51, 0.50; P = .7447).

CONCLUSIONS

Addition of AC as a criterion for diagnosing FGR improves our ability to predict neonatal SGA compared to using EFW alone. All three definitions were poorly predictive of neonates at risk for adverse outcomes.

Customized GROW vs INTERGROWTH-21st birthweight standards to identify small for gestational age associated perinatal outcomes at term

BACKGROUND

Fetal growth restriction is associated with stillbirth and other adverse pregnancy outcomes, and use of the correct weight standard is an essential proxy indicator of growth status and perinatal risk.

OBJECTIVE

We sought to assess the performance of two international birthweight standards for their ability to identify perinatal morbidity and mortality indicators associated with small for gestational age (SGA) infants at term.

STUDY DESIGN

This retrospective cohort study used data from a multi-center perinatal quality initiative including a multi-ethnic dataset of 125,826 births from 2012-2017. Of the singleton term births, 92,622 had complete outcome data including stillbirth, neonatal death, 5-minute Apgar <7, neonatal glucose instability and need for newborn transfer to a higher level of care or NICU admission. The customized (GROW) and INTERGROWTH-21^st (IG21) birthweight standards were applied to determine SGA (<10^th centile) according to their respective methods and formulae. Associations with adverse outcomes were expressed as relative risk (RR) with 95% confidence interval (CI) and population attributable fraction (PAF).

RESULTS

GROW classified 9,578 (10.3%) and IG21 classified 4,079 (4.4%) pregnancies as SGA, respectively. For all of the outcomes assessed, GROW identified more SGA infants with adverse outcomes than IG21, including more stillbirths, perinatal deaths, low Apgar scores, glucose instability, newborn seizure and transfers to a higher level of care. Thirteen of the 27 stillbirths (48%) that were SGA by either method were identified as SGA by GROW but not by IG21. Similarly, additional cases of all other adverse outcome indicators were identified by GROW as SGA, while only in one category (glucose instability) did IG21 identify 9 of 295 cases (3.1%) which were not identified as SGA by GROW.

CONCLUSION

Customized assessment using GROW results in increased identification of small for gestational age term babies that are at significantly increased risk of an array of adverse pregnancy outcomes.

Prediction of Late-Onset Small for Gestational Age and Fetal Growth Restriction by Fetal Biometry at 35 Weeks and Impact of Ultrasound-Delivery Interval: Comparison of Six Fetal Growth Standards

Small-for-gestational-age (SGA) infants have been associated with increased risk of adverse perinatal outcomes (APOs). In this work, we assess the predictive ability of the ultrasound-estimated percentile weight (EPW) at 35 weeks of gestational age to predict late-onset SGA and APOs, according to six growth standards, and whether the ultrasound–delivery interval influences the detection rate. To this purpose, we analyze a retrospective cohort study of 9585 singleton pregnancies. EPWs at 35 weeks were calculated to the customized Miguel Servet University Hospital (MSUH) and Figueras standards and the non-customized MSUH, Fetal Medicine Foundation (FMF), INTERGROWTH-21st, and WHO standards. As results of our analysis, for a 10% false positive rate, the detection rates for SGA ranged between 48.9% with the customized Figueras standard (AUC 0.82) and 60.8% with the non-customized FMF standard (AUC 0.87). Detection rates to predict SGA by ultrasound–delivery interval (1–6 weeks) show higher detection rates as intervals decrease. APOs detection rates ranged from 27.0% with FMF to 7.9% with the Figueras standard. In conclusion, the ability of EPW to predict SGA at 35 weeks is good for all standards, and slightly better for non-customized standards. The APO detection rate is significantly greater for non-customized standards.

Prediction of Large-for-Gestational-Age Neonates by Different Growth Standards

OBJECTIVE

Compare the accuracy of the Hadlock, the NICHD, and the Fetal Medicine Foundation (FMF) charts to detect large-for-gestational-age (LGA) and adverse neonatal outcomes (as a secondary outcome).

METHODS

This is a secondary analysis from a prospective study that included singleton non-anomalous gestations with growth ultrasound at 26-36 weeks. LGA was suspected with estimated fetal weight > 90^th percentile by the NICHD, FMF, and Hadlock charts. LGA was diagnosed with birth weight > 90^th percentile. We tested the performance of these charts to detect LGA and adverse neonatal outcomes (neonatal intensive care unit admission, Ph < 7.1, Apgar <7 at 5 minutes, seizures, and neonatal death) by calculating the area under the curve, sensitivity, specificity, positive predictive value, and negative predictive value.

RESULTS

Of 1054 pregnancies, 123 neonates (12%) developed LGA. LGA was suspected in 58 (5.5%) by Hadlock, 229 (21.7%) by NICHD standard, and 231 (22%) by FMF chart. The NICHD standard (AUC: .79; 95% CI: .75-.83 vs. AUC .64; 95%CI: .6-.68; p = < .001) and FMF chart (AUC: .81 95% CI: .77-.85 vs. AUC .64; 95%CI: .6-.68; p = < .001) were more accurate than Hadlock. The FMF and NICHD had higher sensitivity (77.2 vs. 72.4 vs. 30.1%) but Hadlock had higher specificity for LGA (97.5 vs. 88.5 vs. 85.4%). All standards were poor predictors for adverse neonatal outcomes.

CONCLUSIONS

The NICHD and the FMF standards may increase the detection rate of LGA in comparison to the Hadlock chart. However, this may increase obstetrical interventions.

Obstetric and pediatric growth charts for the detection of late-onset fetal growth restriction and neonatal adverse outcomes

OBJECTIVES

Late-onset fetal growth restriction (FGR) has heterogeneous prenatal and postnatal diagnostic criteria. We compared the prenatal and postnatal diagnosis of late-onset FGR and their ability to predict adverse perinatal outcomes.

METHODS

Retrospective cohort study of 5442 consecutive singleton pregnancies that delivered beyond 34 + 0 weeks. Prenatal diagnosis of FGR was based on customized fetal growth standards and fetal Doppler while postnatal diagnosis was based on a birthweight <3rd percentile according to newborn charts (Olsen's charts and Intergrowth 21st century programme). Perinatal outcomes were analyzed depending on whether the diagnosis was prenatal, postnatal or both.

RESULTS

A total of 94 out of 5442 (1.7%) were diagnosed as late-onset FGR prenatally. Olsen's chart and Intergrowth 21st chart detected that 125/5442 (2.3%) and 106/5442 (2.0%) of infants had a birthweight <3rd percentile, respectively. These charts identified 35/94 (37.2%) and 40/94 (42.6%) of the newborns with a prenatal diagnosis of late-onset FGR. Prenatally diagnosed late-onset FGR infants were at a higher risk for hypoglycemia, jaundice and polycythemia. Both prenatally and postnatally diagnosed as late-onset FGR had a higher risk for respiratory distress syndrome when compared to non-FGR. The higher risks for intensive care admission and composite adverse outcomes were observed in those with a prenatal diagnosis of late-onset FGR that was confirmed after birth.

CONCLUSIONS

Current definitions of pre- and postnatal late-onset FGR do not match in more than half of cases. Infants with a prenatal or postnatal diagnosis of this condition have an increased risk of neonatal morbidity even if these diagnoses are not coincident.

Should Fetal Growth Charts Be References or Standards?

BACKGROUND

Fetal growth standards (prescriptive charts derived from low-risk pregnancies) are theoretically better tools to monitor fetal growth than conventional references. We examined how modifying chart inclusion criteria influenced the resulting curves.

METHODS

We summarized estimated fetal weight (EFW) distributions from a hospital's routine 32-week ultrasound in all nonanomalous singleton fetuses (reference) and in those without maternal-fetal conditions affecting fetal growth (standard). We calculated EFWs for the 3rd, 5th, 10th, and 50th percentiles, and the proportion of fetuses each chart classified as small for gestational age.

RESULTS

Of 2309 fetuses in our reference, 690 (30%) met the standard's inclusion criteria. There were no meaningful differences between the EFW distributions of the reference and standard curves (50th percentile: 1989 g reference vs. 1968 g standard; 10th percentile: 1711 g reference vs. 1710 g standard), or the proportion of small for gestational age fetuses (both 9.9%).

CONCLUSIONS

In our study, there was little practical difference between a fetal growth reference and standard for detecting small infants.

Preventing term stillbirth: benefits and limitations of using fetal growth reference charts

PURPOSE OF REVIEW

This review examines the variation in clinical practice with regards to ultrasound estimation of fetal weight, as well as calculation of fetal weight centiles.

RECENT FINDINGS

Placental dysfunction is associated with fetal smallness from intrauterine malnutrition as well as fetal disability and even stillbirth from hypoxemia. Although estimating fetal weight can be done accurately, the issue of which fetal weight centile chart should be used continues to be a contentious topic. The arguments against local fetal growth charts based on national borders and customization for variables known to be associated with disease are substantial. As for other human diseases such as hypertension and diabetes, there is a rationale for the use of an international fetal growth reference standard. Irrespective of the choice of fetal growth reference standard, a significant limitation of small for gestational age (SGA) detection programs to prevent stillbirth is that the majority of stillborn infants at term were not SGA at the time of demise.

SUMMARY

Placental dysfunction can present with SGA from malnutrition and/or stillbirth from hypoxemia depending on the gestational age of onset. Emerging data show that at term, fetal Doppler arterial redistribution is associated more strongly with perinatal death than fetal size. Properly conducted trials of the role for maternal characteristics, fetal size, placental biomarkers, and Doppler assessing fetal well-being are required urgently.

Validation of Delphi procedure consensus criteria for defining fetal growth restriction

OBJECTIVE

Recently, a Delphi procedure was used to establish new criteria for defining fetal growth restriction (FGR). These criteria require clinical validation. We sought to validate the Delphi consensus criteria by comparing their performance with that of our current definition (estimated fetal weight (EFW) < 10^th percentile) in predicting adverse neonatal outcome (ANO).

METHODS

This was a secondary analysis of data from a prospective cohort study of women referred for fetal growth assessment between 26 and 36 weeks' gestation. The current standard definition of FGR used in our clinical practice is EFW < 10^th percentile using Hadlock's fetal growth standard. The Delphi consensus criteria for FGR include either a very small fetus (abdominal circumference (AC) or EFW < 3^rd percentile) or a small fetus (AC or EFW < 10^th percentile) with additional abnormal Doppler findings or a decrease in AC or EFW by two quartiles or more. The primary outcome was the prediction of a composite of ANO including one or more of: admission to the neonatal intensive care unit, cord pH < 7.1, 5-min Apgar score < 7, respiratory distress syndrome, intraventricular hemorrhage, neonatal seizures or neonatal death. The discriminatory capacities of the two definitions of FGR for composite ANO and delivery of a small-for-gestational-age (SGA) neonate, defined as birth weight < 10^th percentile, were compared using area under the receiver-operating-characteristics curve (AUC). The sensitivity, specificity and predictive values of the methods were also compared.

RESULTS

Of 1055 pregnancies included in the study, composite ANO occurred in 139 (13.2%). There were only two cases of early FGR (before 32 weeks); therefore, the study focused on late FGR. Our current FGR diagnostic criterion of EFW < 10^th percentile was not associated significantly with composite ANO (relative risk (RR), 1.1 (95% CI, 0.6-1.8)), while the Delphi FGR criteria were (RR, 2.0 (95% CI, 1.2-3.3)). Our current definition of FGR showed higher discriminatory ability in the prediction of a SGA neonate (AUC, 0.69 (95% CI, 0.65-0.73)) than did the Delphi definition (AUC, 0.64 (95% CI, 0.60-0.67)) (P = 0.001). The AUCs of both definitions were poor for the prediction of composite ANO, despite slightly improved performance using the Delphi consensus definition of FGR (AUC, 0.53 (95% CI, 0.50-0.55)) compared with that of our current definition (AUC, 0.50 (95% CI, 0.48-0.53)) (P = 0.02).

CONCLUSION

The newly postulated criteria for defining FGR based on a Delphi procedure detects fewer cases of neonatal SGA than does our current definition of EFW < 10^th percentile, but is associated with a slight improvement in predicting ANO. Copyright © 2020 ISUOG. Published by John Wiley & Sons Ltd.

Fetal Growth Restriction Prediction: How to Move beyond

The actual burden and future burden of the small-for-gestational-age (SGA) babies turn their screening in pregnancy a question of major concern for clinicians and policymakers. Half of stillbirths are due to growth restriction in utero, and possibly, a quarter of livebirths of low- and middle-income countries are SGA. Growing body of evidence shows their higher risk of adverse outcomes at any period of life, including increased rates of neurologic delay, noncommunicable chronic diseases (central obesity and metabolic syndrome), and mortality. Although there is no consensus regarding its definition, birthweight centile threshold, or follow-up, we believe birthweight <10th centile is the most suitable cutoff for clinical and epidemiological purposes. Maternal clinical factors have modest predictive accuracy; being born SGA appears to be of transgenerational heredity. Addition of ultrasound parameters improves prediction models, especially using estimated fetal weight and abdominal circumference in the 3rd trimester of pregnancy. Placental growth factor levels are decreased in SGA pregnancies, and it is the most promising biomarker in differentiating angiogenesis-related SGA from other causes. Unfortunately, however, only few societies recommend universal screening. SGA evaluation is the first step of a multidimensional approach, which includes adequate management and long-term follow-up of these newborns. Apart from only meliorating perinatal outcomes, we hypothesize SGA screening is a key for socioeconomic progress.

Could masking gestational age estimation during scanning improve detection of small-for-gestational-age fetuses? A controlled pre-post evaluation

BACKGROUND

Antenatal detection of small-for-gestational-age fetuses improves outcomes and reduces perinatal mortality rates. However, ultrasonographic estimation of fetal weight is subject to several potential sources of error. One potential source of error is subconscious operator bias towards "normal" measurement values for gestational age (observer-expectancy bias).

OBJECTIVE

We aimed to determine whether the sensitivity of small-for-gestational-age detection is improved by removing real-time display of estimated gestational age during measurement of the abdominal circumference in the third trimester.

STUDY DESIGN

This retrospective evaluation (November 2014-May 2018 inclusive) included all singleton infants liveborn at ≥28 weeks gestation in a single United Kingdom obstetrics center. In the preintervention phase, real-time estimated gestational age was displayed to sonographers as they measured fetal abdominal circumference (the key determinant of estimated fetal weight with the use of the INTERGROWTH 21st fetal weight equation) in the third trimester. In the postintervention phase, real-time gestational age information was removed on selected ultrasound machines. Accuracy of birthweight percentile estimation was assessed before and after intervention, both in the full cohort comprising all eligible scans and in a subcohort that was scanned within 4 weeks of delivery. We assessed the accuracy of small-for-gestational-age detection using the sensitivity, positive likelihood ratio, and area under the receiver-operator curve.

RESULTS

Of the 18,342 eligible pregnancies, 9342 (51%) had a third-trimester growth scan. The sensitivity of ultrasonographic estimation of fetal weight for antenatal detection of small-for-gestational-age babies did not change significantly between the before and after intervention phases (31.5% confidence interval, 27.1-36.2 vs 31.7% confidence interval, 20.2-45.0). Although the sensitivity for small-for-gestational-age detection was higher in the subcohort that was scanned within 4 weeks of delivery than in the full cohort (P<.001), there was no significant difference between the before and after intervention phases (58% confidence interval, 50-66 vs 65% confidence interval, 43-84). With the use of an estimation of the abdominal circumference percentile rather than estimated fetal weight percentile significantly decreased the sensitivity for small-for-gestational-age detection in all groups (P<.01), but there was no difference between the before and after intervention phases.

CONCLUSION

Blinding operators to the estimated gestation of the fetus during abdominal circumference measurement does not significantly alter the antenatal detection rate of small-for-gestational-age babies. The observer-expectancy effect is therefore unlikely to be a significant contributor to the error that is associated with ultrasonographic estimation of fetal weight.

Implementing the INTERGROWTH-21st gestational dating and fetal and newborn growth standards in peri-urban Nairobi, Kenya: Provider experiences, uptake and clinical decision-making

BACKGROUND

Perinatal and newborn complications are major risk factors for unfavorable fetal and neonatal outcomes. Gestational dating and growth monitoring can be instrumental in the identification and management of high-risk pregnancies and births. The INTERGROWTH-21st Project developed the first global standards for gestational dating and fetal and newborn growth monitoring, supplying a toolkit for clinicians. This study aimed to assess the feasibility and acceptability of the first known implementation study of these standards in a low resource setting.

METHODS

The study was performed in two 12-month phases from March 2016 to March 2018 at Jacaranda Health, a private maternity hospital in peri-urban Nairobi, Kenya. In-depth interviews, focus group discussions and a provider survey were utilized to evaluate providers' experiences during implementation. Client chart data, for pregnant women attending antenatal care and/or delivering at Jacaranda Health along with their newborns, were captured to assess uptake and effect of the standards on clinical decision-making.

RESULTS

Facility-level support and provider buy-in proved to be critical factors driving the success of implementing the standards. However, additional support was needed to strengthen capacity to conduct and interpret ultrasounds and maintain motivation among providers. We observed a significant increase in the uptake of obstetric ultrasounds, particularly gestational dating, during the implementation of the standards. Although no significant changes were detected in the identification of high-risk pregnancies, referrals and deliveries by Cesarean section during implementation, we did observe a significant reduction in inductions for post-date. No significant barriers were reported regarding the use of the newborn standards. Over 80% of providers advocated for the standards to remain in place with some enhancements related mainly to training, advocacy and procurement.

CONCLUSIONS

The findings are timely with increasing global adoption of the standards and the challenging and multi-faceted nature of translating new, evidence-based guidelines into routine clinical practice.

Comparing INTERGROWTH-21st Century and Hadlock growth standards to predict small for gestational age and short-term neonatal outcomes

Objective: To compare the INTERGROWTH-21st Century growth standard to the Hadlock standard in predicting small for gestational age (SGA) and adverse neonatal outcomes.Method: This is a prospective cohort study on women with singleton gestations referred for fetal growth ultrasound between 26.0 and 36.6 weeks gestational age (GA). The primary outcome is prediction of neonatal SGA. Neonatal SGA was defined as birthweight <10th percentile for GA by Alexander chart. The discriminatory ability of the growth standards was compared using area under receiver operating characteristic curves (AUC).Results: Among 1054 patients who met inclusion criteria, 139 (13.2%) had neonatal SGA. The mean interval between estimated fetal weight and birthweight was 6.7 ± 3.1 weeks. Composite adverse neonatal outcome was seen in 300 (28.4%) patients. The sensitivity for identifying SGA neonates was higher for Hadlock compared with INTERGROWTH-21st standard (41.7 vs. 24.5%); AUC (95% CI) were 0.69 (0.65-0.73) and 0.62 (0.58-0.65), respectively. Both standards were comparable in predicting the composite adverse neonatal outcomes; AUC (95% CI) were 0.52 (0.50-0.53) and 0.52 (0.50-0.54), respectively; p = .28.Conclusions: The Hadlock standard had a moderate but higher discriminatory ability for predicting neonatal SGA compared to the INTERGROWTH-21st project standard. However, the two standards were poor predictors of early adverse neonatal outcomes.Rationale: The Intergrowth-21st project was recently introduced with the goal of providing a universal benchmark for comparing growth across different ethnicity. We performed a prospective cohort study to compare the Intergrowth-21st standard with the commonly used Hadlock standard for predicting pregnancies at risk for neonatal SGA and adverse outcomes. Hadlock fetal growth standard is moderately superior at predicting neonatal SGA compared to the Intergrowth-21st standard. Both standards are poor at predicting adverse neonatal outcomes. These findings, however, need further validation.

INTERGROWTH-21st compared with GROW customized centiles in the detection of adverse perinatal outcomes at term

Background: INTERGROWTH-21st charts provide standards for infants born under optimal pregnancy conditions. However, their validity in a general obstetric population is unclear. We aimed to identify whether INTERGROWTH-21st charts, compared with gestation related optimal weight (GROW) charts customized on maternal height, weight, and parity, better identified the at-risk infant.Methods: We performed a retrospective cohort analysis of all term women who gave birth at a single tertiary obstetric center during the period 1994-2016. Routinely collected maternity data was used for analysis. The primary outcome was an Apgar score <7 at 5 min. Secondary outcomes included Apgar score <5 at 5 min, stillbirth or admission to the neonatal intensive care unit (NICU). Populations of newborns were identified as SGA by: (a) INTERGROWTH-21st <10th centile (SGA_IG10th); (b) INTERGROWTH-21st z-score < -1 (SGA_IGzscore); and (c) GROW customized charts <10th (SGA_cust). The subgroups identified by only one chart were also specifically examined. Each SGA group was compared to infants appropriate for gestational age (AGA) on all charts (non-SGA).Results: Data for 71,487 births were available for analysis after exclusion of women with missing height or weight data. Only 3280 (4.6%) newborns were considered SGA_IG10th, with 5878 (8.2%) SGA_IGzscore and 7599 (10.6%) SGA_cust. INTERGROWTH-21st identified only 110 additional infants (0.15%) that were not identified by customized charts; none of these experienced any adverse outcomes. Customized centiles identified a further 4429 (6.2%) SGA infants (SGA_cust-only) that were not identified as SGA_IG10th, and who did demonstrate an increased risk of Apgar score <7 (OR 1.33, 95%CI 1.08-3.28) and stillbirth (OR 2.47, 95%CI 1.41-4.44) compared to the non-SGA infant. Significantly more obese women had infants considered SGA_cust (19.3%) than SGA_IG10th (10.0%) or SGA_IGzscore (9.9%).Conclusions: Amongst our general obstetric study population, the 10th centile of INTERGROWTH-21st identified only 4.6% of infants as SGA and was less likely to identify infants of obese women as SGA. Customized centiles identified almost all SGA-IG infants, including an additional group (SGA_cust-only) at higher risk of stillbirth and adverse outcomes compared with non-SGA infants.