Evaluation of the INTERGROWTH-21st project newborn standard for use in Canada

Differences When Classifying Small for Gestational Age Preterm Infants According to the Growth Chart Applied

OBJECTIVE

Consensus around the ideal chart to classify preterm babies is scant. It is particularly relevant in small for gestational age (SGA) infants due to its clinical and therapeutic implications. The aim of the study was to compare Olsen, Intergrowth-21st, and Fenton growth charts, regarding the classification at birth and incidence of SGA preterm infants.

STUDY DESIGN

Retrospective study of 529 preterm infants ≤ 32 weeks of gestational age. Birth weight Z-score was calculated applying the three growth charts and ponderal index (PI) was also estimated. Incidence of SGA (birth weight < 10th percentile) and clinical outcome were compared according to the chart used.

RESULTS

Incidence of SGA was significantly higher (p < 0.001) with Olsen (101 cases, 19.1%) compared with Intergrowth-21st (75 cases, 14.2%) and Fenton (53 cases, 10%). Differences were also found with PI of SGA preterm infants, as those infants classified by Olsen were mostly symmetric (PI > 10th percentile), while Fenton and Intergrowth-21st identified less symmetric SGA infants. Kappa concordance between Intergrowth-21st and Fenton was 0.805, Intergrowth-21st versus Olsen 0.824, and Fenton versus Olsen 0.641. No differences were observed on neonatal morbidities or mortality.

CONCLUSION

Significant differences were detected when classifying very preterm infants at birth according to the growth chart, mainly among symmetric SGA. Concordance between Fenton and Olsen was poor, but Intergrowth-21st showed high concordance with Fenton and Olsen. However, further research is needed to select the ideal chart. Variability in the population selected to create the curves and the accuracy dating the pregnancy are factors that may have explained differences.

KEY POINTS

· Very preterm infants are differently classified at birth with various growth charts.. · Higher incidence of small for gestational age infants with Olsen compared with Fenton or Intergrowth.. · Variability in population selection and accuracy in dating pregnancy may have explained differences..

The clinical performance and population health impact of birthweight-for-gestational age indices at term gestation

BACKGROUND

The assessment of birthweight for gestational age and the identification of small- and large-for-gestational age (SGA and LGA) infants remain contentious, despite the recent creation of the Intergrowth 21st Project and World Health Organisation (WHO) birthweight-for-gestational age standards.

OBJECTIVE

We carried out a study to identify birthweight-for-gestational age cut-offs, and corresponding population-based, Intergrowth 21st and WHO centiles associated with higher risks of adverse neonatal outcomes, and to evaluate their ability to predict serious neonatal morbidity and neonatal mortality (SNMM) at term gestation.

METHODS

The study population was based on non-anomalous, singleton live births between 37 and 41 weeks' gestation in the United States from 2003 to 2017. SNMM included 5-min Apgar score <4, neonatal seizures, need for assisted ventilation, and neonatal death. Birthweight-specific SNMM was modelled by gestational week using penalised B-splines. The birthweights at which SNMM odds were minimised (and higher by 10%, 50% and 100%) were estimated, and the corresponding population, Intergrowth 21st, and WHO centiles were identified. The clinical performance and population impact of these cut-offs for predicting SNMM were evaluated.

RESULTS

The study included 40,179,663 live births and 991,486 SNMM cases. Among female singletons at 39 weeks' gestation, SNMM odds was lowest at 3203 g birthweight, and 10% higher at 2835 g and 3685 g (population centiles 11th and 82nd, Intergrowth centiles 17th and 88th and WHO centiles 15th and 85th). Birthweight cut-offs were poor predictors of SNMM, for example, the cut-offs associated with 10% and 50% higher odds of SNMM among female singletons at 39 weeks' gestation resulted in a sensitivity, specificity, and population attributable fraction of 12.5%, 89.4%, and 2.1%, and 2.9%, 98.4% and 1.3%, respectively.

CONCLUSIONS

Reference- and standard-based birthweight-for-gestational age indices and centiles perform poorly for predicting adverse neonatal outcomes in individual infants, and their associated population impact is also small.

Stillbirths: Contribution of preterm birth and size-for-gestational age for 125.4 million total births from nationwide records in 13 countries, 2000-2020

OBJECTIVE

To examine the contribution of preterm birth and size-for-gestational age in stillbirths using six 'newborn types'.

DESIGN

Population-based multi-country analyses.

SETTING

Births collected through routine data systems in 13 countries.

SAMPLE

125 419 255 total births from 22+0 to 44+6 weeks' gestation identified from 2000 to 2020.

METHODS

We included 635 107 stillbirths from 22+0  weeks' gestation from 13 countries. We classified all births, including stillbirths, into six 'newborn types' based on gestational age information (preterm, PT, <37+0  weeks versus term, T, ≥37+0  weeks) and size-for-gestational age defined as small (SGA, <10th centile), appropriate (AGA, 10th-90th centiles) or large (LGA, >90th centile) for gestational age, according to the international newborn size for gestational age and sex INTERGROWTH-21st standards.

MAIN OUTCOME MEASURES

Distribution of stillbirths, stillbirth rates and rate ratios according to six newborn types.

RESULTS

635 107 (0.5%) of the 125 419 255 total births resulted in stillbirth after 22+0  weeks. Most stillbirths (74.3%) were preterm. Around 21.2% were SGA types (PT + SGA [16.2%], PT + AGA [48.3%], T + SGA [5.0%]) and 14.1% were LGA types (PT + LGA [9.9%], T + LGA [4.2%]). The median rate ratio (RR) for stillbirth was highest in PT + SGA babies (RR 81.1, interquartile range [IQR], 68.8-118.8) followed by PT + AGA (RR 25.0, IQR, 20.0-34.3), PT + LGA (RR 25.9, IQR, 13.8-28.7) and T + SGA (RR 5.6, IQR, 5.1-6.0) compared with T + AGA. Stillbirth rate ratios were similar for T + LGA versus T + AGA (RR 0.7, IQR, 0.7-1.1). At the population level, 25% of stillbirths were attributable to small-for-gestational-age.

CONCLUSIONS

In these high-quality data from high/middle income countries, almost three-quarters of stillbirths were born preterm and a fifth small-for-gestational age, with the highest stillbirth rates associated with the coexistence of preterm and SGA. Further analyses are needed to better understand patterns of gestation-specific risk in these populations, as well as patterns in lower-income contexts, especially those with higher rates of intrapartum stillbirth and SGA.

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.

Extrauterine Growth Restriction: Need for an Accurate Definition

Neonates show considerable variation in growth that can be recognized through serial measurements of basic variables such as weight, length, and head circumference. If possible, measurement of subcutaneous and total body fat mass can also be useful. These biometric measurements at birth may be influenced by demographics, maternal and paternal anthropometrics, maternal metabolism, preconceptional nutritional status, and placental health. Subsequent growth may depend on optimal feeding, total caloric intake, total metabolic activity, genetic makeup, postnatal morbidities, medications, and environmental conditions. For premature infants, these factors become even more important; poor in utero growth can be an important reason for spontaneous or induced preterm delivery. Later, many infants who have had intrauterine growth restriction (IUGR) and are born small for gestational age (SGA) continue to show suboptimal growth below the 10th percentile, a condition that has been defined as extrauterine growth restriction (EUGR) or postnatal growth restriction (PNGR). More importantly, a subset of these growth-restricted infants may also be at high risk of abnormal neurodevelopmental outcomes. There is a need for well-defined criteria to recognize EUGR/PNGR, so that correctional steps can be instituted in a timely fashion.

[Review of the literature on intrauterine and birthweight charts]

OBJECTIVES

To describe the main intrauterine and birthweight charts and review the studies comparing their performance for the identification of infants at risk of adverse perinatal outcomes.

METHODS

We carried out a literature search using Medline and selected the charts most frequently cited in the literature, French charts and those recently published.

RESULTS

Current knowledge on the association between mortality and morbidity and growth anomalies (small and large for gestational age) mostly relies on the use of descriptive charts which describe the weight distribution in unselected populations. Prescriptive charts, which describe ideal growth in low risk populations, have been constructed more recently. Few studies have evaluated whether the thresholds used to identify infants at risk with descriptive charts (such as the 3^rd or the 10^th percentile) are applicable to prescriptive charts. There is a large variability in the percentage of fetuses or newborns identified as being at risk by each chart, with from 3 to 25% having with a weight under the 10^th percentile, regardless of whether descriptive or prescriptive charts are used. The sensitivity and specificity of antenatal screening for small or large for gestational age newborns depends on the chart used to derive estimated fetal weight percentiles.

CONCLUSION

There is marked variability between intrauterine growth charts that can influence the percentage of infants identified as having abnormal growth. These results show that before the adoption of a growth chart, it is essential to evaluate whether it adequately describes the population and its performance for identifying of infants at risk because of growth anomalies.

The choice of reference chart affects the strength of the association between malaria in pregnancy and small for gestational age: an individual participant data meta-analysis comparing the Intergrowth-21 with a Tanzanian birthweight chart

BACKGROUND

The prevalence of small for gestational age (SGA) may vary depending on the chosen weight-for-gestational-age reference chart. An individual participant data meta-analysis was conducted to assess the implications of using a local reference (STOPPAM) instead of a universal reference (Intergrowth-21) on the association between malaria in pregnancy and SGA.

METHODS

Individual participant data of 6,236 newborns were pooled from seven conveniently identified studies conducted in Tanzania and Malawi from 2003-2018 with data on malaria in pregnancy, birthweight, and ultrasound estimated gestational age. Mixed-effects regression models were used to compare the association between malaria in pregnancy and SGA when using the STOPPAM and the Intergrowth-21 references, respectively.

RESULTS

The 10th percentile for birthweights-for-gestational age was lower for STOPPAM than for Intergrowth-21, leading to a prevalence of SGA_STOPPAM of 14.2% and SGA_IG21 of 18.0%, p < 0.001. The association between malaria in pregnancy and SGA was stronger for STOPPAM (adjusted odds ratio (aOR) 1.30 [1.09-1.56], p < 0.01) than for Intergrowth-21 (aOR 1.19 [1.00-1.40], p = 0.04), particularly among paucigravidae (SGA_STOPPAM aOR 1.36 [1.09-1.71], p < 0.01 vs SGA_IG21 aOR 1.21 [0.97-1.50], p = 0.08).

CONCLUSIONS

The prevalence of SGA may be overestimated and the impact of malaria in pregnancy underestimated when using Intergrowth-21. Comparing local reference charts to global references when assessing and interpreting the impact of malaria in pregnancy may be appropriate.

Associations of severe adverse perinatal outcomes among continuous birth weight percentiles on different birth weight charts: a secondary analysis of a cluster randomized trial

Objective

To identify neonatal risk for severe adverse perinatal outcomes across birth weight centiles in two Dutch and one international birth weight chart.

Background

Growth restricted newborns have not reached their intrinsic growth potential in utero and are at risk of perinatal morbidity and mortality. There is no golden standard for the confirmation of the diagnosis of fetal growth restriction after birth. Estimated fetal weight and birth weight below the 10^th percentile are generally used as proxy for growth restriction. The choice of birth weight chart influences the specific cut-off by which birth weight is defined as abnormal, thereby triggering clinical management. Ideally, this cut-off should discriminate appropriately between newborns at low and at high risk of severe adverse perinatal outcomes and consequently correctly inform clinical management.

Methods

This is a secondary analysis of the IUGR Risk Selection (IRIS) study. Newborns (n = 12 953) of women with a low-risk status at the start of pregnancy and that received primary antenatal care in the Netherlands were included.

We examined the distribution of severe adverse perinatal outcomes across birth weight centiles for three birth weight charts (Visser, Hoftiezer and INTERGROWTH) by categorizing birth weight centile groups and comparing the prognostic performance for severe adverse perinatal outcomes.

Severe adverse perinatal outcomes were defined as a composite of one or more of the following: perinatal death, Apgar score < 4 at 5 min, impaired consciousness, asphyxia, seizures, assisted ventilation, septicemia, meningitis, bronchopulmonary dysplasia, intraventricular hemorrhage, periventricular leukomalacia, or necrotizing enterocolitis.

Results

We found the highest rates of severe adverse perinatal outcomes among the smallest newborns (< 3^rd percentile) (6.2% for the Visser reference curve, 8.6% for the Hoftiezer chart and 12.0% for the INTERGROWTH chart). Discriminative abilities of the three birth weight charts across the entire range of birth weight centiles were poor with areas under the curve ranging from 0.57 to 0.61. Sensitivity rates of the various cut-offs were also low.

Conclusions

The clinical utility of all three charts in identifying high risk of severe adverse perinatal outcomes is poor. There is no single cut-off that discriminates clearly between newborns at low or high risk.

Trial Registration

Netherlands Trial Register NTR4367.

Registration date March 20^th, 2014.

A comparison of four fetal biometry growth charts within an Australian obstetric population

PURPOSE

The aim of this study was to investigate the applicability of four existing fetal growth charts to a local tertiary hospital obstetric population.

METHOD

Four existing fetal growth charts (the Raine study reference charts, INTERGROWTH-21st charts, World Health Organization (WHO) fetal growth study charts and Australasian Society for Ultrasound in Medicine (ASUM) endorsed Campbell Westerway charts were compared using data from 11651 singleton pregnancy ultrasound scans at King Edward Memorial Hospital (KEMH). The 3rd, 10th, 50th 90th and 97th percentile curves for abdominal circumference (AC) biometry for the KEMH data were calculated and the four primary correlation parameters from fitted 3rd order polynomials (a, b, c and d) were used to generate like-for-like comparisons for all charts.

RESULTS

The overall comparisons showed a significant variation with different growth charts, giving different percentiles for the same fetal AC measurement. INTERGROWTH-21st percentile curves tended to fall below those of other charts for AC measurements. Both the Raine Study charts and ASUM charts were the charts of closest overall fit to the local data.

CONCLUSION

Our data show the Raine Study charts are the most appropriate for our population compared with the other three charts assessed suggesting the 'one size fits all' model may not be appropriate. However, additional analysis of biometry measurements, primarily AC, is needed to address the deficiency of data at 14-18 weeks gestation which exists for the Raine Study data.A reasonable alternative may be to adopt the WHO charts with local calibration (including the 14 - 18 week gestation period).

International versus national growth charts for identifying small and large-for-gestational age newborns: A population-based study in 15 European countries

BACKGROUND

To inform the on-going debate about the use of universal prescriptive versus national intrauterine growth charts, we compared perinatal mortality for small and large-for-gestational-age (SGA/LGA) infants according to international and national charts in Europe.

METHODS

We classified singleton births from 33 to 42 weeks of gestation in 2010 and 2014 from 15 countries (N = 1,475,457) as SGA (birthweight <10th percentile) and LGA (>90th percentile) using the international Intergrowth-21st newborn standards and national charts based on the customised charts methodology. We computed sex-adjusted odds ratios (aOR) for stillbirth, neonatal and extended perinatal mortality by this classification using multilevel models.

FINDINGS

SGA and LGA prevalence using national charts were near 10% in all countries, but varied according to international charts with a north to south gradient (3.0% to 10.1% and 24.9% to 8.0%, respectively). Compared with appropriate for gestational age (AGA) infants by both charts, risk of perinatal mortality was increased for SGA by both charts (aOR[95% confidence interval (CI)]=6.1 [5.6-6.7]) and infants reclassified by international charts from SGA to AGA (2.7 [2.3-3.1]), but decreased for those reclassified from AGA to LGA (0.6 [0.4-0.7]). Results were similar for stillbirth and neonatal death.

INTERPRETATION

Using international instead of national charts in Europe could lead to growth restricted infants being reclassified as having normal growth, while infants with low risks of mortality could be reclassified as having excessive growth.

FUNDING

InfAct Joint Action, CHAFEA Grant n°801,553 and EU/EFPIA Innovative Medicines Initiative 2 Joint Undertaking ConcePTION grant n°821,520. AH received a PhD grant from EHESP.

Fenton vs. Intergrowth-21st: Postnatal Growth Assessment and Prediction of Neurodevelopment in Preterm Infants

Although the survival rate of preterm infants has improved over the years, growth failure and associated impaired neurodevelopmental outcome remains a significant morbidity. Optimal nutrition plays an important role in achieving adequate postnatal growth. Accurate growth monitoring of preterm infants is critical in guiding nutritional protocols. Currently, there is no consensus regarding which growth assessment tool is suitable for monitoring postnatal growth of preterm infants to foster optimal neurodevelopmental outcomes while avoiding future consequences of aggressive nutritional approaches including increased risk for cardiovascular disease and metabolic syndrome. A retrospective single center cohort study was conducted to compare the performance of two growth-assessment tools, Fenton and Intergrowth-21st (IG-21st) in the classification of size at birth, identification of impaired growth and predicting neurodevelopment. A total of 340 infants with mean gestational age of 30 weeks were included. Proportion of agreement between the two tools for identification of small for gestational age (SGA) was high 0.94 (0.87, 0.1) however, agreement for classification of postnatal growth failure at discharge was moderate 0.6 (0.52, 0.69). Growth failure at discharge was less prevalent using IG-21st. There was significant association between weight-based growth failure and poor neurodevelopmental outcomes at 12 and 24 months of age.

Performance of six birth-weight and estimated-fetal-weight standards for predicting adverse perinatal outcome: a 10-year nationwide population-based study

OBJECTIVE

To evaluate three birth-weight (BW) standards (Australian population-based, Fenton and INTERGROWTH-21^st ) and three estimated-fetal-weight (EFW) standards (Hadlock, INTERGROWTH-21^st and WHO) for classifying small-for-gestational age (SGA) and large-for-gestational age (LGA) and predicting adverse perinatal outcomes in preterm and term babies.

METHODS

This was a nationwide population-based study conducted on a total of 2.4 million singleton births that occurred from 24 + 0 to 40 + 6 weeks' gestation between 2004 and 2013 in Australia. The performance of the growth charts was evaluated according to SGA and LGA classification, and relative risk (RR) and diagnostic accuracy based on the areas under the receiver-operating-characteristics curves (AUCs) for stillbirth, neonatal death, perinatal death, composite morbidity and a composite of perinatal death and morbidity outcomes. The analysis was stratified according to gestational age at delivery (< 37 + 0 vs ≥ 37 + 0 weeks).

RESULTS

Following exclusions, 2 392 782 singleton births were analyzed. There were significant differences in the SGA and LGA classification and risk of adverse outcomes between the six BW and EFW standards evaluated. For the term group, compared with the other standards, the INTERGROWTH-21^st BW and EFW standards classified half the number of SGA (< 10^th centile) babies (3-4% vs 7-11%) and twice the number of LGA (> 90^th centile) babies (24-25% vs 8-15%), resulting in a smaller cohort of term SGA at higher risk of adverse outcome and a larger LGA cohort at lower risk of adverse outcome. For term SGA (< 3^rd centile) babies, the RR of perinatal death using the two INTERGROWTH-21^st standards was up to 1.5-fold higher than those of the other standards (including the WHO-EFW and Hadlock-EFW), while the INTERGROWTH-21^st -EFW standard indicated a 12-26% reduced risk of perinatal death for LGA cases across centile thresholds. Conversely, for the preterm group, the WHO-EFW and Hadlock-EFW standards identified a higher SGA classification rate than did the other standards (18-19% vs 10-11%) and a 20-65% increased risk of perinatal death in term LGA babies. All BW and EFW charts had similarly poor performance in predicting adverse outcomes, including the composite outcome (AUC range, 0.49-0.62) for both preterm (AUC range, 0.58-0.62) and term (AUC range, 0.49-0.50) cases and across centiles. Furthermore, specific centile thresholds for identifying adverse outcomes varied markedly by chart between BW and EFW standards.

CONCLUSIONS

This study addresses the recurrent problem of identifying fetuses at risk of morbidity and perinatal mortality associated with growth disorders and provides new insights into the applicability of international growth standards. Our findings of marked variation in classification and the similarly poor performance of prescriptive international standards and the other commonly used standards raise questions about whether the prescriptive international standards that were constructed for universal adoption are indeed applicable to a multiethnic population such as that of Australia. Thus, caution is needed when adopting universal standards for clinical and epidemiological use. © 2020 International Society of Ultrasound in Obstetrics and Gynecology.

Is the Intrauterine INTERGROWTH-21 Growth Curve Better Than Fenton's for the Classification at Birth and Prediction of Postnatal Growth in Preterm Infants?

OBJECTIVE

To compare the classification of the adequacy of birth weight for gestational age applying INTERGROWTH-21 (IG-21) and Fenton growth curves in preterm infants, and to relate this classification to the nutritional status at 12 months corrected age.

METHODS

This is a retrospective study with 173 preterm infants aged between 26 and 33 weeks. Data was collected on maternal health conditions, birth and gestational age anthropometric information, and anthropometry (weight, height, and head circumference) at 12 months corrected age.

RESULTS

The mean birth weight and gestational age were 1151.4 ± 227.2 g and 30.2 ± 2.4 weeks, respectively. Using percentiles of IG-21 and Fenton curves, the proportion of SGA and LGA preterm infants was 39.2% vs. 35.2%, and 3.5% vs. 3.5%, respectively (p = 0.520). At 12 months corrected age, short stature, overweight, and thinness were observed in 33.5%, 9.9%, and 11% of preterm infants, respectively. The ROC curve evidenced that the IG-21 was slightly better than Fenton to predict short stature (AUC = 0.626, 95% CI 0.537-0.715 and AUC = 0.600, 95% CI 0.506-0.694) and overweight (AUC = 0.648, 95% CI 0.527-0.769 and AUC = 0.618, 95% CI 0.486-0.750) at 12 months corrected age. In contrast, the ROC curve did not show an association of IG-21 and Fenton percentiles with thinness.

CONCLUSIONS FOR PRACTICE

This study showed that IG-21 and Fenton were similar for the classification of birth weight for gestational age in preterm infants. IG-21 was slightly better than Fenton to predict overweight and short stature in preterm infants at 12 months corrected age.

Reassessment of the risk of birth defects due to Zika virus in Guadeloupe, 2016

BACKGROUND

In the French Territories in the Americas (FTA), the risk of birth defects possibly associated with Zika virus (ZIKV) infection was 7.0% (95%CI: 5.0 to 9.5) among foetuses/infants of 546 women with symptomatic RT-PCR confirmed ZIKV infection during pregnancy. Many of these defects were isolated measurement-based microcephaly (i.e. without any detected brain or clinical abnormalities) or mild neurological conditions. We wanted to estimate the proportion of such minor findings among live births of women who were pregnant in the same region during the outbreak period but who were not infected with ZIKV.

METHODS

In Guadeloupe, pregnant women were recruited at the time of delivery and tested for ZIKV infection. The outcomes of live born infants of ZIKV non-infected women were compared to those of ZIKV-exposed live born infants in Guadeloupe, extracted from the FTA prospective cohort.

RESULTS

Of 490 live born infants without exposure to ZIKV, 42 infants (8.6%, 95%CI: 6.2-11.4) had mild abnormalities that have been described as 'potentially linked to ZIKV infection'; all but one of these was isolated measurement-based microcephaly. Among the 241 live born infants with ZIKV exposure, the proportion of such abnormalities, using the same definition, was similar (6.6%, 95%CI: 3.8-10.6).

CONCLUSIONS

Isolated anthropometric abnormalities and mild neurological conditions were as prevalent among infants with and without in-utero ZIKV exposure. If such abnormalities had not been considered as 'potentially linked to ZIKV' in the original prospective cohort in Guadeloupe, the overall estimate of the risk of birth defects considered due to the virus would have been significantly lower, at approximately 1.6% (95% CI: 0.4-4.1).

TRIAL REGISTRATION

ClinicalTrials.gov (NCT02916732).

The impact of optimal dating on the assessment of fetal growth

BACKGROUND

The impact of using the Intergrowth (IG) dating formulae in comparison to the commonly used Robinson dating on the evaluation of biometrics and estimated fetal weight (EFW) has not been evaluated.

METHODS

Nationwide cross-sectional study of routine fetal ultrasound biometry in low-risk pregnant women whose gestational age (GA) had been previously assessed by a first trimester CRL measurement. We compared the CRL-based GA according to the Robinson formula and the IG formula. We evaluated the fetal biometric measurements as well as the EFW taken later in pregnancy depending on the dating formula used. Mean and standard deviation of the Z scores as well as the number and percentage of cases classified as <3rd, < 10th, >90th and > 97th percentile were compared.

RESULTS

Three thousand five hundred twenty-two low-risk women with scans carried out after 18 weeks were included. There were differences of zero, one and 2 days in 642 (18.2%), 2700 (76.7%) and 180 (5%) when GA was estimated based on the Robinson or the IG formula, respectively. The biometry Z scores assessed later in pregnancy were all statistically significantly lower when the Intergrowth-based dating formula was used (p < 10- 4). Likewise, the number and percentage of foetuses classified as <3rd, < 10th, >90th and > 97th percentile demonstrated significant differences. As an example, the proportion of SGA foetuses varied from 3.46 to 4.57% (p = 0.02) and that of LGA foetuses from 17.86 to 13.4% (p < 10- 4).

CONCLUSION

The dating formula used has a quite significant impact on the subsequent evaluation of biometry and EFW. We suggest that the combined and homogeneous use of a recent dating standard, together with prescriptive growth standards established on the same low-risk pregnancies, allows an optimal assessment of fetal growth.

Current use and performance of the different fetal growth charts in the Italian population

OBJECTIVES

The choice of growth charts impacts on screening, diagnosis and clinical management of fetal growth abnormalities. The objectives of the study were to evaluate: 1) the clinical practice at a national level among tertiary referral centers in the use of fetal biometric growth charts; and 2) the impact on fetal growth screening of existing national and international growth charts.

STUDY DESIGN

A questionnaire was sent to 14 Italian tertiary referral centers to explore biometric reference growth charts used in clinical practice. National and international (Intergrowth-21st and World Health Organization) fetal growth charts were tested on a large national cohort of low risk women with singleton uneventful pregnancy derived from a retrospective cross-sectional multicenter study (21 centers). The percentage of fetuses with biometric measurements below and above the 10th and 90th percentile for each biometric parameter and gestational week were calculated for each growth chart. The percentile curves of the study population were calculated by non-linear quantile regressions.

RESULTS

Twelve Italian centers (86 %) answered to the questionnaire showing a wide discrepancy in the use of growth charts for fetal biometry. The cohort included 7347 pregnant women. By applying Intergrowth-21st growth charts the percentage of fetuses with head circumference, abdominal circumference and femur length below the 10th centile was 3.9 %, 3.6 % and 2.3 %, and above the 90th centile 29.9 %, 32.5 % and 46 %, respectively. The percentages for the World Health Organization growth charts for head and abdominal circumferences and femur length were: below the 10th centile 6.3 %, 7.2 % and 5.3 %, and above 90th centile 22.8 %, 21.3 % and 31.9 %, respectively.

CONCLUSIONS

The wide discrepancy in clinical use of fetal growth charts in Italian centers warrants the adoption of an uniform set of charts. Our data suggest that immediate application into clinical practice of international growth charts might result into an under-diagnosis of small for gestational age fetuses and, especially, in an over-diagnosis of large for gestational age fetuses with major consequences for clinical practice. On these grounds, there is an urgent need for a nationwide study for the prospective evaluation of international growth charts and, if needed, the construction and adoption of methodologically robust national growth charts.

Performance of different fetal growth charts in prediction of large-for-gestational age and associated neonatal morbidity in multiethnic obese population

OBJECTIVES

To examine the performance of different fetal growth charts in the prediction of large-for-gestational age (LGA) and associated neonatal morbidity at term in a multiethnic, obese population.

METHODS

This was a retrospective cohort study of 253 non-anomalous, singleton, term pregnancies that underwent serial third-trimester ultrasound scans due to maternal body mass index ≥ 35 kg/m² . We compared the performance of the Hadlock, Gestation Related Optimal Weight (GROW), INTERGROWTH-21^st (IG-21), World Health Organization (WHO) and Fetal Medicine Foundation (FMF) fetal growth reference charts in the prediction of LGA at birth, defined as birth weight > 90^th percentile, and neonatal morbidity, defined as a composite of neonatal intensive care unit admission or 5-min Apgar score < 7.

RESULTS

In the study population, 53 (20.9%) infants were born LGA, 27 (10.7%) experienced neonatal morbidity and nine (3.6%) were LGA with associated neonatal morbidity. The Hadlock and GROW charts showed similar performance in predicting LGA, with sensitivity of 66.0% for both and specificity of 82.5% and 83.5%, respectively. The positive likelihood ratios (LR+) were 3.77 (95% CI, 2.64-5.40) and 4.00 (95% CI, 2.77-5.78), respectively. The IG-21, WHO and FMF charts performed similarly and had higher sensitivity of about 85%, with specificity between 66% and 72%. LR+ was 2.74 (95% CI, 2.16-3.47), 2.50 (95% CI, 2.00-3.12) and 3.03 (95% CI, 2.36-3.89), respectively. All charts had high sensitivity for predicting neonatal morbidity associated with LGA, with LR+ ranging between 2.35 and 3.61.

CONCLUSIONS

In our multiethnic, obese population, all fetal growth charts performed well in predicting LGA and associated neonatal morbidity. However, the choice of fetal reference chart is likely to affect intervention rates. Copyright © 2019 ISUOG. Published by John Wiley & Sons Ltd.

The pitfalls of using birthweight centile charts to audit care

Objectives

Timely delivery of fetal growth restriction (FGR) is important in reducing stillbirth. However, targeted earlier delivery of FGR preferentially removes smaller babies from later gestations, thereby right-shifting the distribution of birthweights at term. This artificially increases the birthweight cutoffs defining the lower centiles and redefines normally grown babies as small by population-based birthweight centiles. Our objective was to compare updated Australian national population-based birthweight centile charts over time with the prescriptive INTERGROWTH-21^st standard.

Methods

A retrospective descriptive study of all singleton births ≥34 weeks’ gestation in Victoria, Australia in five two-year epochs: 1983–84, 1993–94, 2003–04, 2013–14, and 2016–17. The birthweight cutoffs defining the 3^rd and 10^th centile from three Australian national population-based birthweight centile charts, for births in 1991–1994, in 1998–2007, and 2004–2013 respectively, were applied to each epoch to calculate the proportion of babies with birthweight <3^rd and <10^th centile. The same analysis was done using the INTERGROWTH-21^st birthweight standard. To assess change over gestation, proportions were also calculated at preterm, early term and late term gestations.

Results

From 1983–84 to 2016–17, the proportion of babies with birthweight <3^rd fell across all birthweight centile charts, from 3.1% to 1.7% using the oldest Australian chart, from 3.9% to 1.9% using the second oldest Australian chart, from 4.3% to 2.2% using the most recent Australian chart, and from 2.0% to 0.9% using the INTERGROWTH-21^st standard. A similar effect was evident for the <10^th centile. The effect was most obvious at term gestations. Updating the Australian population birthweight chart progressively right-shifted the birthweight distribution, changing the definition of small over time. The birthweight distribution of INTERGROWTH-21^st was left-shifted compared to the Australian charts.

Conclusions

Locally-derived population-based birthweight centiles are better for clinical audit of care but should not be updated. Prescriptive birthweight standards are less useful in defining ‘small’ due to their significant left-shift.

Composite neonatal morbidity indicators using hospital discharge data: A systematic review

BACKGROUND

Neonatal morbidity is associated with lifelong impairments, but the absence of a consensual definition and the need for large data sets limit research.

OBJECTIVES

To inform initiatives to define standard outcomes for research, we reviewed composite neonatal morbidity indicators derived from routine hospital discharge data.

DATA SOURCES

PubMed (updated on October 12, 2018). The search algorithm was based on three components: "morbidity," "neonatal," and "hospital discharge data."

STUDY SELECTION AND DATA EXTRACTION

Studies investigating neonatal morbidity using a composite indicator based on hospital discharge data were included. Indicators defined for specific conditions (eg congenital anomalies, maternal addictions) were excluded. The target population, objectives, component morbidities, diagnosis and procedure codes, validation methods, and prevalence of morbidity were extracted.

SYNTHESIS

For each study, we assessed construct validity by describing the methods used to select the indicator components and evaluated whether the authors assessed internal and external validity. We also calculated confidence intervals for the prevalence of the morbidity composite.

RESULTS

Seventeen studies fulfilled inclusion criteria. Indicators targeted all (n = 4), low-/moderate-risk (n = 9), and very preterm (VPT, n = 4) infants. Components were similar for VPT infants, but domains and diagnosis codes within domains varied widely for all and low-/moderate-risk infants. Component selection was described for 8/17 indicators and some form of validation reported for 12/17. Neonatal morbidity prevalence ranged from 4.6% to 9.0% of all infants, 0.4% to 8.0% of low-/moderate-risk infants, and 17.8% to 61.0% of VPT infants.

CONCLUSIONS

Multiple neonatal morbidity indicators based on hospital discharge data have been used for research, but their heterogeneity limits comparisons between studies. Standard neonatal outcome measures are needed for benchmarking and synthesis of research results.

Applying Methods for Postnatal Growth Assessment in the Clinical Setting: Evaluation in a Longitudinal Cohort of Very Preterm Infants

AIM

To analyze different methods to assess postnatal growth in a cohort of very premature infants (VPI) in a clinical setting and identify potential early markers of growth failure.

METHODS

Study of growth determinants in VPI (≤32 weeks) during hospital stay. Nutritional intakes and clinical evolution were recorded. Growth velocity (GV: g/kg/day), extrauterine growth restriction (%) (EUGR: weight < 10th centile, z-score < -1.28) and postnatal growth failure (PGF: fall in z-score > 1.34) at 36 weeks postmenstrual age (PMA) were calculated. Associations between growth and clinical or nutritional variables were explored (linear and logistic regression).

RESULTS

Sample: 197 VPI. GV in IUGR patients was higher than in non-IUGRs (28 days of life and discharge). At 36 weeks PMA 66.0% of VPIs, including all but one of the IUGR patients, were EUGR. Prevalence of PGF at the same time was 67.4% (IUGR patients: 48.1%; non-IUGRs: 70.5% (p = 0.022)). Variables related to PGF at 36 weeks PMA were initial weight loss (%), need for oxygen and lower parenteral lipids in the first week.

CONCLUSIONS

The analysis of z-scores was better suited to identify postnatal growth faltering. PGF could be reduced by minimising initial weight loss and assuring adequate nutrition in patients at risk.

Adverse perinatal outcomes in immigrants: A ten-year population-based observational study and assessment of growth charts

BACKGROUND

Maternity populations are becoming increasingly multiethnic. Conflicting findings exist regarding the risk of adverse perinatal outcomes among immigrant mothers from different world regions and which growth charts are most appropriate for identifying the risk of adverse outcomes.

OBJECTIVE

To evaluate whether infant mortality and morbidity, and the categorisation of infants as small for gestational age or large for gestational age (SGA or LGA) vary by maternal country of birth, and to assess whether the choice of growth chart alters the risk of adverse outcomes in infants categorised as SGA and LGA.

METHODS

A population cohort of 601 299 singleton infants born in Australia to immigrant mothers was compared with 1.7 million infants born to Australian-born mothers, 2004-2013. Infants were categorised as SGA and LGA according to a descriptive Australian population-based birthweight chart (Australia-2012 reference) and the prescriptive INTERGROWTH-21st growth standard. Propensity score reweighting was used for the analysis.

RESULTS

Compared to Australian-born infants, infants of mothers from Africa, Philippines, India, other Asia countries, and the Middle East had between 15.4% and 48.1% elevated risk for stillbirth, preterm delivery, or low Apgar score. The association between SGA and LGA and perinatal mortality varied markedly by growth chart and country of birth. Notably, SGA infants from African-born mothers had a relative risk of perinatal mortality of 6.1 (95% CI 4.3, 6.7) and 17.3 (95% CI 12.0, 25.0) by the descriptive and prescriptive charts, respectively. LGA infants born to Australian-born mothers were associated with a 10% elevated risk of perinatal mortality by the descriptive chart compared to a 15% risk reduction by the prescriptive chart.

CONCLUSIONS

Country-of-birth-specific variations are becoming increasingly important for providing ethnically appropriate and safe maternity care. Our findings highlight significant variations in risk of adverse perinatal outcomes in immigrant subgroups, and demonstrate how the choice of growth chart alters the quantification of risk associated with being born SGA or LGA.

Social gradient of birthweight in England assessed using the INTERGROWTH-21st gestational age-specific standard

OBJECTIVE

To determine the socioeconomic gradient of birthweights in England with reference to the prescriptive INTERGROWTH-21^st Birthweight Standard.

DESIGN

National cross-sectional study using data from Hospital Episode Statistics.

SETTING

National Health Service in England.

PARTICIPANTS

All singleton babies, live born between 34 weeks' gestation and 42 weeks' gestation, between 1 April 2011 and 31 March 2012.

MAIN OUTCOME MEASURES

Birthweight distribution of babies with a birthweight of <10th centile or >90th centile, that is, small for gestational age (SGA) or large for gestational age (LGA) using Index of Multiple Deprivation quintiles as a proxy for socioeconomic status.

RESULTS

Of 508 230 babies born alive between 1 April 2011 and 31 March 2012, 38 838 (7.6%) were SGA and 81 026 (15.9%) were LGA. Median birthweight was 3405 g, median z-score was 0.25 (SD 1.06). Birthweight z-score demonstrated a social gradient, from 0.26 (SD 1.1) in the most deprived areas to 0.53 (1.0) in the least deprived. Women in the most deprived areas were twice as likely to have SGA babies using the INTERGROWTH-21^st chart (OR 1.94; 95% CI 1.87 to 2.01) compared with those in the least deprived areas. If all women had the same rate of SGA equivalent to those living in the least deprived areas, approximately 12 410 (30%) fewer babies would be born SGA in England each year.

CONCLUSIONS

This study gives a measure of the social gradient in singleton SGA and LGA babies across England using an international standard of newborn size at birth.

Determination of birth-weight centile thresholds associated with adverse perinatal outcomes using population, customised, and Intergrowth charts: A Swedish population-based cohort study

BACKGROUND

Although many studies have compared birth-weight charts to determine which better identify infants at risk of adverse perinatal outcomes, less attention has been given to the threshold used to define small or large for gestational age (SGA or LGA) infants. Our aim was to explore different thresholds associated with increased risk of adverse perinatal outcomes using population, customised, and Intergrowth centile charts.

METHODS AND FINDINGS

This is a population-based cohort study (Swedish Medical Birth Registry), which included term singleton births between 2006 and 2015 from women with available data on first-trimester screening. Population, customised, and Intergrowth charts were studied. Outcomes included cesarean section, postpartum haemorrhage, severe perineal tear, Apgar score at 5 minutes, neonatal morbidity, and perinatal mortality. Odds for each outcome were assessed in intervals of 5 centiles of birth weight (reference being 40th-60th centiles) using logistic regression. Intervals of 5% of the population were also explored. Sensitivity for fixed false-positive rates (FPRs) was reported for neonatal outcomes. Data from 212,101 births were analysed. Mean age was 33 ± 5 years, 48% of women were nulliparous, and 80% were born in Sweden. Prevalence of SGA (<10th centile) was 10.1%, 10.0%, and 3.1%, and prevalence of LGA (>90th centile) was 10.0%, 8.2%, and 25.1%, assessed using population, customised, and Intergrowth charts, respectively. In small infants, the risk of perinatal mortality was consistently increased below the 15th, 10th, and 35th birth-weight centiles for the respective charts (odds ratio [OR] 1.59, 95% confidence interval [CI] 1.05-2.39, p = 0.03 for 10th-15th population centile; OR 2.54, 95% CI 1.74-3.71, p < 0.001 for 5th-10th customised centile; OR 1.81, 95% CI 1.07-3.04, p = 0.03 for 30th-35th Intergrowth centile). The strength of association with adverse perinatal outcomes was different between infants below the 5th birth-weight centile for each chart (OR 4.47, 95% CI 3.30-6.04, p < 0.001 for the population chart; OR 5.78, 95% CI 4.22-7.91, p < 0.001 for the customised chart; OR 10.74, 95% CI 7.32-15.77, p < 0.001 for the Intergrowth chart) but similar in the smallest 5% of the population (OR 4.34, 95% CI 3.22-5.86, p < 0.001 for the population chart; OR 5.23, 95% CI 3.85-7.11, p < 0.001 for the customised chart; OR 4.69, 95% CI 3.47-6.34, p < 0.001 for the Intergrowth chart). For a fixed FPR of 10%, different thresholds for each chart achieved similar sensitivity for perinatal mortality in small infants (29% for all charts). Similar behaviour of different thresholds and similar risk/sensitivity for fixed FPR were observed in relation to other outcomes and for LGA infants. Limitations of this study include the relative homogeneity of the Swedish population, which limits generalisability to other populations; customised centiles may perform differently in populations with increased heterogeneity of ethnic background.

CONCLUSIONS

The risk of adverse outcomes was consistent across proportions of the population but did not reflect fixed thresholds, such as the 10th or 90th centiles, across different growth charts. Chart-specific thresholds for the population should be considered in clinical practice.

Preterm newborn's postnatal growth patterns: how to evaluate them

OBJECTIVES

There are several factors that influence the postnatal growth of preterm infants. It is crucial to define how to evaluate the growth rate of each preterm child and its individual trajectory, the type of growth curve, either with parameters of prescriptive curves for healthy preterm infants with no morbidities or, in the case of preterm infants and their "bundle of vulnerabilities", growth curves that may represent how they are actually growing, with the aim of directing appropriate nutritional care to each gestational age range.

DATA SOURCES

The main studies with growth curves for growth monitoring and the appropriate nutritional adjustments that prioritized the individual trajectory of postnatal growth rate were reviewed. PubMed and Google Scholar were searched.

DATA SYNTHESIS

The use of longitudinal neonatal data with different gestational ages and considering high and medium-risk pregnancies will probably be essential to evaluate the optimal growth pattern.

CONCLUSIONS

Prioritizing and knowing the individual growth trajectory of each preterm child is an alternative for preterm infants with less than 33 weeks of gestational age. For larger preterm infants born at gestational age >33 weeks, the Intergrowth 21st curves are adequate.

Paternal contributions to large-for-gestational-age term babies: findings from a multicenter prospective cohort study

We assessed whether paternal demographic, anthropometric and clinical factors influence the risk of an infant being born large-for-gestational-age (LGA). We examined the data on 3659 fathers of term offspring (including 662 LGA infants) born to primiparous women from Screening for Pregnancy Endpoints (SCOPE). LGA was defined as birth weight >90th centile as per INTERGROWTH 21st standards, with reference group being infants ⩽90th centile. Associations between paternal factors and likelihood of an LGA infant were examined using univariable and multivariable models. Men who fathered LGA babies were 180 g heavier at birth (P<0.001) and were more likely to have been born macrosomic (P<0.001) than those whose infants were not LGA. Fathers of LGA infants were 2.1 cm taller (P<0.001), 2.8 kg heavier (P<0.001) and had similar body mass index (BMI). In multivariable models, increasing paternal birth weight and height were independently associated with greater odds of having an LGA infant, irrespective of maternal factors. One unit increase in paternal BMI was associated with 2.9% greater odds of having an LGA boy but not girl; however, this association disappeared after adjustment for maternal BMI. There were no associations between paternal demographic factors or clinical history and infant LGA. In conclusion, fathers who were heavier at birth and were taller were more likely to have an LGA infant, but maternal BMI had a dominant influence on LGA.

A Comparison of Prediction of Adverse Perinatal Outcomes between Hadlock and INTERGROWTH-21st Standards at the Third Trimester

Little is known about the clinical value of the Hadlock and INTERGROWTH-21^st EFW standards for predicting adverse perinatal outcomes (APOs) in the third trimester. The purpose of this study was to study the association between low estimated fetal weight percentile (EFWc) in the third trimester and the risk of APOs and compare predictions of APOs between Hadlock and INTERGROWTH-21^st EFW standards. A prospective cohort of 690 singleton pregnancies with ultrasonography performed in the third trimester between March 2015 and March 2016 in China was conducted. EFW and the corresponding EFWc were measured using the Hadlock and INTERGROWTH-21^st standards, respectively. Cox proportional hazard models were used to assess the relationship between low EFWc (i.e., <5 percentile, P5) and the risk of APOs. Compared with fetuses with ≥P5 of the EFWc, fetuses with <P5 of the EFWc were much more likely to have an APO, with adjusted hazard ratios of 35.0 (95% confidence interval, 13.9-88.5) and 17.5 (7.7-39.6) for the Hadlock and INTERGROWTH standards, respectively. The Hadlock-EFWc had a higher predictive accuracy for APOs than the INTERGROWTH-EFWc, with area under the receiver operating characteristic curve of 0.94 (0.92-0.95) and 0.90 (0.87-0.92), respectively (P=0.007). The cutoff value for the INTERGROWTH-EFWc was percentile 11.61 with a sensitivity and specificity of 87.9% and 80.5%, respectively. For the Hadlock-EFWc, the corresponding sensitivity and specificity were 93.9% and 81.2%, with a cutoff value of percentile 8.65. Fetuses with low EFWc (i.e., <P5) were associated with an increased risk of APOs. APOs were more accurately predicted when EFWc was measured by the Hadlock standard than by the INTERGROWTH-21^st standard.

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.