Development of birth weight for gestational age charts and comparison with currently used charts: defining growth in the Polish population

Stillbirth risk and smallness for gestational age according to Hadlock, INTERGROWTH-21st, WHO, and GROW fetal weight standards: analysis by maternal ethnicity and body mass index

BACKGROUND

Appropriate growth charts are essential for fetal surveillance, to confirm that growth is proceeding normally and to identify pregnancies that are at risk. Many stillbirths are avoidable through antenatal detection of the small-for-gestational-age fetus. In the absence of an international consensus on which growth chart to use, it is essential that clinical practice reflects outcome-based evidence.

OBJECTIVE

This study investigated the performance of 4 internationally used fetal weight standards and their ability to identify stillbirth risk in different ethnic and maternal size groups of a heterogeneous population.

STUDY DESIGN

We analyzed routinely collected maternity data from more than 2.2 million pregnancies. Three population-based fetal weight standards (Hadlock, Intergrowth-21st, and World Health Organization) were compared with the customized GROW standard that was adjusted for maternal height, weight, parity, and ethnic origin. Small-for-gestational-age birthweight and stillbirth risk were determined for the 2 largest ethnic groups in our population (British European and South Asian), in 5 body mass index categories, and in 4 maternal size groups with normal body mass index (18.5-25.0 kg/m2). The differences in trend between stillbirth and small-for-gestational-age rates were assessed using the Clogg z test, and differences between stillbirths and body mass index groups were assessed using the chi-square trend test.

RESULTS

Stillbirth rates (per 1000) were higher in South Asian pregnancies (5.51) than British-European pregnancies (3.89) (P<.01) and increased in both groups with increasing body mass index (P<.01). Small-for-gestational-age rates were 2 to 3-fold higher for South Asian babies than British European babies according to the population-average standards (Hadlock: 26.2% vs 12.2%; Intergrowth-21st: 12.1% vs 4.9%; World Health Organization: 32.2% vs 16.0%) but were similar by the customized GROW standard (14.0% vs 13.6%). Despite the wide variation, each standard's small-for-gestation-age cases had increased stillbirth risk compared with non-small-for-gestation-age cases, with the magnitude of risk inversely proportional to the rate of cases defined as small for gestational age. All standards had similar stillbirth risk when the small-for-gestation-age rate was fixed at 10% by varying their respective thresholds for defining small for gestational age. When analyzed across body mass index subgroups, the small-for-gestation-age rate according to the GROW standard increased with increasing stillbirth rate, whereas small-for-gestation-age rates according to Hadlock, Intergrowth-21st, and World Health Organization fetal weight standards declined with increasing body mass index, showing a difference in trend (P<.01) to stillbirth rates across body mass index groups. In the normal body mass index subgroup, stillbirth rates showed little variation across maternal size groups; this trend was followed by GROW-based small-for-gestation-age rates, whereas small-for-gestation-age rates defined by each population-average standard declined with increasing maternal size.

CONCLUSION

Comparisons between population-average and customized fetal growth charts require examination of how well each standard identifies pregnancies at risk of adverse outcomes within subgroups of any heterogeneous population. In both ethnic groups studied, increasing maternal body mass index was accompanied by increasing stillbirth risk, and this trend was reflected in more pregnancies being identified as small for gestational age only by the customized standard. In contrast, small-for-gestation-age rates fell according to each population-average standard, thereby hiding the increased stillbirth risk associated with high maternal body mass index.

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.

The Danish newborn standard and the International Fetal and Newborn Growth Consortium for the 21st Century newborn standard: a nationwide register-based cohort study

BACKGROUND

It is a matter of debate whether 1 universal standard, such as the International Fetal and Newborn Growth Consortium for the 21st Century standard, can be applied to all populations.

OBJECTIVE

The primary objective was to establish a Danish newborn standard based on the criteria of the International Fetal and Newborn Growth Consortium for the 21st Century standard to compare the percentiles of these 2 standards. A secondary objective was to compare the prevalence and risk of fetal and neonatal deaths related to small for gestational age defined by the 2 standards when used in the Danish reference population.

STUDY DESIGN

This was a register-based nationwide cohort study. The Danish reference population included 375,318 singletons born at 33 to 42 weeks of gestation in Denmark between January 1, 2008, and December 31, 2015. The Danish standard cohort included 37,811 newborns who fulfilled the criteria of the International Fetal and Newborn Growth Consortium for the 21st Century standard. Birthweight percentiles were estimated using smoothed quantiles for each gestational week. The outcomes included birthweight percentiles, small for gestational age (defined as a birthweight of 3rd percentile), and adverse outcomes (defined as either fetal or neonatal death).

RESULTS

At all gestational ages, the Danish standard median birthweights at term were higher than the International Fetal and Newborn Growth Consortium for the 21st Century standard median birthweights: 295g for females and 320 g for males. Therefore, the estimates of the prevalence rate of small for gestational age within the entire population were different: 3.9% (n=14,698) using the Danish standard vs 0.7% (n=2640) using the International Fetal and Newborn Growth Consortium for the 21st Century standard. Accordingly, the relative risk of fetal and neonatal deaths among small-for-gestational-age fetuses differed by SGA status defined by the different standards (4.4 [Danish standard] vs 9.6 [International Fetal and Newborn Growth Consortium for the 21st Century standard]).

CONCLUSION

Our finding did not support the hypothesis that 1 universal standard birthweight curve can be applied to all populations.

Prediction of Perinatal and Neurodevelopmental Outcomes in Newborns with a Birth Weight below the 3rd Percentile: Performance of Two International Curves - Prospective Cohort from a Brazilian City

OBJECTIVES

 To evaluate the performance of Intergrowth-21 st (INT) and Fetal Medicine Foundation (FMF) curves in predicting perinatal and neurodevelopmental outcomes in newborns weighing below the 3rd percentile.

METHODS

 Pregnant women with a single fetus aged less than 20 weeks from a general population in non-hospital health units were included. Their children were evaluated at birth and in the second or third years of life. Newborns (NB) had their weight percentiles calculated for both curves. Sensitivity, specificity, positive (PPV) and negative predictive value (NPV), and area under the ROC curve (ROC-AUC) for perinatal outcomes and neurodevelopmental delay were calculated using birth weight < 3rd percentile as the cutoff.

RESULTS

 A total of 967 children were evaluated. Gestational age at birth was 39.3 (±3.6) weeks and birth weight was 3,215.0 (±588.0) g. INT and FMF classified 19 (2.4%) and 49 (5.7%) newborns below the 3rd percentile, respectively. The prevalence of preterm birth, tracheal intubation >24 hours in the first three months of life, 5th minute Apgar <7, admission to a neonatal care unit (NICU admission), cesarean section rate, and the neurodevelopmental delay was 9.3%, 3.3%, 1.3%, 5.9%, 38.9%, and 7.3% respectively. In general, the 3rd percentile of both curves showed low sensitivity and PPV and high specificity and NPV. The 3rd percentile of FMF showed superior sensitivity for preterm birth, NICU admission, and cesarean section rate. INT was more specific for all outcomes and presented a higher PPV for the neurodevelopmental delay. However, except for a slight difference in the prediction of preterm birth in favor of INT, the ROC curves showed no differences in the prediction of perinatal and neurodevelopmental outcomes.

CONCLUSION

 Birth weight below the 3rd percentile according to INT or FMF alone was insufficient for a good diagnostic performance of perinatal and neurodevelopmental outcomes. The analyzes performed could not show that one curve is better than the other in our population. INT may have an advantage in resource contingency scenarios as it discriminates fewer NB below the 3rd percentile without increasing adverse outcomes.

[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.

Marital Status, Father Acknowledgement, and Birth Outcomes: Does the Maternal Education Matter?

We evaluated whether the maternal marital status and father acknowledgement (proxy for paternal presence) affect birth weight, and if so, whether the maternal educational attainment modifies this effect. The growing tendency of alternative forms of family structure affects maternal well-being and pregnancy outcome. However, it is not known whether poorer birth outcomes of out-of-wedlock childbearing can be overcome or compensated by maternal education. Using birth registry data, we assessed the impact of maternal civil status and child recognition by the father on birth-weight-for-gestational age (BWGA) z-scores, with respect to maternal education, among Polish mothers (N = 53,528). After standardization, the effect of being unmarried with father acknowledgement (UM-F) vs. married with father acknowledgement (M-F) reduced the BWGA z-score of 0.05 (p < 0.001), irrespective of educational attainment (p for interaction = 0.79). However, education differentiated the effect of father acknowledgement across unmarried mothers. BWGA z-scores were significantly lower among the low-educated unmarried group without father acknowledgment (UM-NF) as compared to UM-F (equaled -0.11, p = 0.01). The same effect among the higher-educated group was non-significant (p = 0.72). Higher maternal education can compensate for the negative effect of a lack of father acknowledgement, but it does not help to overcome the effect of out-of-wedlock stress exposure.

Birth weight for gestational age: standard growth charts for the Polish population

Introduction. Birth weight is one of the most important factors determining neonatal well-being. From an epidemiological viewpoint, a neonatal reference chart provides a picture of the health status of a population. Global customized growth charts seem to be the most practical in multicultural settings, allowing adjustment for ethnicity. However, regional charts might be a valuable contribution to reliable growth assessment. Our study aims to establish a reference tool for growth assessment and visualize the local potential, by creating standard charts based on the data from the tertiary center with the highest number of deliveries per year in Poland. Material and Methods. We retrospectively analysed  31,353 records from the electronic database of singleton births from a five-year period from a tertiary hospital in Poznań, Poland. We excluded pre-term deliveries and high-risk pregnancies basing on well-known factors influencing fetal growth, bringing the number of records to  21,379. The data were processed separately by gender (females n=10,312, 48.2% and males n=11,067, 51.8%). Percentiles were calculated for each week of gestational age. Means and standard deviations were determined. Results. Standard growth charts (including 3rd, 10th, 25th, 50th, 75th, 90th and 97th percentiles) are presented. Descriptive data of population distribution are shown. Conclusions. In conclusion, obtaining standard growth charts for mature newborns has created the opportunity for a more actual and adequate assessment of the Polish neonatal population. It should allow for the implementation of new standards in future research on perinatal care.

Growth Abnormalities as a Risk Factor of Adverse Neonatal Outcome in Hypertensive Pregnancies-A Single-Center Retrospective Cohort Study

(1) Background: Hypertensive disorders of pregnancy (HDP) include gestational hypertension (GH), chronic hypertension (CH), preeclampsia (PE), and preeclampsia superimposed on chronic hypertension (CH with PE). HDP is associated with several short and long-term perinatal and neonatal complications, such as newborn growth restriction and death. This study aimed to establish the association between HDP, newborn growth abnormalities, and neonatal outcome. (2) Methods: This is a single-center retrospective cohort study of 63651 singleton deliveries. (3) Results: Univariate analysis showed a significantly increased risk of intrauterine and neonatal death associated with maternal hypertension and growth disorders. There were differences between growth charts used, with the highest risk of stillbirth for SGA defined by the Intergrowth chart (OR 17.2) and neonatal death for newborn growth restriction (NGR) based on Intergrowth (OR 19.1). Multivariate analysis showed that NGR is a stronger risk factor of neonatal death than SGA only. (4) Conclusions: HDP is significantly associated with growth abnormalities and is an independent risk factor of adverse outcomes. The presence of newborn growth restriction is strongly associated with the risk of neonatal death. The choice of growth chart has a substantial effect on the percentage of diagnosis of SGA and NGR.

Fetal Growth Diagnosis and Management among Perinatal Medical Professionals: A Survey of Practice and Literature Review

INTRODUCTION

This paper aimed to assess the knowledge of healthcare professionals (obstetric and gynecology residents, specialists, and midwives) in the field of perinatal medicine regarding fetal growth diagnosis and management.

METHODS

A questionnaire was created consisting of a set of questions regarding demographic data, methods of growth assessment, and management. It was a handout survey. The results were analyzed with the use of descriptive statistics and χ2 analysis using the program Statistica.

RESULTS

190 medical professionals have participated in the questionnaire. 86.3% of respondents agreed that pregnancy dating should be modified based on first-trimester ultrasound. 90.9% agreed that III trimester ultrasound has a ±15% margin of error. When asked which growth charts are best fit for assessing growth in a studied population, 10.7% marked standard, 37.4% reference, 26.2% customized, and 26.2% did not know the difference between the three choices. 60.3% stated that they use a growth chart to assess growth and qualify fetuses for monitoring. 70.2% used the 10th centile as a cutoff, 20.1% 5th centile, and 9.7% 3rd centile. Only 40.9% would diagnose fetal growth restriction based on fetal weight only. 28.7% using the 10th centile cutoff, 16.1% 5th centile, and 54.0% 3rd centile. Only a quarter of the respondents were able to name the growth chart or tool that they use for assessment. The most common responses were Yudkin, Hadlock, and online calculators of Fetal Medicina Barcelona and the Fetal Medicine Foundation.

DISCUSSION

A lot of confusion is observed primarily in the aspect of cutoff values for identification, subsequent monitoring, and management of fetal growth restriction. There is a need for extensive training and education in this field and uniform national recommendations.

Large-for-gestational-age or macrosomia as a classifier for risk of adverse perinatal outcome: a retrospective cross-sectional study

OBJECTIVE

Small for gestational age (SGA) fetuses and neonates are of great interest, while those who are too big are much less studied. The aim was to analyze the classifiers described by ACOG "Fetal macrosomia" practice bulletin as predictors of adverse perinatal outcomes for overgrown fetuses and their mothers.

MATERIALS

From a database of 53,586 singleton term births, appropriate-for-gestational-age (AGA), large for gestational age (LGA), and macrosomic deliveries were selected. AGA served as a control. The crude and adjusted odds ratios (aORs) were calculated for large-for-gestational-age >90th centile, and macrosomia >4000 g, >4250 g, and >4500 g. Patients with and without diabetes were analyzed separately.

RESULTS

Macrosomia >4000 g performed poorer than other classifiers. LGA performed comparably to other definitions of macrosomia. Diabetes carries a severe risk of complications for overgrown neonates, but those non-diabetic also have increased risk.

CONCLUSIONS

Definition of macrosomia as weight >4000 g should be reconsidered. LGA >90th centile should be used as a definition of fetal overgrowth along with other definitions of macrosomia.