Neonatal hypoglycaemia and body proportionality in small for gestational age newborns: a retrospective cohort study.

Small for gestational age (SGA) newborns are at risk of developing neonatal hypoglycaemia. SGA newborns comprise a heterogeneous group including both constitutionally small and pathologically growth restricted newborns. The process of fetal growth restriction may result in brain sparing at the expense of the rest of the body, resulting in disproportionally small newborns. The aim of this study was to discover whether body proportionality influences the risk of developing neonatal hypoglycaemia in SGA newborns. A retrospective cohort study was performed in 402 newborns who were SGA without additional risk factors for hypoglycaemia. Body proportionality was classified in two ways: (1) using symmetric (sSGA) or asymmetric (aSGA), defined as head circumference (HC) below or above the 10th percentile, respectively; (2) using cephalization index (HC/birth weight), standardized for gestational age. Hypoglycaemia was observed in 50% of aSGA and 40.9% of sSGA newborns (P-value 0.12). Standardized CI in newborns with hypoglycaemia was higher compared to newborns without hypoglycaemia (median 1.27 (1.21-1.35) versus 1.24 (1.20-1.29); (P 0.002)). Multivariate logistic regression analyses showed both CI and standardized CI to be associated with the occurrence of hypoglycaemia (OR 1.48 (1.24-1.77) and OR 1.44 (1.13-1.83), respectively). The majority of hypoglycaemic events (96.1%) occurred in the first 6 h after birth.   Conclusion: Body proportionality might be of influence, depending on the classification used. Larger prospective studies with a clear consensus definition of body proportionality are needed. What is Known: • Neonatal hypoglycaemia is an important complication in newborns. • Small for gestational age (SGA) newborns are more vulnerable to hypoglycaemia. What is New: • Higher incidence of hypoglycaemia was not observed in asymmetric SGA compared to symmetric SGA, but standardized cephalization index was associated with increased likelihood of hypoglycaemia. • Consensus-based definitions of body proportionality in newborns are needed.

From population reference to national standard: new and improved birthweight charts.

BACKGROUND: Antenatal detection of intrauterine growth restriction remains a major obstetrical challenge, with the majority of cases not detected before birth. In these infants with undetected intrauterine growth restriction, the diagnosis must be made after birth. Clinicians use birthweight charts to identify infants as small-for-gestational-age if their birthweights are below a predefined threshold for gestational age. The choice of birthweight chart strongly affects the classification of small-for-gestational-age infants and has an impact on both research findings and clinical practice. Despite extensive literature on pathological risk factors associated with small-for-gestational-age, controversy exists regarding the exclusion of affected infants from a reference population. OBJECTIVE: This study aims to identify pathological risk factors for abnormal fetal growth, to quantify their effects, and to use these findings to calculate prescriptive birthweight charts for the Dutch population. MATERIALS AND METHODS: We performed a retrospective cross-sectional study, using routinely collected data of 2,712,301 infants born in The Netherlands between 2000 and 2014. Risk factors for abnormal fetal growth were identified and categorized in 7 groups: multiple gestation, hypertensive disorders, diabetes, other pre-existing maternal medical conditions, maternal substance (ab)use, medical conditions related to the pregnancy, and congenital malformations. The effects of these risk factors on mean birthweight were assessed using linear regression. Prescriptive birthweight charts were derived from live-born singleton infants, born to ostensibly healthy mothers after uncomplicated pregnancies and spontaneous onset of labor. The Box-Cox-t distribution was used to model birthweight and to calculate sex-specific percentiles. The new charts were compared to various existing birthweight and fetal-weight charts. RESULTS: We excluded 111,621 infants because of missing data on birthweight, gestational age or sex, stillbirth, or a gestational age not between 23 and 42 weeks. Of the 2,599,640 potentially eligible infants, 969,552 (37.3%) had 1 or more risk factors for abnormal fetal growth and were subsequently excluded. Large absolute differences were observed between the mean birthweights of infants with and without these risk factors, with different patterns for term and preterm infants. The final low-risk population consisted of 1,629,776 live-born singleton infants (50.9% male), from which sex-specific percentiles were calculated. Median and 10th percentiles closely approximated fetal-weight charts but consistently exceeded existing birthweight charts. CONCLUSION: Excluding risk factors that cause lower birthweights results in prescriptive birthweight charts that are more akin to fetal-weight charts, enabling proper discrimination between normal and abnormal birthweight. This proof of concept can be applied to other populations.

Prescriptive birthweight charts can improve the prediction of adverse outcomes in very preterm infants who are small for gestational age.

AIM: We compared three anthropometric charts to determine which provided the best predictions for adverse outcomes in very preterm small for gestational age (SGA) infants to address a lack of consensus on this subject. METHODS: This was a retrospective cohort study of infants born below 32 weeks, who were admitted to two-level three neonatal intensive care units in The Netherlands from 2008 to 2013. The birthweights of 1720 infants were classified as SGA using a conventional, gender-specific birthweight chart, based on births in The Netherlands between 2000 and 2007, a prescriptive, gender-specific birthweight chart, based on the same data but without risk factors for intrauterine growth restriction (IUGR), and a non-gender-specific foetal weight chart derived from American ultrasonographic measurements. RESULTS: The conventional, prescriptive and foetal weight charts classified 126 (7.3%), 494 (28.7%) and 630 (36.6%) infants as SGA. The prescriptive chart, which excluded IUGR, identified 368 SGA infants with significantly increased risks of neonatal mortality and morbidity. The 136 SGA infants just classified by the American foetal weight chart were not at increased risk. CONCLUSION: The prescriptive birthweight chart, which excluded infants with IUGR, was the most effective chart when it came to identifying clinically important risk increases in SGA infants.

Defining small-for-gestational-age: prescriptive versus descriptive birthweight standards.

UNLABELLED: Descriptive population-based birthweight standards possess low sensitivity in detecting infants with growth impairment. A prescriptive birthweight standard based on a 'healthy' subpopulation without risk factors for intrauterine growth restriction might be superior. We created two birthweight standards based on live born, singleton infants with gestational age 24-42 weeks and born in The Netherlands between 2000 and 2007. Inclusion criteria for the prescriptive birthweight standard were restricted to infants without congenital malformations, born to healthy mothers after uncomplicated pregnancies. We defined small-for-gestational-age (SGA) as birthweight <10th percentile and assessed the ability of both standards to predict adverse neonatal outcomes. The prescriptive birthweight standard identified significantly more infants as SGA, up to 38.0 % at 29 weeks gestation. SGA infants classified according to both standards as well as those classified according to the prescriptive birthweight standard only, were at increased risk of both major and minor adverse neonatal outcomes. The prescriptive birthweight standard was both more sensitive and less specific, with a maximum increase in sensitivity predicting bronchopulmonary dysplasia (+42.6 %) and a maximum decrease in specificity predicting intraventricular haemorrhage (-26.9 %) in infants aged 28-31 weeks. CONCLUSION: Prescriptive birthweight standards could improve identification of infants born SGA and at risk of adverse neonatal outcomes. WHAT IS KNOWN: • Descriptive birthweight standards possess low sensitivity in detecting growth restricted infants at risk of adverse neonatal outcomes. • Prescriptive standards could improve identification of very preterm small-for-gestational-age (SGA) infants at risk of intraventricular haemorrhage. What is New: • Prescriptive standards identify more preterm and term SGA infants at risk of major adverse neonatal outcomes. • Late preterm and term SGA infants classified according to the prescriptive standard are at increased risk of minor adverse neonatal outcomes with potentially harmful implications.