Abstract
BackgroundPreterm infants are a group at high risk of having experienced placental insufficiency. It is unclear which growth charts perform best in identifying infants at increased risk of stillbirth and other adverse perinatal outcomes. We compared 2 birthweight charts (population centiles and INTERGROWTH-21st birthweight centiles) and 3 fetal growth charts (INTERGROWTH-21st fetal growth charts, World Health Organization fetal growth charts, and Gestation Related Optimal Weight [GROW] customised growth charts) to identify which chart performed best in identifying infants at increased risk of adverse perinatal outcome in a preterm population.Methods and findingsWe conducted a retrospective cohort study of all preterm infants born at 24.0 to 36.9 weeks gestation in Victoria, Australia, from 2005 to 2015 (28,968 records available for analysis). All above growth charts were applied to the population. Proportions classified as <5th centile and <10th centile by each chart were compared, as were proportions of stillborn infants considered small for gestational age (SGA, <10th centile) by each chart. We then compared the relative performance of non-overlapping SGA cohorts by each chart to our low-risk reference population (infants born appropriate size for gestational age [>10th and <90th centile] by all intrauterine charts [AGAall]) for the following perinatal outcomes: stillbirth, perinatal mortality (stillbirth or neonatal death), Apgar <4 or <7 at 5 minutes, neonatal intensive care unit admissions, suspicion of poor fetal growth leading to expedited delivery, and cesarean section. All intrauterine charts classified a greater proportion of infants as <5th or <10th centile than birthweight charts. The magnitude of the difference between birthweight and fetal charts was greater at more preterm gestations. Of the fetal charts, GROW customised charts classified the greatest number of infants as SGA (22.3%) and the greatest number of stillborn infants as SGA (57%). INTERGROWTH classified almost no additional infants as SGA that were not already considered SGA on GROW or WHO charts; however, those infants classified as SGA by INTERGROWTH had the greatest risk of both stillbirth and total perinatal mortality. GROW customised charts classified a larger proportion of infants as SGA, and these infants were still at increased risk of mortality and adverse perinatal outcomes compared to the AGAall population. Consistent with similar studies in this field, our study was limited in comparing growth charts by the degree of overlap, with many infants classified as SGA by multiple charts. We attempted to overcome this by examining and comparing sub-populations classified as SGA by only 1 growth chart.ConclusionsIn this study, fetal charts classified greater proportions of preterm and stillborn infants as SGA, which more accurately reflected true fetal growth restriction. Of the intrauterine charts, INTERGROWTH classified the smallest number of preterm infants as SGA, although it identified a particularly high-risk cohort, and GROW customised charts classified the greatest number at increased risk of perinatal mortality.
Highlights
Being born small for gestational age (SGA) is associated with greater risk of perinatal death, neonatal morbidity, adverse neurodevelopmental outcomes, and poor long-term adult health [1,2,3]
We compared the relative performance of non-overlapping SGA cohorts by each chart to our low-risk reference population for the following perinatal outcomes: stillbirth, perinatal mortality, Apgar
INTERGROWTH classified the smallest number of preterm infants as SGA, it identified a high-risk cohort, and Gestation Related Optimal Weight (GROW) customised charts classified the greatest number at increased risk of perinatal mortality
Summary
Being born small for gestational age (SGA) is associated with greater risk of perinatal death, neonatal morbidity, adverse neurodevelopmental outcomes, and poor long-term adult health [1,2,3]. In which the majority of neonates are born healthy and appropriate size for gestational age (AGA), a preterm population contains a higher proportion of truly growth-restricted infants This is thought to be due both to placental insufficiency triggering labour in some cases of spontaneous preterm birth [11,12] and to an increase in iatrogenic delivery because of prenatally identified fetal growth restriction (FGR) or preeclampsia [12]. It has been demonstrated that preterm newborns have significantly lower birthweights than would be expected from the estimated weights of fetuses that remain in utero and proceed to term [13], population birthweight centiles are commonly used, both clinically and in research, to define the SGA preterm infant This approach runs the risk of systematically underestimating the occurrence of SGA and under-diagnosing placental insufficiency causing pathological growth restriction in the preterm population. We compared 2 birthweight charts (population centiles and INTERGROWTH-21st birthweight centiles) and 3 fetal growth charts (INTERGROWTH-21st fetal growth charts, World Health Organization fetal growth charts, and Gestation Related Optimal Weight [GROW] customised growth charts) to identify which chart performed best in identifying infants at increased risk of adverse perinatal outcome in a preterm population
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