Abstract
BackgroundCurrent fetal-infant growth references have an obvious growth disjuncture around 40 week gestation overlapping where the fetal and infant growth references are combined. Graphical smoothening of the disjuncture to connect the matching percentile curves has never been validated. This study was designed to compare weight gain patterns of contemporary preterm infants with a fetal-infant growth reference (derived from a meta-analysis) to validate the previous smoothening assumptions and inform the revision of the Fenton chart.MethodsGrowth and descriptive data of preterm infants (23 to 31 weeks) from birth through 10 weeks post term age were collected in three cities in Canada and the USA between 2001 and 2010 (n = 977). Preterm infants were grouped by gestational age into 23–25, 26–28, and 29–31 weeks. Comparisons were made between the weight data of the preterm cohort and the fetal-infant growth reference.ResultsMedian weight gain curves of the three preterm gestational age groups were almost identical and remained between the 3rd and the 50th percentiles of the fetal-infant-growth-reference from birth through 10 weeks post term. The growth velocity of the preterm infants decreased in a pattern similar to the decreased velocity of the fetus and term infant estimates, from a high of 17–18 g/kg/day between 31–34 weeks to rates of 4–5 g/kg/day by 50 weeks in each gestational age group. The greatest discrepancy in weight gain velocity between the preterm infants and the fetal estimate was between 37 and 40 weeks; preterm infants grew more rapidly than the fetus. The infants in this study regained their birthweight earlier compared to those in the 1999 National Institute of Child Health and Human Development report.ConclusionThe weight gain velocity of preterm infants through the period of growth data disjuncture between 37 and 50 weeks gestation is consistent with and thus validates the smoothening assumptions made between preterm and post-term growth references.
Highlights
Current fetal-infant growth references have an obvious growth disjuncture around 40 week gestation overlapping where the fetal and infant growth references are combined
Despite the approximations used in the current growth curves, it remains unclear how preterm infants truly grow through the disjuncture period
We compared the postnatal weight gain of preterm infants in three North American cities to a fetal-infant growth reference (FIGR), which was generated based on a systematic review of the literature before 40 weeks [19] and the World Health Organization Growth Standard (WHOGS) after 40 weeks [20] of gestation
Summary
Current fetal-infant growth references have an obvious growth disjuncture around 40 week gestation overlapping where the fetal and infant growth references are combined. Because fetal-infant growth charts have incorporated two disparate data sets based on the fetus and the term infant, this creates an obvious disjuncture between the two reference data sets. The Babson & Benda growth chart [17], for example, did not describe the smoothing steps of this disjuncture to link their fetal and term infant data sets. The 2003 Fenton growth chart joined the fetal and infant growth reference data by smoothing this disjuncture around 40 weeks gestational age by using computer-assisted graphical methods [18]. Despite the approximations used in the current growth curves, it remains unclear how preterm infants truly grow through the disjuncture period
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