Objectives: Abdominal distention is a common indicator of feeding intolerance in premature newborns. In the absence of a precise definition, abdominal distention and its degree are highly subjective. The aim of this study was to construct references and smoothed percentiles for abdominal circumference (AC) and AC to head circumference (HC) ratio (AC/HC) in infants born between 24 weeks and 34 weeks of gestational age. Methods: ACs and HCs were collected weekly in eutrophic premature infants without congenital abdominal or cerebral malformation. AC and HC charts were modeled using the LMS method, excluding measures associated with abdominal distention at clinical examination or intracranial abnormality at cerebral ultrasounds. Changes in AC and AC/HC over time were studied by repeated-measures analysis using mixed-effects linear models. Results: A total of 1,605 measurements were made in 373 newborns with a mean gestational age of 31 [29-33] weeks and mean birth weight of 1,540 [1,160-1,968] g. Of these measurements, 1,220 were performed in normal conditions. Gestational age, postnatal age, singleton status, and respiratory support were significantly associated with AC and AC/HC. LMS curves were generated according to gestational age groups and postnatal age, with coherent profiles. AC/HC was 0.91 [0.86-0.95] in absence of abdominal distention. It was higher in cases of abdominal distention (0.95 [0.89-1.00], p < 0.001) and necrotizing enterocolitis (0.98 [0.93-1.07], p < 0.001). Conclusions: References constructed for AC and AC/HC might be used to assess feeding tolerance in premature infants. AC/HC was more relevant than AC to rationalize the diagnosis of abdominal distention.

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