Objectives: to compare the intrauterine and postnatal growth of preterm infants according to the Intergrowth-21st and Fenton curves. Methods: study carried out in a maternity hospital, reference in high-risk pregnancy, with preterm infants born in 2018 who were hospitalized in the neonatal units of the institution. Preterm newborns weighed at least twice after birth were included in the sample and those that were syndromic, malformed or presented fluid retention were excluded. Proportions and means were compared using Pearson’s chi-square and Student’s t tests for paired samples, respectively. The McNemar test was used to compare categorical variables and the Kappa test to verify the degree of agreement between birth weight classifications obtained by the curves. Results: one hundred and fifty three infants with a median gestational age of 34.4 weeks were included. The incidences of the categories of nutritional status at birth did not differ between the curves. There was perfect agreement between the curves, except when newborns born under 33 weeks of gestational age were evaluated, in which case the agreement was substantial. About 21% of the babies classified as small for gestational age (SGA) by Intergrowth-21st were adequate for gestational age (AGA) according to Fenton and, on average, 20% of cases that had postnatal growth restriction (PNGR) according to Fenton standards were categorized as adequate weight by Intergrowth-21st. Postnatal weight classifications obtained by the evaluated curves had perfect agreement. Conclusions: the differences in theclassifications found between the charts reveal the importance of choosing the growth curve for monitoring preterm infants since behaviors based on their diagnoses can impact the life of this population.

Background Preterm newborn nutrition affects postnatal skeletal growth and bone mineralization, but studies have not yet fully concluded the relationship between nutrition and osteopenia. This study was intended to investigate the impact of nutritional factors on osteopenia in preterm newborns. Methods This is a case–control study with babies born with gestational age ≤ 32 weeks in a high-risk maternity hospital, between 2018 and 2019. The population consisted of 115 newborns, being 46 cases (40%) and 69 controls (60%). Disease outcome was based on serum alkaline phosphatase levels > 900UL/l and hypophosphatemia < 4 mg/dl. Gestational data at birth and clinical and nutritional follow-up data during 8 weeks postnatally were assessed. Variables were assessed using regressive logistic models. Findings Preterm infants who were fed pasteurized fresh human milk with acidity ≥ 4 ºDornic are 5.36 times more likely to develop osteopenia (p = 0.035). Higher calcium intake, compared to controls, also increased the probability of disease occurrence [OR 1.05 (CI 1.006–1.1); p = 0.025], while the presence of a partner [OR 0.10 (CI 0.02–0.59); p = 0.038] and the shortest time using sedatives [OR 0.89 (CI 0.83–0.98); p = 0.010] were protective factors associated with osteopenia. Extremely low birth weight [OR 5.49 (CI 1.20–25.1); p = 0.028], sepsis [OR 5.71 (CI 1.35–24.2); p = 0.018] and invasive ventilatory support [OR 1.09 (CI 1.03–1.18); p = 0.007] were risk factors. Conclusions Acidity and high calcium intake are the main nutritional factors associated with osteopenia of prematurity. Further studies on the use of human milk with lower acidity, recommendation and nutritional supplementation of calcium should be accomplished to guide prevention strategies in newborns at risk for osteopenia during hospital stay.