Comparison of growth curves in very low birth weight preterm infants after hospital discharge.

Monitoring preterm infants' growth is essential to ensure the best prognosis for their growth and development. We aimed to compare growth curves in very low birth weight preterm infants after hospital discharge. In this retrospective longitudinal study, 178 preterm infants' growth was assessed by z-scores for weight for age and length to age and compared between Fenton and Kim and Intergrowth-21st charts from hospital discharge until 50 weeks postnatal, and between Intergrowth-21st and WHO charts, 50 and 64 weeks postnatal. The Kappa test was used to evaluate the agreement of the number of cases classified above or below the -2 Z-score concerning weight-for-age and length-for-age indicators to each proposed curve. Our results found that the agreement between Fenton and Kim and Intergrowth-21st curves was almost perfect for most of the weeks investigated, except 35-38 (k = 0.79) and 47-50 (k = 0.61) weeks postnatal. When evaluating the agreement between WHO and Intergrowth-21st, it was substantial for most of the weeks investigated, except for 55-58 and 69-64 weeks postnatal, in which the agreement was almost perfect (k = 0.84; k = 0.81, respectively). Furthermore, we observed that Fenton and Kim curve identified 8.4% and WHO, 5.8% more cases of preterm infants below -2 z than Intergrowth-21st.Conclusion: Although the agreement of the curves was substantial to almost perfect, the Fenton and Kim and WHO curve seem to identify more cases of preterm infants compared to the Intergrowth-21st, a finding that deserves more in-depth investigation in clinical practice. What is Known: • The adequate interpretation of postnatal growth depends on the standard growth chart. • Studies comparing the classification of anthropometric indicators of preterm infants between growth curves consider only the period from birth to hospital discharge. What is New: • This is the first study that compares the classification of weight-for-age and length-for-age indicators of VLBW preterm infants between Intergrowth-21st and Fenton and Kim curves until 64 weeks postnatal. • Substantial to almost perfect agreement of length-for-age indicator was found between the two growth curves of preterm infants during outpatient follow-up.