Risk Factors Associated with Postnatal Growth Velocity in Preterm Infants in a Tertiary Hospital in Northeast Mexico

Background: Suboptimal growth velocity (GV)-weight < 15 g/kg/day, head circumference (HC) < 0.9 cm/week, and length < 1 cm/week-are related to neurodevelopmental problems. Comorbidities such as sepsis, patent ductus arteriosus, bronchopulmonary dysplasia, hemodynamic instability with use of inotropes, and necrotizing enterocolitis, among others, have been related to suboptimal GV. Therefore, this study aimed to evaluate GV in preterm newborns in the Neonatal Intensive Care Unit of a tertiary-level hospital in Mexico in the first 28 days of life and determine the main factors related to suboptimal GV. Methods: This was an observational, descriptive, retrospective, and longitudinal study. Thirty-one PNBs admitted to the NICU from March 2021 to February 2023 were included. Descriptive statistics were used for neonatal characteristics and factors. They were classified into group 1 (GV < 15 g/kg/day) and group 2 (>15 g/kg/day) and compared with Fisher's exact test. Multivariate linear regression analysis was performed for factors related to suboptimal GV. Results: Among 31 preterm infants (mean GA 30 ± 3 weeks; birth weight 1241 ± 377 g), the mean growth velocity (GV) at 28 days was 16.5 ± 10 g/kg/day for weight (optimal), while length (0.7 ± 0.4 cm/week) and head circumference (0.41 ± 0.28 cm/week) remained suboptimal. Overall, 42% showed GV < 15 g/kg/day, and 58% achieved optimal GV. Multivariate analysis revealed that apnea of prematurity (β = -9.8; p = 0.023) and birth weight < 1000 g (β = -6.3; p = 0.026) were negatively associated with GV, whereas mixed feeding (breast milk + formula) had a positive effect (β = +6.3; p = 0.008). Conclusions: The 31 PNBs studied had a mean GV of optimal weight, and a mean GV of length and HC suboptimal to that suggested by the guidelines. The degree of low birth weight (LBW) and apnea of prematurity had a negative relationship with GV, while the type of feeding showed a positive relationship (p = 0.026, 0.023, and 0.008, respectively).