Abstract:

Objective This study aims to investigate the dynamic alterations in non-nutritive sucking parameters among extremely preterm infants （gestational age < 32 weeks） from 32 to 35 weeks corrected gestational age （CGA）， and to analyze the associated influencing factors. Methods Extremely preterm infants admitted to the Neonatal Intensive Care Unit of Sichuan Provincial Maternity and Child Health Care Hospital between February 2025 and March 2026， with gestational age less than 32 weeks， were recruited into this study. Non-nutritive sucking parameters were measured at corrected gestational ages of 32， 33， 34， and 35 weeks. A linear mixed model was constructed to estimate the weekly growth rate of each sucking parameter. Each clinical factor and its interaction term with corrected gestational age were incorporated into the model sequentially to analyze the effects of each factor on three outcomes： the overall level of sucking parameters （main effect）， the weekly growth rate （interaction effect）， and the endpoint value at 35 weeks of corrected gestational age. Estimated marginal means （EMMeans） with corrected gestational age fixed at 35 weeks were used to calculate the predicted intergroup differences in endpoint values at 35 weeks of corrected gestational age. Spearman rank correlation analysis was conducted to assess the correlation between sucking parameters and clinical indicators at 35 weeks of corrected gestational age， and binary logistic regression was applied to identify the influencing factors for achieving full oral feeding before 35 weeks of corrected gestational age. Results A total of 68 extremely preterm infants were enrolled in this study. The median birth gestational age was 30.8 （29.5， 31.3） weeks， and the median birth weight was 1 380 （1 146.0， 1 658.8） g. As corrected gestational age increased， peak sucking negative pressure， mean sucking negative pressure， and sucking frequency increased significantly （all P < 0.001）， with weekly increments of 1.715 kPa， 0.558 kPa， and 7.348 sucks/min， respectively. Linear mixed model analysis showed that invasive ventilation lasting ≥ 1 week had a significant moderating effect on the weekly growth rates of all three sucking parameters （all interaction terms P ≤ 0.009）. Intrauterine distress and breastfeeding volume > 50% also significantly modified the developmental trajectories of sucking parameters. Among infants born to mothers with gestational diabetes mellitus （GDM） with breastfeeding volume > 50%， higher endpoint values of sucking parameters were observed at 35 weeks corrected gestational age， with negative interaction effects， presenting a pattern of "higher overall baseline level but slower growth rate". Infants receiving kangaroo mother care （KMC） had higher overall levels of sucking parameters， but their weekly growth rates were lower than those of infants who did not receive KMC. Sex， mode of delivery， hypertensive disorders of pregnancy， small for gestational age （SGA）， bronchopulmonary dysplasia （BPD）， and multiple gestation did not show significant effects in any dimension （all P > 0.05）. Spearman rank correlation analysis indicated that birth weight was significantly positively correlated with sucking parameters （P < 0.05）； while total duration of assisted ventilation， time to achieve full oral feeding， and length of hospital stay were significantly negatively correlated with sucking parameters （P < 0.05）. Multivariate binary logistic regression analysis showed that invasive ventilation lasting ≥ 1 week was an independent risk factor that hindered achieving full oral feeding before 35 weeks corrected gestational age （OR = 0.178）， and breastfeeding volume > 50% was an independent protective promoting factor （OR = 4.352）. Conclusions The sucking function of extremely preterm infants exhibits a consistent increasing trend from 32 to 35 weeks postmenstrual age. Invasive ventilation lasting for ≥ 1 week significantly reduces the weekly growth rate of all three sucking parameters； intrauterine distress and a breastfeeding proportion > 50% also significantly alter the developmental trajectory of sucking parameters. Sucking frequency is negatively correlated with time to achieve full oral feeding and length of hospital stay， and can thus be used as an auxiliary indicator for clinical assessment.

Key words: extremely preterm infants, non-nutritive sucking, negative sucking pressure, corrected gestational age, oral feeding, invasive ventilation