52 - Respiratory Morbidities and Feeding Milestones in Late Preterm (34-36 Weeks) Small for Gestational Age (SGA) Infants, and Temporal Changes Over a Five-Year Study Period

Publication Number: 4051.52

Ananya Sharma, University of Calgary, Calgary, AB, Canada; Apple Libradilla, University of Calgary Cumming School of Medicine, Calgary, AB, Canada; Selphee Tang, Alberta Health Services, Calgary, AB, Canada; Anjeline Bukhari, University of Calgary, Edmonton, AB, Canada; Ananya Sharma, University of Calgary, Calgary, AB, Canada; Mahira Hassan, University of Alberta, Edmonton, AB, Canada; Kamran Yusuf, Kamran Yusuf, Department of Pediatrics, University of Calgary, Calgary, AB, Canada; Shabih Hasan, University of Calgary, Calgary, AB, Canada

Background: Late preterm infants (LPIs, 34-36 weeks gestational age (GA)) account for over 75% of preterm births yet they remain understudied. LPIs face significant short- and long-term morbidities and many require admission to neonatal intensive care units, often due to being small for gestational age (SGA, < 10th centile). SGA LPIs may be at greater risks of respiratory insufficiency, delayed feeding and prolonged hospitalization compared with non-SGA LPIs, though existing data are inconclusive.

Objective: To address these gaps, we aimed to investigate: 1) whether SGA LPIs have higher respiratory insufficiency compared with non-SGA LPIs, 2) the differences in respiratory and feeding outcomes and length of stay (LOS) across 34-36, 34-35, and 36-week GA groups and 3) temporal changes in perinatal factors and various outcomes between 2016-2018 and 2019-2021 cohorts.

Design/Methods: We analyzed 829 LPIs (34-36 weeks GA) admitted to Foothills Medical Center in Calgary from April 2016 to March 2021. Infants were grouped by GA (34-36, 34-35, and 36 weeks) according to their growth status (SGA vs. non-SGA). The 34-36-week GA group was also divided into birth cohorts (2016-2018 vs. 2019-2021) to assess temporal trends.

Results: SGA LPIs demonstrated a lower incidence of respiratory distress syndrome (RDS) at 34-36 (p=0.037) and 36 weeks (p=0.014) GA than non-SGA LPIs (Table 1A). Fewer SGA than non-SGA LPIs required any respiratory support (19% vs. 35%, p=0.001) or CPAP (15% vs. 29%, p≤0.001) at 34-36 weeks (Figure 2A). SGA LPIs received mother's own milk (MOM) and/or donor human milk (DHM), while non-SGA LPIs received a mixture of MOM, DHM and formula across GA groups (all p≤0.008; Table 1A). SGA LPIs took longer to achieve gavage-free oral feeds (p≤0.043) and were less likely to be discharged within 0-3 days afterward (p≤0.030; Table 1A). More mothers received ≥2 of antenatal corticosteroids (ACS) doses in the 2016-2018 cohort than in the 2019-2021 cohort (p < 0.001), while the incidence of RDS nearly doubled (7% to 15%, p< 0.001; Figure 2B) as ACS use declined. The 2019-2021 cohort had more mixed feeding and less exclusive formula use (2% vs. 7%; p< 0.001), but feed type and earlier oral feeding did not shorten LOS (13 days in both cohorts, p=0.869; Table 1B).

Conclusion(s): SGA LPIs had decreased respiratory insufficiency but longer LOS due to delayed achievement of oral feeding. Evolving ACS use reflects changing practices and outcomes. These findings suggest that 1) there is a critical need to develop SGA-specific feeding strategies and 2) analyses should account for clinical practice changes in studies spanning over years

Fig 1. Infant Flow Diagram
Of the 984 LPIs assessed for eligibility, 829 LPIs met the inclusion criteria. These infants were then stratified into two cohorts 1) growth-based status (SGA vs. non-SGA) and 2) time-based birth-years (2016-2018 vs 2019-2021) for temporal changes; 116 SGA vs. 713 non-SGA and 467 born on 2016-2018 vs. 362 born on 2019-2021, respectively (Fig 1).

Fig 2. Comparisons of respiratory support among SGA and non-SGA LPIs (2A) and Temporal Trends in Antenatal Corticosteroid (ACS) use and respiratory distress syndrome during two birth cohorts (2016-2018 vs. 2019-2021; 2B).
SGA infants received less respiratory support including any respiratory support (19%) and CPAP (15%) compared to 35% and 29% in non-SGA infants, respectively (p < 0.001; Fig 2A). A decline in ACS use in the later birth cohort (2019-2021 vs. 2016-2018; p<0.001) was accompanied by a 2-fold increase in the incidence of RDS (Fig 2B).

Table 1. Maternal and Infant Characteristics and Feeding Outcomes and Length of Stay (LOS) Among Late Preterm Infants (LPI) by Growth Status (SGA vs non-SGA; Table 1A) and Feeding Outcomes Among LPIs by Birth Cohort (2016-2018 and 2019-2021), including LOS (Table 1B).
Comparisons of maternal and infant Characteristics in all gestational age (GA; 34-36, 34-35, and 36 weeks) LPI groups according to their growth status (SGA vs. non-SGA), and their feeding outcomes, including their LOS (Table 1A). Comparisons of feeding outcomes in 34-36 weeks GA LPIs, including their LOS.