Results:
Study Population : Three hundred seventy-nine neonates born less than 28 weeks gestation were indentified during the 2010-2018 time period for the retrospective review. A sharp decline was detected in the use of intubation and surfactant administration in the delivery room/or at < 24 hrs of age between 2014 and 2015 (Table 1).
Maternal, Infant and Postnatal Characteristics : Table 2 compares maternal and neonatal characteristics between Epoch 1 and Epoch 2. There were significantly fewer mothers with chorioamnionitis, C-sections, multiple gestations, and male infants in Epoch 2 compared to Epoch 1 (Table 2). There were no other differences in gestational age, birth weight, or percentage of out-born neonates between the two epochs. There were no significant differences in rates of PDA, early sepsis, pneumothorax, NEC/SIP, severe IVH, and ROP between the two groups (Table 3). There were more neonates given postnatal steroids in Epoch 2 compared to Epoch 1 (Table 3), but the incidence of postnatal steroid use is low in both Epochs (6% Epoch 1 vs. 17% Epoch 2), with most infants not receiving postnatal steroids in either EPOCH. When postnatal steroids are administered in our center the DART Protocol is followed [19].
BPD Definitions: There were no statistically significant differences in the incidence of death, BPD, or composite outcome of death or BPD between Epochs 1 and 2 regardless of definition utilized (Table 4). Logistic regression model for the composite of BPD and death controlling for potential confounders in Table 2 and 3 showed no significant associations between any of the variables and the outcome of BPD (Table 4). However, BPD incidence varied widely depending on what definition was applied. In Epoch 1, the incidence of BPD was: 1) 32% at 36 weeks PMA; 2) 68% by the NIH severity definition; 3) 16% at 40 week PMA and; 4) 41% using the NRN ventilation definition. This represents a 3-4 fold difference in incidence depending on the applied definition. In Epoch 2, the incidence again ranged from 35%, 58%, 22% and 49%, between the 4 definitions, respectively.
Clinical Factors Impacting BPD Severity: Maternal and neonatal characteristics of infants who developed moderate/severe BPD via the NIH definition in Epochs 1 and 2 were analyzed separately (Tables 5 and 6). Despite significant decreases important co-morbidities such as sepsis and NEC (Table 5) and in early intubation, mechanical ventilation, surfactant administration (Table 6), there were no significant changes in the rates of BPD. Birth weight (Table 5) was higher in Epoch 2 (782 ± 20g) compared to Epoch 1 (752 ± 16g), but the biologic significance of this difference is unclear. Further, all infants in both Epochs received caffeine therapy from birth making our study different than the study by Vliegenthart et al. where differences in delivery room intubation were accompanied by differences in caffeine use and other respiratory stimulants between the Epochs [20].