Association of furosemide versus chlorothiazide exposures with serum sodium, potassium, and chloride among infants with bronchopulmonary dysplasia.

OBJECTIVES: To examine the association of novel furosemide versus thiazide diuretic exposure with changes in serum sodium, potassium, and chloride levels among infants with grade 2/3 bronchopulmonary dysplasia (BPD). STUDY DESIGN: Retrospective cohort study of infants admitted to a level IV neonatal intensive care unit (NICU) with grade 2/3 BPD. We measured within-subject change in serum sodium, potassium, and chloride before and after diuretic initiation using multivariable regression to adjust for differences in dosing and clinical covariates. RESULTS: We identified 94 infants contributing 137 novel diuretic exposures. No significant difference was noted in the association between chlorothiazide versus furosemide and serum sodium, potassium, or chloride change in multivariable modeling. CONCLUSIONS: Changes in serum electrolytes were similar for chlorothiazide and furosemide, questioning the perception that chlorothiazide leads to less electrolyte derangement among preterm infants with grade 2/3 BPD.

Correction: Xu et al. Use of Optical Redox Imaging to Quantify Alveolar Macrophage Redox State in Infants: Proof of Concept Experiments in a Murine Model and Human Tracheal Aspirates Samples. Antioxidants 2024, 13, 546.

In the original publication [...].

The association of the room air challenge with long-term outcomes in extremely preterm infants.

OBJECTIVE: Evaluate the association between results of the room air (RA) challenge and death, respiratory morbidity, and neurodevelopmental impairment (NDI) at 2 years' corrected age. STUDY DESIGN: Cohort study of infants born <27 weeks' gestational age who underwent a RA challenge to determine BPD diagnosis at 36 weeks postmenstrual age. RESULTS: Of 1022 infants eligible for the RA challenge, 554 underwent testing and 223 passed. Test result was not associated with death or serious respiratory morbidities [adjusted relative risk (aRR) 1.01, 95% confidence interval (CI) 0.65-1.56] or death or moderate/severe NDI (aRR 1.06, 95% CI 0.81-1.39) at 2 years. CONCLUSION: Results of the RA challenge were not associated with differences in respiratory or neurodevelopmental morbidity at 2 years, suggesting the RA challenge does not add prognostic value in contemporary extremely preterm infants. GOV ID: Generic Database: NCT00063063.

Surfactant treatment at birth in a contemporary cohort of preterm infants with bronchopulmonary dysplasia.

OBJECTIVE: Initial surfactant studies demonstrated improvements in survival and need for respiratory support. However, as the use of non-invasive respiratory support has increased the use of surfactant has decreased. We examined in a contemporary cohort of BPD patients if surfactant use was associated with BPD severity. STUDY DESIGN: An observational study using data from the BPD Collaborative Registry. RESULTS: 971 infants with BPD met entry criteria, 864 (89%) had received surfactant in the first 72 h of life (SURF) and the remainder had not (no surfactant). There was an association between SURF and BPD grade, with a greater likelihood of grade 3 BPD in infants who received surfactant in the DR or who had 2 or more doses. CONCLUSIONS: We speculate that the use of surfactant in the DR and use of multiple doses reflect the impact of perinatal factors beyond immaturity alone that increase the risk for grade 3 BPD.

Associations of PM2.5 exposure with emergency department visits and readmissions among preterm infants with bronchopulmonary dysplasia.

OBJECTIVES: To quantify the association of ambient air pollution (particulate matter, PM2.5) exposure with medically attended acute respiratory illness among infants with bronchopulmonary dysplasia (BPD). STUDY DESIGN: Single center, retrospective cohort study of preterm infants with BPD in Metropolitan Philadelphia. Multivariable logistic regression quantified associations of annual mean PM2.5 exposure (per µg/m3) at the census block group level with medically attended acute respiratory illness, defined as emergency department (ED) visits or hospital readmissions within a year after first hospital discharge adjusting for age at neonatal intensive care unit (NICU) discharge, year, sex, race, insurance, BPD severity, and census tract deprivation. As a secondary analysis, we examined whether BPD severity modified the associations. RESULTS: Of the 378 infants included in the analysis, 189 were non-Hispanic Black and 235 were publicly insured. Census block PM2.5 level was not significantly associated with medically attended acute respiratory illnesses, ED visits, or hospital readmissions in the full study cohort. We observed significant effect modification by BPD grade; each 1 µg/m3 higher annual PM2.5 exposure was medically attended acute respiratory illness (adjusted odds ratio [aOR] 1.65, 95% CI: 1.06-2.63) among infants with Grade 1 BPD but not among infants with grade 3 BPD (aOR 0.83, 95% CI: 0.47-1.48) (interaction p = .024). CONCLUSIONS: Cumulative PM2.5 exposure in the year after NICU discharge was not significantly associated with medically attended acute respiratory illness among infants with BPD. However, infants with Grade 1 BPD had significantly higher odds with higher exposures. If replicated, these findings could inform anticipatory guidance for families of these infants to avoid outdoor activities during high pollution days after NICU discharge.

Acetaminophen for Patent Ductus Arteriosus and Risk of Mortality and Pulmonary Morbidity.

OBJECTIVE: Emerging data indicate that acetaminophen may adversely affect lung health. We examined whether acetaminophen compared with cyclooxygenase (COX) inhibitor alone for patent ductus arteriosus (PDA) is associated with mortality or respiratory morbidity in extremely preterm infants. METHODS: This is a retrospective cohort study using data from the National Institute of Child Health and Human Development Neonatal Research Network. Infants were born at 22 to 28 weeks' gestation or weighing 401 to 1000 g between 2016 and 2020 and received acetaminophen, ibuprofen, and/or indomethacin for PDA closure. The primary outcome was death or grade 2 to 3 bronchopulmonary dysplasia (BPD) at 36 weeks' postmenstrual age. Secondary outcomes included predischarge mortality and respiratory morbidities. Risk ratios were adjusted for baseline and early postnatal factors. Additional exploratory analyses were adjusted for later postnatal covariates. RESULTS: Of 1921 infants, 627 (32.6%) received acetaminophen and 1294 (67.3%) received COX inhibitor only. Multidrug therapy (42.9% vs 4.7%) and surgical or catheter PDA closure (26.5% vs 19.9%) were more common among acetaminophen-exposed infants. Death or grade 2 to 3 BPD at 36 weeks' postmenstrual age was similar between infants treated with acetaminophen versus COX inhibitor only (57.1% vs 58.3%; adjusted relative risk [aRR] 0.96, 95% confidence interval [CI] 0.87-1.06). Acetaminophen was associated with increased risk of predischarge mortality (13.3% vs 10.0%) when adjusting for perinatal and early postnatal factors (aRR 1.42, 95% CI 1.02-1.93), but not in exploratory analyses that included later postnatal factors (aRR 1.28, 95% CI 0.91-1.82). CONCLUSIONS: Treatment with acetaminophen versus COX inhibitor alone for PDA was not associated with the composite outcome of death or BPD in extremely preterm infants. Our results support further evaluation of whether acetaminophen for PDA increases mortality.

Prevention of Inflammatory Disorders in the Preterm Neonate: An Update with a Special Focus on Bronchopulmonary Dysplasia.

BACKGROUND: The rates of major neonatal morbidities, such as bronchopulmonary dysplasia, necrotizing enterocolitis, preterm white matter disease, and retinopathy of prematurity, remain high among surviving preterm infants. Exposure to inflammatory stimuli and the subsequent host innate immune response contribute to the risk of developing these complications of prematurity. Notably, the burden of inflammation and associated neonatal morbidity is inversely related to gestational age - leaving primarily but not exclusively the tiniest babies at highest risk. SUMMARY: Avoidance, prevention, and treatment of inflammation to reduce this burden remain a major goal for neonatologists worldwide. In this review, we discuss the link between the host response to inflammatory stimuli and the disease state. We argue that inflammatory exposures play a key role in the pathobiology of preterm birth and that preterm neonates hereafter are highly susceptible to immune stimulation not only from their surrounding environment but also from therapeutic interventions employed in clinical care. Using bronchopulmonary dysplasia as an example, we report clinical studies demonstrating the potential utility of targeting inflammation to prevent this neonatal morbidity. On the contrary, we highlight limitations in our current understanding of how inflammation contributes to disease prevention and treatment. KEY MESSAGE: To be successful in preventing and treating inflammation-driven morbidity in neonatal intensive care, it may be necessary to better identify at-risk patients and pair therapeutic interventions to key pathways and mediators of inflammation-associated neonatal morbidity identified in pre-clinical and translational studies.

Elevated pulmonary capillary wedge pressure, higher blood pressure, and lower cardiac index in infants with bronchopulmonary dysplasia.

BACKGROUND: Left ventricular diastolic dysfunction indicated by elevated pulmonary capillary wedge pressure (ePCWP) may worsen cardiorespiratory status in bronchopulmonary dysplasia (BPD), but the scope of ePCWP by cardiac catheterization is not well described. METHODS: This single-center retrospective cohort study included infants with BPD without congenital heart disease, significant intracardiac shunts, or pulmonary vein stenosis who underwent cardiac catheterization from 2010 to 2021. ePCWP was defined as >10 mmHg. Quantitative measures of ventricular systolic and diastolic function were performed on existing echocardiograms. Patients with and without ePCWP were compared using the Chi-squared or Wilcoxon rank-sum tests. Associations between catheterization hemodynamics and echocardiographic parameters were assessed by simple linear regression. RESULTS: Seventy-one infants (93% Grade 2 or 3 BPD) met inclusion criteria, and 30 (42%) had ePCWP. Patients with ePCWP were older at catheterization (6.7 vs. 4.5 months, p < 0.001), more commonly underwent tracheostomy (66.7% vs. 29.3%, p = 0.003), and had higher mean systemic blood pressure [64.5 (56.0, 75.0) vs. 47.0 (43.0, 55.0) mm Hg, p < 0.001], higher systemic vascular resistance [11.9 (10.4, 15.6) vs. 8.7 (6.7, 11.2) WU*m2, p < 0.001), and lower cardiac index [3.9 (3.8, 4.9) vs. 4.7 (4.0, 6.3) L/min/m2, p = 0.03] at catheterization. Mean pulmonary artery pressure, pulmonary vascular resistance, and mortality were similar between the groups. Echocardiographic indices of left ventricular diastolic dysfunction did not correlate with PCWP. CONCLUSIONS: ePCWP was common in infants with severe BPD who underwent cardiac catheterization in this cohort. The association between ePCWP and higher systemic blood pressure supports further study of afterload reduction in this population.

Use of Optical Redox Imaging to Quantify Alveolar Macrophage Redox State in Infants: Proof of Concept Experiments in a Murine Model and Human Tracheal Aspirates Samples.

Emerging data indicate that lung macrophages (LM) may provide a novel biomarker to classify disease endotypes in bronchopulmonary dysplasia (BPD), a form of infant chronic lung disease, and that augmentation of the LM phenotype may be a potential therapeutic target. To contribute to this area of research, we first used Optical Redox Imaging (ORI) to characterize the responses to H2O2-induced oxidative stress and caffeine treatment in an in vitro model of mouse alveolar macrophages (AM). H2O2 caused a dose-dependent decrease in NADH and an increase in FAD-containing flavoproteins (Fp) and the redox ratio Fp/(NADH + Fp). Caffeine treatment did not affect Fp but significantly decreased NADH with doses of ≥50 µM, and 1000 µM caffeine treatment significantly increased the redox ratio and decreased the baseline level of mitochondrial ROS (reactive oxygen species). However, regardless of whether AM were pretreated with caffeine or not, the mitochondrial ROS levels increased to similar levels after H2O2 challenge. We then investigated the feasibility of utilizing ORI to examine macrophage redox status in tracheal aspirate (TA) samples obtained from premature infants receiving invasive ventilation. We observed significant heterogeneity in NADH, Fp, Fp/(NADH + Fp), and mitochondrial ROS of the TA macrophages. We found a possible positive correlation between gestational age and NADH and a negative correlation between mean airway pressure and NADH that provides hypotheses for future testing. Our study demonstrates that ORI is a feasible technique to characterize macrophage redox state in infant TA samples and supports further use of this method to investigate lung macrophage-mediated disease endotypes in BPD.

Environmental Determinants of Post-Discharge Acute Respiratory Illness among Preterm Infants with Bronchopulmonary Dysplasia.

OBJECTIVE: To analyze the association of components of the Centers for Disease Control and Prevention (CDC) Environmental Justice Index (EJI) with respiratory health outcomes among infants with bronchopulmonary dysplasia (BPD) within one year after discharge from the neonatal intensive care unit. METHODS: This was a retrospective cohort study of a cohort of preterm infants with BPD. Multivariable logistic regression models estimated associations of EJI and its components with medically attended acute respiratory illness, defined as an ED visit or inpatient readmission, within one year of discharge from the neonatal intensive care unit. A mediation analysis was conducted to evaluate how environmental injustice may contribute to racial disparities in acute respiratory illness. RESULTS: Greater EJI was associated with an increased risk of medically attended respiratory illness (per EJI standard deviation increment, aOR 1.38, 95% CI: 1.12-1.69). Of the index's components, the Environmental Burden Module's Air pollution domain had the greatest association (aOR 1.44, 95% CI: 1.44-2.61). With respect to individual indicators within the EJI, Diesel Particulate Matter (DSLPM) and Air Toxic Cancer Risk (ATCR) demonstrated the strongest relationship (aOR 2.06, 95% CI: 1.57-2.71 and aOR 2.10, 95% CI: 1.59-2.78, respectively). Among non-Hispanic Black infants, 63% experienced a medically attended acute respiratory illness as compared to 18% of non-Hispanic White infants. DSLPM mediated 39% of the Black-White disparity in medically attended acute respiratory illness (p = 0.004). CONCLUSIONS: Environmental exposures, particularly air pollution, are associated with post-discharge respiratory health outcomes among preterm infants with BPD after adjusting for clinical, demographic, and social vulnerability risk factors. Certain types of air pollutants, namely, DSLPM, are more greatly associated with acute respiratory illness. Environmental exposures may contribute to racial disparities in medically attended acute respiratory illness among infants with BPD.

Endotracheal Tube Size Adjustments Within Seven Days of Neonatal Intubation.

BACKGROUND AND OBJECTIVES: Neonatal endotracheal tube (ETT) size recommendations are based on limited evidence. We sought to determine data-driven weight-based ETT sizes for infants undergoing tracheal intubation and to compare these with Neonatal Resuscitation Program (NRP) recommendations. METHODS: Retrospective multicenter cohort study from an international airway registry. We evaluated ETT size changes (downsizing to a smaller ETT during the procedure or upsizing to a larger ETT within 7 days) and risk of procedural adverse outcomes associated with first-attempt ETT size selection when stratifying the cohort into 200 g subgroups. RESULTS: Of 7293 intubations assessed, the initial ETT was downsized in 5.0% of encounters and upsized within 7 days in 1.5%. ETT downsizing was most common when NRP-recommended sizes were attempted in the following weight subgroups: 1000 to 1199 g with a 3.0 mm (12.6%) and 2000 to 2199 g with a 3.5 mm (17.1%). For infants in these 2 weight subgroups, selection of ETTs 0.5 mm smaller than NRP recommendations was independently associated with lower odds of adverse outcomes compared with NRP-recommended sizes. Among infants weighing 1000 to 1199 g: any tracheal intubation associated event, 20.8% with 2.5 mm versus 21.9% with 3.0 mm (adjusted OR [aOR] 0.62, 95% confidence interval [CI] 0.41-0.94); severe oxygen desaturation, 35.2% with 2.5 mm vs 52.9% with 3.0 mm (aOR 0.53, 95% CI 0.38-0.75). Among infants weighing 2000 to 2199 g: severe oxygen desaturation, 41% with 3.0 mm versus 56% with 3.5mm (aOR 0.55, 95% CI 0.34-0.89). CONCLUSIONS: For infants weighing 1000 to 1199 g and 2000 to 2199 g, the recommended ETT size was frequently downsized during the procedure, whereas 0.5 mm smaller ETT sizes were associated with fewer adverse events and were rarely upsized.

Towards a harmonized bronchopulmonary dysplasia definition: a study protocol for an international Delphi procedure.

INTRODUCTION: Bronchopulmonary dysplasia (BPD) remains the most common complication of preterm birth with lifelong consequences. Multiple BPD definitions are currently used in daily practice. Uniformity in defining BPD is important for clinical care, research and benchmarking. The aim of this Delphi procedure is to determine what clinicians and researchers consider the key features for defining BPD. With the results of this study, we hope to advance the process of reaching consensus on the diagnosis of BPD. METHODS AND ANALYSIS: A Delphi procedure will be used to establish why, when and how clinicians propose BPD should be diagnosed. This semi-anonymous iterative technique ensures an objective approach towards gaining these insights. An international multidisciplinary panel of clinicians and researchers working with preterm infants and/or patients diagnosed with BPD will participate. Steering committee members will recruit potential participants in their own region or network following eligibility guidelines to complete a first round survey online. This round will collect demographic information and opinions on key features of BPD definitions. Subsequent rounds will provide participants with the results from the previous round, for final acceptance or rejection of key features. Statements will be rated using a 5-point Likert scale. After completing the Delphi procedure, an (online) consensus meeting will be organised to discuss the results. ETHICS AND DISSEMINATION: For this study, ethical approval a waiver has been provided. However, all participants will be asked to provide consent for the use of personal data. After the Delphi procedure is completed, it will be published in a peer-reviewed journal and disseminated at international conferences.

Postnatal Corticosteroids To Prevent Bronchopulmonary Dysplasia.

Bronchopulmonary dysplasia (BPD) is a common, severe chronic respiratory disease that affects very preterm infants. In utero and postnatal exposure to proinflammatory stimuli contribute to the pathophysiology of BPD. Corticosteroids, because of their potent anti-inflammatory properties, may decrease respiratory morbidity and reduce the risk of BPD in very preterm infants. However, these medications can have adverse effects on the developing brain and other organ systems. This review examines current evidence on the risks and benefits of postnatal corticosteroids used to prevent BPD in preterm infants.

Associations of neighborhood social vulnerability with emergency department visits and readmissions among infants with bronchopulmonary dysplasia.

OBJECTIVES: To characterize associations of the CDC Social Vulnerability Index (SVI) with medically attended acute respiratory illness among infants with bronchopulmonary dysplasia (BPD). STUDY DESIGN: Retrospective cohort of 378 preterm infants with BPD from a single center. Multivariable logistic regression quantified associations of SVI with medically attended acute respiratory illness, defined as emergency department (ED) visits or hospital readmissions within a year after first hospital discharge. Mediation analysis quantified the extent to which differences in SVI may explain known Black-White disparities in medically attended acute respiratory illness. RESULTS: SVI was associated with medically attended respiratory illness (per SVI standard deviation increment, aOR 1.44, 95% CI: 1.17-1.78). Adjustment for race and ethnicity attenuated the association (aOR 1.27, 95% CI: 0.97-1.64). SVI significantly mediated 31% of the Black-White disparity in ED visits (p = 0.04). CONCLUSIONS: SVI was associated with, and may partially explain racial disparities in, medically attended acute respiratory illness among infants with BPD.

Acetaminophen for the patent ductus arteriosus: has safety been adequately demonstrated?

Patent ductus arteriosus (PDA) is the most common cardiovascular condition diagnosed in premature infants. Acetaminophen was first proposed as a potential treatment for PDA in 2011. Since that time acetaminophen use among extremely preterm neonates has increased substantially. The limited available data demonstrate that acetaminophen reduces PDA without evident hepatotoxicity. These findings have led some to suggest that acetaminophen is a safe and effective therapy for PDA closure. However, the lack of apparent hepatoxicity is predictable. Acetaminophen induced cellular injury is due to CYP2E1 derived metabolites; and hepatocyte CYP2E1 expression is low in the fetal and neonatal period. Here, we review preclinical and clinical data that support the hypothesis that the lung, which expresses high levels of CYP2E1 during fetal and early postnatal development, may be particularly susceptible to acetaminophen induced toxicity. Despite these emerging data, the true potential pulmonary risks and benefits of acetaminophen for PDA closure are largely unknown. The available clinical studies in are marked by significant weakness including low sample sizes and minimal evaluation of extremely preterm infants who are typically at highest risk of pulmonary morbidity. We propose that studies interrogating mechanisms linking developmentally regulated, cell-specific CYP2E1 expression and acetaminophen-induced toxicity as well as robust assessment of pulmonary outcomes in large trials that evaluate the safety and efficacy of acetaminophen in extremely preterm infants are needed.

Assessment of Corticosteroid Therapy and Death or Disability According to Pretreatment Risk of Death or Bronchopulmonary Dysplasia in Extremely Preterm Infants.

Importance: Meta-analyses suggest that corticosteroids may be associated with increased survival without cerebral palsy in infants at high risk of bronchopulmonary dysplasia (BPD) but are associated with adverse neurologic outcomes in low-risk infants. Whether this association exists in contemporary practice is uncertain because most randomized clinical trials administered corticosteroids earlier and at higher doses than currently recommended. Objective: To evaluate whether the pretreatment risk of death or grade 2 or 3 BPD at 36 weeks' postmenstrual age modified the association between postnatal corticosteroid therapy and death or disability at 2 years' corrected age in extremely preterm infants. Design, Setting, and Participants: This cohort study analyzed data on 482 matched pairs of infants from 45 participating US hospitals in the National Institute of Child Health and Human Development Neonatal Research Network Generic Database (GDB). Infants were included in the cohort if they were born at less than 27 weeks' gestation between April 1, 2011, and March 31, 2017; survived the first 7 postnatal days; and had 2-year death or developmental follow-up data collected between January 2013 and December 2019. Corticosteroid-treated infants were propensity score matched with untreated controls. Data were analyzed from September 1, 2019, to November 30, 2022. Exposure: Systemic corticosteroid therapy to prevent BPD that was initiated between day 8 and day 42 after birth. Main Outcomes and Measures: The primary outcome was death or moderate to severe neurodevelopmental impairment at 2 years' corrected age. The secondary outcome was death or moderate to severe cerebral palsy at 2 years' corrected age. Results: A total of 482 matched pairs of infants (mean [SD] gestational age, 24.1 [1.1] weeks]; 270 males [56.0%]) were included from 656 corticosteroid-treated infants and 2796 potential controls. Most treated infants (363 [75.3%]) received dexamethasone. The risk of death or disability associated with corticosteroid therapy was inversely associated with the estimated pretreatment probability of death or grade 2 or 3 BPD. The risk difference for death or neurodevelopmental impairment associated with corticosteroids decreased by 2.7% (95% CI, 1.9%-3.5%) for each 10% increase in the pretreatment risk of death or grade 2 or 3 BPD. This risk transitioned from estimated net harm to benefit when the pretreatment risk of death or grade 2 or 3 BPD exceeded 53% (95% CI, 44%-61%). For death or cerebral palsy, the risk difference decreased by 3.6% (95% CI, 2.9%-4.4%) for each 10% increase in the risk of death or grade 2 or 3 BPD and transitioned from estimated net harm to benefit at a pretreatment risk of 40% (95% CI, 33%-46%). Conclusions and Relevance: Results of this study suggested that corticosteroids were associated with a reduced risk of death or disability in infants at moderate to high pretreatment risk of death or grade 2 or 3 BPD but with possible harm in infants at lower risk.

Heterogeneity of Treatment Effects of Hydrocortisone by Risk of Bronchopulmonary Dysplasia or Death Among Extremely Preterm Infants in the National Institute of Child Health and Human Development Neonatal Research Network Trial: A Secondary Analysis of a Randomized Clinical Trial.

Importance: Extremely preterm infants who develop bronchopulmonary dysplasia (BPD) are at a higher risk for adverse pulmonary and neurodevelopmental outcomes. In the National Institute of Child Health and Human Development Neonatal Research Network (NICHD NRN) Hydrocortisone Trial, hydrocortisone neither reduced rates of BPD or death nor increased rates of neurodevelopmental impairment (NDI) or death. Objective: To determine whether estimated risk for grades 2 to 3 BPD or death is associated with the effect of hydrocortisone on the composite outcomes of (1) grades 2 to 3 BPD or death and (2) moderate or severe NDI or death. Design, Setting, and Participants: This secondary post hoc analysis used data from the NICHD NRN Hydrocortisone Trial, which was a double-masked, placebo-controlled, randomized clinical trial conducted in 19 US academic centers. The NICHD HRN Hydrocortisone Trial enrolled infants born at a gestational age of less than 30 weeks who received mechanical ventilation for at least 7 days, including at the time of enrollment, and who were aged 14 to 28 postnatal days. Infants were enrolled between August 22, 2011, and February 4, 2018, with follow-up between 22 and 26 months of corrected age completed on March 29, 2020. Data were analyzed from September 13, 2021, to March 25, 2023. Intervention: Infants were randomized to 10 days of hydrocortisone or placebo treatment. Main Outcomes and Measures: Infants' baseline risk of grades 2 to 3 BPD or death was estimated using the NICHD Neonatal BPD Outcome Estimator. Differences in absolute and relative treatment effects by baseline risk were evaluated using interaction terms in models fitted to the efficacy outcome of grades 2 to 3 BPD or death and the safety outcome of moderate or severe NDI or death by follow-up. Results: Among the 799 infants included in the analysis (421 boys [52.7%]), the mean (SD) gestational age was 24.9 (1.5) weeks, and the mean (SD) birth weight was 715 (167) g. The mean estimated baseline risk for grades 2 to 3 BPD or death was 54% (range, 18%-84%) in the study population. The interaction between treatment group and baseline risk was not statistically significant on a relative or absolute scale for grades 2 to 3 BPD or death; the size of the effect ranged from a relative risk of 1.13 (95% CI, 0.82-1.55) in quartile 1 to 0.94 (95% CI, 0.81-1.09) in quartile 4. Similarly, the interaction between treatment group and baseline risk was not significant on a relative or absolute scale for moderate or severe NDI or death; the size of the effect ranged from a relative risk of 1.04 (95% CI, 0.80-1.36) in quartile 1 to 0.99 (95% CI, 0.80-1.22) in quartile 4. Conclusions and Relevance: In this secondary analysis of a randomized clinical trial, the effect of hydrocortisone vs placebo was not appreciably modified by baseline risk for grades 2 to 3 BPD or death. Trial Registration: ClinicalTrials.gov Identifier: NCT01353313.