In Canada, about 900 babies each year are born very early (<26 weeks of gestation) and have a high chance of dying or having a serious bleed in the brain. Families of these extremely preterm babies consider preventing severe brain bleeding as critical to their child's health and well-being. A medicine called indomethacin, when given intravenously in 3-doses, is known to reduce severe brain bleeding. But use of this drug is variable among clinicians working in the neonatal intensive care unit (NICU) due to (a) its side effects on the gut; (b) possible harm when used with other medications; (c) a notion that despite reducing brain bleeds, the child's long-term brain development is not improved. Emerging evidence suggests that a single low-dose indomethacin regimen may be equally effective in reducing severe brain bleeding as compared to a traditional 3-dose regimen.

The investigators propose a blinded randomized controlled trial, a study design where babies born <26 weeks will be randomly assigned within 12 hours of birth to either a single dose of intravenous indomethacin or similar looking placebo in the form a saline solution. The study will test if a single dose indomethacin regimen is effective in improving survival of these babies without the devastating complication of severe brain bleeding. In this study the care providers and researchers will be unaware as to which baby receives indomethacin and which baby receives placebo to ensure no one's expectations or biases can influence the results.

The investigators will conduct the study in multiple NICUs across Canada, the United States and Australia in 2 phases: First, an internal pilot phase that will enroll 104 babies born <26 weeks or <750 g birth weight over a period of 1 year. If the investigators are successful in achieving their target enrolment in the pilot phase, they will move on to the second phase and continue enrollment up to a total of 500 babies born <26 weeks or <750 g birth weight over a period of 3 years. The total of 500 babies will include the 104 babies enrolled in the first phase of the study. This study will help the investigators determine in the most unbiased way whether a single dose of indomethacin given immediately after birth in the smallest babies born <26 weeks of gestation can safely and effectively reduce severe brain bleeding.

BACKGROUND & IMPORTANCE In Canada, about 900 infants are born extremely preterm at <26 weeks of gestation (GA); nearly four out of 10 of them do not survive or develop severe intraventricular hemorrhage (sIVH). Existing evidence shows that a 3-dose regimen of prophylactic intravenous indomethacin (0.1mg/kg/dose every 24h for 3 doses most commonly used clinically) results in a significant reduction in sIVH, an outcome deemed critical by families. However, use of the conventional 3-dose regimen has declined among clinicians due to perceived adverse effects on the gut, presumed lack of long-term neurodevelopmental benefit and preclusion of other early therapeutic interventions such as ibuprofen or hydrocortisone due to potential increased risk of gut perforation with concomitant use with indomethacin.

Recent pharmacokinetic studies show that indomethacin drug clearance is significantly reduced in infants born ≤26 weeks GA in the first week of life due to their developmental immaturity; and consequently a single 0.1 mg/kg dose likely maintains therapeutic levels for at least 72h - the most critical period of sIVH onset in these smallest infants. However, no RCTs have yet been conducted to establish effectiveness and safety of this single dose regimen in this highest risk population.

GOAL(S) / RESEARCH AIMS Primary goal: To determine the effectiveness and safety of single dose prophylactic indomethacin to prevent morbidity and mortality in extremely preterm infants born <26 weeks GA.

The investigators hypothesize that in preterm infants born <26 weeks GA, when compared to placebo, a single 0.1 mg/kg dose of intravenous indomethacin given prophylactically within the first 12 hours of birth will improve survival without sIVH.

METHODS/APPROACHES/EXPERTISE Study design: Multicenter, blinded, placebo-controlled, individually randomized, Bayesian design RCT Population: Preterm infants born <26 weeks GA and/or <750 g birth weight Intervention: Prophylactic indomethacin: Single-dose intravenous indomethacin (0.1 mg/kg) given within 12 hours of birth. Comparison: Equal volume saline placebo.

Sample size and analysis: The proposed sample size is 500 neonates (250 per arm). The primary analysis will utilize a Bayesian approach using an informative prior that assumes a 5% expected net benefit (in absolute risk difference) with an uncertainty of 5%, with regards to the primary outcome. The trial will be considered successful if it shows that the posterior probability of a positive net benefit is at least 90%.

Setting: Neonatal intensive care units across Canada, the United States and Australia over 3 years. The study will be conducted in 2 phases: (i) an internal pilot phase that will enroll 104 infants born <26 weeks or <750 g birth weight over a period of 1 year; (ii) If the investigators are successful in achieving their target enrolment in the pilot phase, they will move on to the second phase and continue enrollment up to a total of 500 infants born <26 weeks or <750 g birth weight over a period of 3 years. The total of 500 infants will include the 104 infants enrolled in the first phase of the study.

Primary outcome: Survival without sIVH (grades 3 and 4) at hospital discharge Secondary outcomes include in-hospital clinical outcomes; white matter injury on MRI at term corrected age; neurodevelopmental impairment at 24 (±6) months; pharmacokinetic (PK) profile of single-dose indomethacin; total hospital costs and costs per sIVH or death averted.

EXPECTED OUTCOMES This will be the first RCT to explore the effectiveness and safety of single dose prophylactic indomethacin exclusively in infants born <26 weeks GA who are at the highest risk of severe IVH and death. Apart from the primary and secondary clinical outcomes, this trial will describe the PK profile of single dose indomethacin to establish the ideal therapeutic window for sIVH prevention as well as ascertain the value for money of this therapy in preventing death and sIVH in infants born <26 weeks GA.

Inclusion Criteria:

• Extremely preterm infants born <26 completed weeks of GA and/or extremely low BW infants born <750g

Exclusion Criteria:

• antenatal diagnosis of duct dependent CHD
• acute hypoxic respiratory failure [defined as fraction of inspired oxygen (FiO2)>0.60 for ≥2h)
• inhaled nitric oxide (iNO) therapy due to suspected or confirmed acute pulmonary hypertension (PH)
• receipt of prophylactic or therapeutic hydrocortisone
• antenatal diagnosis of renal anomalies
• initial platelet count <50x109/L
• decision to withhold/withdraw life-sustaining treatments](streamdown:incomplete-link)

All of the individual participant data on clinical outcomes collected during the trial will be shared after deidentification.

As soon as possible, wherever legally and ethically possible. In addition, data from the trial will be made available upon reasonable request.

The indomethacin and placebo will be provided to the bedside nurse as per allocation using pre-filled syringes masked with a yellow tape (as reconstituted indomethacin has a slightly yellow tinge). All members of the medical team and outcome assessors will remain blinded to the allocation throughout the trial duration.