A prospective observational study using de-identified data from the Neonatal Network Research Database (NNRD) supplemented by additional information on dose, method of surfactant administration and dosing frequency to assess whether the dose and method of administration of surfactant given to preterm infants with respiratory distress syndrome (RDS) affects neonatal outcomes.

The rationale for this study is the clinical relevance of understanding whether surfactant dose affects neonatal outcomes in infants with RDS who are treated in the immediate postnatal period.

In a research environment, the dose of surfactant is rigorously controlled, usually administered at a dose of 100mg/kg or 200mg/kg. In clinical practice, clinicians more frequently follow the 'whole vial dosing' approach, where a full vial is given aiming to get as close as possible to the desired dose. Reasons for whole vial use include reduction of waste and administration of surfactant shortly after birth where an infant's weight is unknown. It is unclear whether whole vial dosing leads to under-dosing or over-dosing and whether either situation affects outcomes.

Information regarding the dose of surfactant delivered, and the method of administration, are not currently routinely recorded in the UK.

The primary objective of the study is to compare two dosing groups (100-130 mg/kg and 170-200 mg/kg) in terms of the proportions of infants who require mechanical ventilation within four days of birth.

Inclusion Criteria:

• <37 weeks gestational age Requiring surfactant for Respiratory Distress Syndrome Record of birth weight available Born after study initiation

Exclusion Criteria:

• 37 weeks gestation age or above Parental opt-out

Newborn infants born in neonatal units in the UK

No plan to share IPD