Lung ultrasound immediately after birth to describe normal neonatal transition: an observational study.

Objective: Lung ultrasound (LUS) has shown promise as a diagnostic tool for the evaluation of the newborn with respiratory distress. No study has described LUS during 'normal' transition. Our goal was to characterise the appearance of serial LUS in healthy newborns from the first minutes after birth until airway liquid clearance is achieved.

Study Design: Prospective observational study.

Setting: Single-centre tertiary perinatal centre in Australia.

Patients: Of 115 infants born at ≥35 weeks gestational age, mean (SD) gestational age of 38 weeks±11 days, mean birth weight of 3380±555 g, 51 were delivered vaginally, 14 via caesarean section (CS) after labour and 50 infants via elective CS.

Interventions: We obtained serial LUS videos via the right and left axillae at 1-10 min, 11-20 min and 1, 2, 4 and 24 hours after birth.

Main Outcome Measures: LUS videos were graded for aeration and liquid clearance according to a previously validated system.

Results: We analysed 1168 LUS video recordings. As assessed by LUS, lung aeration and airway liquid clearance occurred quickly. All infants had an established pleural line at the first examination (median=2 (1-4) min). Only 14% of infants had substantial liquid retention at 10 min after birth. 49%, 78% and 100% of infants had completed airway liquid clearance at 2, 4 and 24 hours, respectively.

Conclusions: In healthy transitioning newborn infants, lung aeration and partial liquid clearance are achieved on the first minutes after birth with complete liquid clearance typically achieved within the first 4 hours of birth.

Trial Registration Number: ANZCT 12615000380594.