Bronchopulmonary dysplasia (BPD) is one of the most common complications of prematurity, occurring in 30% of very low birth weight infants. The benefits of dietary intake of polyunsaturated fatty acids ω-3 (PUFA ω-3) during pregnancy or the perinatal period have been reported. The aim of this study was to assess the effects of maternal PUFA ω-3 supplementation on lung injuries in newborn rats exposed to prolonged hyperoxia. Pregnant female Wistar rats (n = 14) were fed a control diet (n = 2), a PUFA ω-6 diet (n = 6), or a PUFA ω-3 diet (n = 6), starting with the 14th gestation day. At Day 1, female and newborn rats (10 per female) were exposed to hyperoxia (O₂, n = 70) or to the ambient air (Air, n = 70). Six groups of newborns rats were obtained: PUFA ω-6/O₂ (n = 30), PUFA ω-6/air (n = 30), PUFA ω-3/O₂ (n = 30), PUFA ω-3/air (n = 30), control/O₂ (n = 10), and control/air (n = 10). After 10 days, lungs were removed for analysis of alveolarization and pulmonary vascular development. Survival rate was 100%. Hyperoxia reduced alveolarization and increased pulmonary vascular wall thickness in both control (n = 20) and PUFA ω-6 groups (n = 60). Maternal PUFA ω-3 supplementation prevented the decrease in alveolarization caused by hyperoxia (n = 30) compared to PUFA ω-6/O₂ (n = 30) or to the control/O₂ (n = 10), but did not significantly increase the thickness of the lung vascular wall. Therefore, maternal PUFA ω-3 supplementation may protect newborn rats from lung injuries induced by hyperoxia. In clinical settings, maternal PUFA ω-3 supplementation during pregnancy and during lactation may prevent BPD development after premature birth. Full article