Objective: To know the updated outcomes of preterm infants with acute respiratroy failure attributable to presumed pulmonary hypoplasia ( PH) following prolonged maternal mid-trimester preterm premature rupture of membrane ( PPROM). Methods: We retrospectively reviewed the medical records of 76 infants weighing 1,500 g and 23-34 weeks’ gestational age at birth after maternal prolonged (≥ 7 days ) PPROM before 25 weeks of gestation ( PPROM25). We conducted matching (1: 1) of infants unexposed to PPROM (NP, n=76) for each PPROM 25 infants. PPROM25 group was subdivided into infants with acute respiratory failure attributable to pulmonary hypoplasia ( PPH, n=20) and without PH ( PNPH, n=56). Clinical characteristics and major outcomes were compared among these three groups. Risk factors for mortality and morbidities were analyzed using multivariate logistic regression. Results: The survival rate of PPROM25 infants was 81.6% with 87.5% in PNPH, 65% in PPH, and 92.1% in NP respectively. PPH showed significantly higher rate of mortality, periventricular leukomalacia ( PVL) and composite morbidity including mortality, bronchopulmonary dysplasia (BPD), IVH, and PVL than PNPH and NP respectively, while those had no significant difference between PPROM25 and NP. Pulmonary hypoplasia and low birth weight were significant risk factors for composite morbidity, and only pulmonary hypoplasia was significant risk factor for mortality of PPROM25 infants. Conclusion: Although the survival rate of preterm infants after mid-trimester PPROM improved significantly, acute respiratory failure attributable to presumed pulmonary hypoplasia still significantly increased their mortality and morbidities.