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Why are babies born before 27 weeks less likely to survive than babies born after 30 weeks?

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The survival of infants born prematurely is heavily dependent on their gestational age and the maturity of their organ systems. Babies born before 27 weeks face significantly higher risks than those born after 30 weeks primarily due to the developmental status of their lungs.1

A critical factor in this survival gap is the presence of surfactant, a substance that prevents the air spaces (alveoli) in the lungs from collapsing. While surfactant may begin to appear in some fetuses at 24 weeks, it is frequently absent in infants born before 30 weeks. This deficiency often leads to respiratory distress syndrome, a major cause of mortality in premature infants.1

Furthermore, infants born at earlier gestational ages are more likely to have underdeveloped organ systems, including an immature gastrointestinal tract that limits their ability to digest and absorb nutrients. They also struggle to maintain body temperature due to a large surface area relative to their size. While advancements in neonatology and the use of intensive care units have improved outcomes, the anatomical and physiological immaturity of infants born before 27 weeks remains a profound challenge to their survival.12