ABSTRACT
Few events in mammalian life are as physiologically abrupt as birth. Within seconds the newborn organism must move from a warm, sterile, aqueous environment to a cold, microbe-laden world and an obligate air-breathing state. Successful transition to postnatal life requires prenatal maturation of incipient environmental interfaces such as the lung, skin, gut, and kidney. Functional and structural maturation of these interfaces occurs primarily in the third trimester of pregnancy. Recent evidence indicates these epithelial systems interact within the intrauterine milieu prior to birth, as manifested by changes in amniotic fluid composition and associated structural and biochemical maturation of the epithelial surfaces themselves. The prenatal formation of the epidermal barrier is illustrative of this highly coordinated maturational process leading to the ultimate coupling of the newborn with the postnatal environment.
