Children born preterm are at risk of complications due to immature organ systems. The lungs are normally not ready for gas exchange until the 24th gestational week. Numerous studies have shown the beneficial effect of antenatal steroids on lung maturation. To enhance maturation of the lungs, antenatal steroids are now standard treatment for women at risk of preterm birth prior to 34th gestational week. This has significantly increased the possible for a premature child to survive, and to survive without severe lung disease. However, questions still remains as to ideal dosage, type of steroid or form of administration. The relevant literature is reviewed.
The cellular mechanisms of the beneficial steroid therapy are not completely understood. It is known that steroids increase the production of surfactant. We postulated that they additionally increase apoptosis in the interstitial tissue and thus make gas-exchange easier by reduced distance between alveolar epithelium and septal capillaries. The hypothesis was tested in an experimental pilot study.
A series of chick embryo were treated with either steroids or placebo at various stages of late embryonic life. The number of interstitial lung mesenchymal cells in apoptosis was counted in sections immunostained with apoptosis-markers TUNEL and caspase 3. Only small differences were seen between the steroid group and controls. The apoptotic index alone could thus not alone explain the beneficial effects of steroids in the interstitial tissue. Our revised hypothesis additionally includes increases capillary neovascularisation in the interstitial tissue.