Acceleration of fetal pulmonary maturity.

Neonatal pulmonary complications attributable to pulmonary immaturity are among the more serious problems attending premature birth. Various observations indicate that glucocorticoids play an important role in the maturation of the fetal lung. Moreover, prenatal maternal administration of corticosteroids has been attended by significantly improved neonatal outcome, including a reduction in the incidences of respiratory distress syndrome (RDS), hyaline membrane disease, and mortality due to intraventricular hemorrhage. Success of treatment is related directly to gestational age, with best results occurring between 30 and 32 weeks' gestation. Significant effects have been reported as early as 28 weeks' and as late as 34 weeks' gestation. The potential maternal and neonatal risks of this therapy have not yet been established. Animal studies using relatively high doses of corticosteroids have resulted in an inhibition of deoxyribonucleic acid (DNA) synthesis and mitosis, leading to profound complications and a rise in fetal mortality. Although follow-up of human subjects has been limited and of short duration, no consistent postnatal effects have been noted. The apparent lifesaving benefits of the treatment, combined with only rare and usually correctable fetal, neonatal, and maternal complications, indicate that the use of corticosteroids for prevention of neonatal respiratory problems may be an important advance in reproductive medicine. It remains to be established, however, what the optimal agent and dose are, and what, if any, are the long-term effects of this therapy.