Antenatal corticosteroids for periviable birth.

Antenatal corticosteroids have been proven to accelerate fetal lung development and reduce neonatal morbidity and mortality when given between 28 and 34 weeks of gestation. However, there is only limited research to guide their use in the periviable period (22-26 weeks). Laboratory studies suggest that it is biologically plausible for antenatal steroids to be effective in this gestational period. In addition, cohort studies have demonstrated the efficacy of antenatal corticosteroids in reducing neonatal mortality and IVH. Follow-up studies performed between 18 and 22 months of age also suggest a long-term benefit to antenatal use in this period. Based on this information, antenatal corticosteroids should be used in appropriate patients at high risk for preterm birth at 23-26 weeks of gestation. An advantageous outcome to treatment at 22 weeks is less certain.