Antenatal corticosteroid therapy and risk of osteoporosis

To assess the risk of maternal osteoporosis associated with antenatal corticosteroid administration for neonatal respiratory distress syndrome prophylaxis.

Prospective longitudinal study.

Maternity unit of Chelsea and Westminster Hospital, London.

Fourteen pregnant women who received dexamethasone therapy for fetal lung maturation in anticipation of delivery before 34 completed weeks of gestation.

Blood samples were collected before dexamethasone administration, 24 hours and 48 hours after the course of dexamethasone, and within 24 hours of delivery. Serum levels of carboxy terminal pro-peptide of type I pro-collagen (PICP) were measured to monitor the rate of bone formation, and serum levels of cross-linked carboxy terminal telopeptide (ICTP) were measured as a marker of bone resorption.

Changes in the markers of bone turnover following dexamethasone administration.

Serum PICP levels dropped 24 hours after dexamethasone therapy (P = 0.001), but partially recovered by 48 hours (P = 0.014) to reach higher than pre-therapy levels at delivery (P = 0.044). Although there were no corresponding changes in the serum levels of ICTP after 24 and 48 hours of therapy, levels increased from pretherapy to delivery (P = 0.006).

Antenatal corticosteroid therapy leads to a transient suppression of, followed by an increase in, bone formation without any significant alteration in the pattern of bone resorption expected during pregnancy.