Methods	Type of study: randomised trial.
Participants	Location: single centre in USA (Sacred Heart Hospital, University of Florida, Pensacola, Florida). Timeframe: 3-year period ending in December 1999. Eligibility criteria: women at 25-33 weeks’ gestation who remained undelivered 1 week after a single course of antenatal corticosteroids (defined as 2 doses of 12 mg/dose intramuscular betamethasone), given because of increased risk of preterm delivery. Gestational age range: 25-33 weeks. Exclusion criteria: women were excluded if they were insulin-dependent diabetics, had a drug-addiction, or fetus had a known lethal congenital anomaly. Total recruited: 37 women (37 babies). 18 women in the repetitive courses of antenatal corticosteroid group and 19 women in the single course remote group
Interventions	In the repetitive courses of antenatal corticosteroid group: a weekly course of betamethasone (2 doses of 12 mg/dose betamethasone (Celestone Soluspan; Schering Corporation, Kenilworth, New Jersey), intramuscularly, until birth or 34 weeks’ gestation. In the single-course remote group: weekly courses of placebo intramuscularly, until 34 weeks or birth
Outcomes	Primary outcomes: functional residual capacity, respiratory compliance. Secondary outcomes: admission head circumference, surfactant administration, days on oxygen, and mechanical ventilation
Funding Support	American Lung Association.
Notes	Sample-size calculation: yes. Based on 37 women the average functional residual capacity in the single course remote group is not > 12% smaller than the functional residual capacity in the repetitive group (P = 0.05, power 80%)
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Group assignment done through pharmacy using a randomisation table. Stratification: none stated
Allocation concealment (selection bias)	Low risk	Method of treatment allocation: “group assignment done through pharmacy using a randomisation table.” “The study medication was prepared by the pharmacy.” Stratification: none stated.
Blinding (performance bias and detection bias) All outcomes	Low risk	“Investigators and clinical care providers were unaware of the treatment allocation.” Placebo: 25 mg cortisone acetate, an inactive steroid, identical in appearance to the betamethasone used in the repetitive group
Incomplete outcome data (attrition bias) All outcomes	Low risk	Losses to follow-up: none stated. Intention-to-treat analyses: yes
Selective reporting (reporting bias)	Low risk	No obvious risk of selective reporting.
Other bias	Low risk	No other obvious risk of bias detected.