Many obstetricians treat women in preterm labor with repeated courses of ANCS. However, it is unknown whether additional courses of ANCS are beneficial or potentially deleterious for growth or development of these fetuses. In the North American Thyrotropin Releasing Hormone (TRH) trial, women presenting at< 30 weeks gestation in preterm labor received TRH or placebo in combination with ANCS. All women received one course of ANCS. Subsequent courses were given at the discretion of individual obstetricians. Of 1132 infants delivered in the trial, 616 (55%) received one course, 218 (19%) received two courses, 201 (18%) received 3-5 courses and 76 (7%) received 6-13 courses of ANCS. Adjusting for gestational age, we compared the mortality and respiratory outcomes for infants of 25-32 wk gestation who received one course vs. two or more courses of ANCS (90% power to detect 10% difference in outcomeα = 0.05). Among infants born at 25 to < 28 wk, the incidence of RDS was 85% (194/229) for those who received 1 course of ANCS and 85% (89/105) for those who received 2 or more courses (p = 1.00). The incidence of RDS at 28-32 wk was 51% (92/181) for 1 course and 45% (85/191) for 2 or more courses (p = 0.22). The number of courses of ANCS was not associated with birth weight, the incidence of death, chronic lung disease at 28 days or at 36 weeks post-menstrual age, or with other morbidities of prematurity (PDA, IVH, NEC, ROP). There was no association between TRH and any of these outcomes. We conclude from this retrospective analysis that there is no evidence that multiple courses of ANCS are associated with either additional benefit to respiratory outcomes or deleterious effects on growth, when compared to a single course of ANCS. A prospective randomized trial would be necessary to definitively answer this question.