Dr. Kellie Murphy is a Maternal Fetal Medicine Specialist. She completed her obstetrical residency program at Albert Einstein College of Medicine in New York City in 1995. She then completed a Maternal-Fetal Medicine fellowship program and a Master of Epidemiology at Columbia Presbyterian Medical Center and School of Public Health in New York. In July of 1998, she joined the department of Obstetrics and Gynecology at the University of Toronto where she is currently an Associate Professor, based out of Mount Sinai Hospital. In addition, she holds a joint appointment with the Institute of Health Policy Management and Evaluation at the University of Toronto. Her primary research interests include prematurity, infectious disease, clinical trials and perinatal epidemiology. Her major professional pursuit has been the study of the effects of antenatal corticosteroid therapy. She designed and implemented the randomized controlled trial, “Multiple courses of Antenatal Corticosteroids for preterm birth Study (MACS)”, funded by the Canadian Institutes of Health Research (CIHR). MACS, which is ongoing, is an international, multi-center, randomized, double-masked clinical trial designed to study the effects of single versus repeated courses of antenatal corticosteroids in women at high risk of preterm birth. The primary outcome was a composite of death and neonatal morbidity. The study recruited 1,858 women through 80 centres from 20 countries around the world. To date, MACS is the largest trial of repeated courses of antenatal corticosteroids. Unlike the prior trials, which suggested that multiple courses of antenatal corticosteroids might be associated with respiratory benefit, MACS definitively demonstrated that repeated courses of antenatal corticosteroids were of no benefit but were significantly associated with a decrease in birth weight, length and head circumference. Subsequent to completion of the primary trial, the team successfully followed this cohort of children, performing follow-up assessments on more than 80% of the cohort at 18 to 24 months and thereafter at five years of age. Dr. Murphy has been invited and continues to lecture at numerous hospitals and scientific conferences, both nationally and internationally, to speak on this important subject, and has been asked to write numerous commentaries, reviews and book chapters on antenatal corticosteroid therapy.