498: Do antenatal corticosteroids reduce fetal growth or gestational age at birth? A secondary analysis from the multiple courses of antenatal corticosteroids for preterm birth study (MACS)

or gestational age at birth? A secondary analysis from the multiple courses of antenatal corticosteroids for preterm birth study (MACS) Kellie Murphy, Andrew Willan, Mary Hannah, Arne Ohlsson, Edmond Kelly, Stephen Matthews, Saroj Saigal, Elizabeth Asztalos, Sue Ross, Marie-France Delisle, Kofi Amankwah, Patricia Guselle, Amiram Gafni, Shoo Lee, Anthony Armson Mount Sinai Hospital, University of Toronto, Maternal Fetal Medicine, Toronto, ON, Canada, SickKids Research Institute, Child Health Evaluative Sciences, Toronto, ON, Canada, University of Toronto, Department of Obstetrics and Gynecology, Toronto, ON, Canada, University of Toronto, Department of Paediatrics, Toronto, ON, Canada, Paediatrics, Mount Sinai Hospital, Paediatrics, Toronto, ON, Canada, University of Toronto, Physiology, Toronto, ON, Canada, McMaster University, Paediatrics, Hamilton, ON, Canada, Sunnybrook Health Sciences Centre, Paediatrics, Toronto, ON, Canada, Foothills Medical Centre, Obstetrics and Gynecology, Calgary, AB, Canada, Children’s & Women’s Health Centre of British Columbia, Obstetrics and Gynecology, Vancouver, BC, Canada, York Central Hospital, Obstetrics and Gynecology, Richmond Hill, ON, Canada, Sunnybrook Research Institute, Centre for Mother, Infant and Child Research, Toronto, ON, Canada, McMaster University, Clinical Epidemilogy and Biostatistics, Hamilton, ON, Canada, University of Toronto, Pediatrics, Obstetrics and Gynecology and Physiology, Toronto, ON, Canada, IWK Health Centre, Obstetrics and Gynaecology, Halifax, NS, Canada OBJECTIVE: Multiple courses of Antenatal Corticosteroids for preterm birth Study (MACS) was an international multi-centered doubleblind randomized controlled trial of single vs. multiple courses of antenatal corticosteroids (ACS). Infants exposed to ACS experienced similar composite morbidity and mortality as compared to placebo (12.9 % ACS vs. 12.5% placebo) OR 1.04 (CI 0.77-1.39 p 0.83). Infants in the ACS group were smaller. They weighed less (2216 g vs. 2330 g, p 0.0026), were shorter (44.5 cm vs. 45.4 cm, p 0.001) and had a smaller head circumference (31.1 cm vs. 31.7 cm, p 0.001) vs. placebo. The objective of these secondary analyses was to determine the effect of multiple courses of ACS on infant size, controlling for gestational age at birth and other confounders, and to determine if there was a dose response relationship between infant size and number of courses of ACS. STUDY DESIGN: All women (n 1858) and infants (n 2304) enrolled in MACS were included. The gestational age at birth was compared between randomized groups. Multiple linear regression analyses were undertaken to estimate differences (SE) in birth weight, length and head circumference, for the ACS vs. placebo groups, controlling for gestational age at birth and other confounders. RESULTS: Compared to placebo, infants exposed to ACS were born earlier (estimated difference [SE]: 0.43 weeks [0.17], p 0.0098). Controlling for gestational age at birth and other known confounders, multiple courses of ACS were associated with a decrease in birth weight (-33.5 g [SE 16.7] p 0.045), length (-0.3 cm [SE 0.14] p 0.0187) and head circumference (-0.3 cm [SE 0.08] p 0.0003). Lastly, for each additional course of ACS, there was a trend towards an incremental decrease in birth weight, length and head circumference. CONCLUSION: Infants exposed to multiple courses of ACS were born earlier and were smaller. In addition, a dose response was noted between the increasing number of courses of ACS and a decrease in birth weight, length and head circumference. Therefore, administration of multiple courses of ACS, every 14 days, is not recommended. 499 Respiratory outcomes of early term birth Kobina Ghartey, Jaclyn Coletta, Liza Lizarraga, Elizabeth Murphy, Cande V. Ananth, Cynthia Gyamfi Columbia Presbyterian, Maternal Fetal Medicine, New York, NY, Columbia University Medical Center, Obstetrics and Gynecology, Division of Maternal Fetal Medicine, New York, NY, Columbia University Medical Center, Obstetrics and Gynecology, New York, NY, Columbia University Medical Center, Maternal Fetal Medicine, New York, NY, Columbia University Medical Center, OB/GYN, New York, NY OBJECTIVE: Respiratory morbidity at term is thought to decrease as gestational age approaches 39 weeks. However, the risk still persists. The purpose of this study was to evaluate the extent to which respiratory morbidity is higher for neonates delivered at 37-38 weeks gestation, defined as the early term period, in comparison to morbidity at 39 weeks gestation. STUDY DESIGN: We conducted a retrospective cohort study of term deliveries from 370/7 weeks to 396/7 weeks gestation from January to December 2010. Medical records were reviewed to determine baseline characteristics including maternal demographics, admission diagnosis, indication for delivery, mode of delivery, and prior antenatal corticosteroids. Neonatal outcomes were abstracted from infant charts. Our primary outcome was defined as a composite respiratory morbidity comprised of transient tachypnea of the newborn, respiratory distress syndrome, oxygen usage, CPAP, and intubation. RESULTS: Of 2,273 deliveries between 37-39 weeks, 51% (n 1,169) of women delivered in the early term period. There was a significant increase in adverse neonatal respiratory outcomes in those patients delivered in the early term period (Table). There was a significant decrease in the composite respiratory morbidity in those patients delivered at term as compared with the early term period (Figure). CONCLUSION: The two-fold increased risk of respiratory morbidity of infants in the early term period underscores the urgency for limiting non-indicated deliveries to 39 weeks gestation. Poster Session III Doppler Assessment, Fetus, Prematurity www.AJOG.org