Introduccion: en los ultimos anos se han incrementado las tasas de nacimientos preterminos. Dos tercios son infantes preterminos tardios. Se han descrito diferentes determinantes de su morbilidad y mortalidad neonatal, pero es desconocido el efecto que sobre estas puede tener el uso de tocoliticos al intentar retrasar el parto cuando el feto podria encontrarse en un medioambiente potencialmente hostil. Objetivo: describir las diferencias en los resultados perinatales cuando se utilizan o no tocoliticos durante el trabajo de parto en preterminos tardios. Metodos: estudio descriptivo retrospectivo. Se analizaron expedientes clinicos de gestantes en trabajo de parto en el periodo pretermino tardio entre noviembre de 2009 y junio de 2010 en la E.S.E Clinica Maternidad Rafael Calvo. Se compararon variables sociodemograficas, clinicas, resultados neonatales entre los grupos con el uso o no de tocoliticos. Resultados: de 196 pacientes, 67 fueron seleccionadas, 31(46,2%) recibieron tocoliticos y 36(53,7%) no. La media de edad y de la edad gestacional fueron de 22,3(DE= 5.9) anos y 35,4(DE= 0,72) semanas, respectivamente. Al comparar los grupos (tocolisis o no), hubo diferencia significativa en el intervalo diagnostico–parto (<0,0001). El 61.2% tuvieron parto por via vaginal. El 52.2% fueron de sexo femenino, una media de peso al nacer de 2714 ± 342.8 gramos y de talla de 47.6 ± 2 cms. El APGAR al minuto fue significativamente mucho menor (entre 3 y 7) en el grupo con tocolisis (p=0.0342). Conclusiones: el uso de tocoliticos durante el trabajo de parto en preterminos tardios podria tener un efecto negativo sobre la respuesta adaptativa al nacer. Rev.cienc.biomed. 2011; 2 (2): 226-232 PALABRAS CLAVES Pretermino tardio. Tocolisis. Resultado neonatal. SUMMARY Introduction: Preterm births rates have increased in last years. Late preterm infants represent two thirds. Several newborn-related morbidity and mortality determinants have been described, however their behavior after tocolytics treatment remains unknown under conditions where fetus could be in a potentially hostile environment. Aims: To describe differences in perinatal results when tocolytics drugs are medicated, or when they are not, during late preterm delivery. Methods: Descriptive and retrospective study was carried out between November 2009 and June 2010 in Clinica Maternidad Rafael Calvo. Clinical records from pregnant patients in late preterm delivery were analyzed. Socio-demographic and medical variables, as well as neonatal results were compared to application, or not, of tocolytic therapy. Results : A total of 67 from 196 patients were selected, of them 31(46.2%) were treated with tocolytics while 36(53.7%) were not. Maternal and gestational age averages were 22.3 ±5.9 years old and 35.4 ±0.72 weeks, respectively. When groups were compared (tocolytic therapy or not), there was not significant difference for diagnosis-delivery interval (p<0.0001). 61.2% were normal vaginal deliveries. Females represented 52.2% newborns, average for birth weight was 2 714 ±342.8 grams and for height was 47.6 ±2 centimeters. APGAR score at first minute was significantly lower (between 3-7) in tocolysis therapy group (p=0.0342). Conclusions: Tocolytics treatment during late preterm delivery could have a negative effect on adaptative response at birth. Rev.cienc.biomed. 2011; 2 (2): 226- 232 KEY WORDS Premature Birth. Tocolysis. Apgar Score