Objective: To compare maternal, perinatal and long-term outcome of triplet pregnancies managed expectantly with those reduced to twins Design: A retrospective cohort study Setting: Tertiary medical institutions in South Korea Population: We examined short-term and long-term outcomes in 524 triplet pregnancies with three live fetuses before 14 weeks of gestation that were comprised of expectant management(EM) group (n=213) and embryo reduction(ER) group (n=311) from 2006 to 2017. Methods: The two groups were compared for the following outcomes. Main Outcome Measures: 1) the rates of non-viable pregnancy loss before 23 weeks, 2) the rates of preterm birth before 32 weeks of gestation; 3) the number of survival fetuses; and 4) long term neurodevelopmental outcomes. Results: In the EM group, the risk of preterm delivery (<36, <34, <32, and <28 weeks) was higher compared to the ER group. However, the risk of non-viable pregnancy loss was lower [2(0.9%) vs. 20(6.4%), p=0.008] in EM group, and the rate of cases with at least one alive neonate were higher in EM group than ER group [208(97.7%) vs. 287(92.3), p=0.013]. The survival rate until discharge of neonates were also significantly higher in the EM group than the ER group [607(95.0%) vs. 545(87.6), p=0.001]. The risk of developmental delay or cerebral palsy in survived neonates was not different between the two groups of cases. Conclusions: In triplet pregnancies, EM may improve the chance of fetal survival, without any significant differences in developmental delay and cerebral palsy.