摘要:Background Radiofrequency ablation (RFA) is considered as an optional treatment method in complicated monochorionic (MC) twin pregnancies. The purpose of this study is to investigate the main factors of fetal death after such treatment procedure. The study also compares the perinatal outcomes among various groups of indication and gestational age (GA) at procedure. Materials and Methods: This prospective cohort study considers 195 cases of MC multiple pregnancies including one twin with twin-twin transfusion syndrome, selective intrauterine growth restriction ,sever anomaly and twin reversed arterial perfusion sequence(TRAP) which underwent selected reduction using RFA from 2016 to 2018 at Yas Hospital, Tehran, Iran. The GA at RFA categorized as 16- 19 6 wks., 20-23 6 wks., and 24-28 wks. The analysis of risk factors of fetal death after RFA is based on multivariable logistic regression model. Results: The result of analysis reveals that the rate of co-twin anemia after RFA in anomaly indication was higher than the other indications significantly (p=0.038) while according to GA categories, it is significantly lower in 20-23 6 weeks. (p=0.016). Three independent significant factors contributing in fetal death after RFA were co-twin anemia after RFA, TRAP and anomaly indications of RFA and GA at RFA, respectively. Conclusion The co-twin anemia after RFA was found the most contributing factor of fetal death. As the results showed that the rate of co-twin anemia after RFA is significantly low in 20-23 6 weeks of GA, such GA is suggested for RFA procedure to reduce the fetal death.