Abstract： Objective To investigate the safety and efficiency of radiofrequency ablation (RFA) in the treatment of complicated multifetal gestations.Methods There were 6 multifetal pregnant women (gestational age ranged from 14+6 to 27 +2 weeks) diagnosed in the Department of Obstetrics,Provincial Hospital Affiliated to Shandong University:two with twin-twin transfusion syndrome (TTTS) stage Ⅳ,one with reversed arterial perfusion sequence,one with dichorionic triamniotic triplets,one with absence of a lower limb,one with severe intrauterine growth restriction.All of them accepted ultrasound-guided selective fetocide by RFA.Results (1) Blood flow of three reduced fetuses stopped completely after one RFA circulation,whereas the other three stopped after two circulations.One reduced fetus stopped heartbeating in 10 minutes after RFA; three reduced fetuses' heartbeats slowed down and stopped completely in 35 minutes after RFA ; and the heartbeats of the other two cases stopped completely within 3 to 7 minutes after RFA.The heartbeats of the reserved fetuses were normal.All of the operations succeeded.(2) The reserved fetuses received a series of ultrasound examinations after the operations.In Case 1,the ascites of the reserved fetus,which was 4.0 cm× 2.3 cm before RFA,disappeared two weeks later; and the umbilical artery systolic/diastolic (S/D) ratio,which was 3.35 before the operation,decreased to 2.70 six weeks later.Amniotic fluid depth decreased from 44.6 cm to normal two weeks after RFA.The reserved fetus received brain MRI three weeks after RFA and no abnormality was detected.In Case 2,the increased heart size (cardiothoracic ratio ＞ 0.35) of the reserved fetus recovered to normal size ten days after the operation ; and the umbilical artery S/D decreased from 4.69 to 3.39 seven days after the operation.Reserved fetuses of the other three cases were normal on ultrasound and MRI after the operations.In Case 6,the ascites of the reserved fetus,which was 2.3 cm × 1.5 cm before RFA,disappeared sixteen days after the operation.The brain MRI suggested normal three weeks after the procedure.Amniotic fluid depth reduced from 11.0 cm to normal two weeks after the operation.(3) Three women delivered normal premature babies,and the other three got healthy mature infants.At present,all children are still in follow-up,and their physical examinations suggest normal.Conclusions RFA is a safe,efficient,minimal invasive treatment,which provides a new choice for fetocide,especially for complicated monochorionic multifetal gestations.Fetocide by RFA can effectively improve the life quality of the reserved fetuses.