Abstract: The incidence of monozygotic twining （MZT） is increased in those women treated with assisted reproductive technology（ART）. Determining monochorionic or diachorionic twin can be used as a factor for the risk stratification. The perinatal morbidity and mortality of monochorionic diamniotic（MCDA） twin are high. There are several methods of multifetal reduction for MCDA twin with respective merits and demerits. The traditional transvaginal ultrasoundguided puncture and aspiration of embryonic tissue has its demerits. The vessel-occluded techniques have been generally used in the selective reduction for MCDA twin，including the bipolar cord coagulation（BCO） and the radiofrequency ablation（RFA），etc. Premature rupture of membrane（PPROM） and premature delivery are the main complications of selective reduction. However，there is not the standard guideline on the time，method，prognosis and indication of the selective reduction for MCDA twin. It is necessary to do long-term follow-up for those living infants after the multifetal reduction.

Key words: Reproductive techniques, assisted, Twins, monozygotic, Chorion, Pregnancy reduction, multifetal, Prognosis