To explore the characteristics of prenatal ultrasound image of triplet pregnancy complicated by twin reversed arterial perfusion sequence (TRAPS) and improve early diagnosis of this rare fetal malformation.

Compare the ultrasound and pathological findings of 6 cases of triplet pregnancy with TRAPS fetus by prenatal ultrasound diagnosis and postnatal diagnosis from April 2001 to April 2017 in Hubei Maternal and Child Health Hospital, and summarize the characteristics of prenatal ultrasound images of TRAPS fetus.

Sonographic findings of the six triplet pregnancy were as follows: (1) Acardiac fetus: all acardias were absence of heart and beat, with hypogenetic lower limbs, five with skin edema and lymphoedema, five were absence of fetal head while one with stunted head, one with hypogenetic upper limb, four with spin and abdominal cavity, four acardias had single umbilical artery and were supplied by umbilical artery draining towards the fetus, two cases showed no blood flow in umbilical artery and fetal body. (2) Pump fetus: all of the six cases with normal anatomical structure, two showed normal amniotic fluid volume while four showed polyhydramnios, three cases had prenatal cardiac dysfunction (one case survived, two cases of intrauterine demise). (3) The third fetal of the triplets (TRAP co-twin ): during the Prenatal ultrasound follow-up five fetus had normal morphology with normal heart function, one fetal with multiple malformations. Prognosis of the triplet pregnancy: one triplet cesarean delivery two normal boys, five triplets were of poor prognosis (four pump fetus of intrauterine demise, one pump fetal of premature death: one TRAP co-twin of intrauterine demise, two TRAP co-twins of premature death, two TRAP co-twins of induced labor), four acardia twins of intrauterine spontaneous blood blocking, two still birth. Fetal chorionic and amniotic membrane: four cases were dichorionic triamniotic triplet pregnancy, one case was monochorionic triamniotic triplet gestation, one case was monochorionic diamniotic triplet pregnancy. Six cases were confirmed by pathologic anatomy.

Triplet pregnancy complicated by TRAPS is a rare and severe multiple pregnancy complication, with its characteristic acoustic image characteristics, combined with color doppler, prenatal ultrasound has a high diagnostic value.