To assess clinical value of ultrasound in the management of monochorionic twin (MCT) pregnancies.

A total of 153 MCT pregnancies diagnosed by ultrasound at The First Affiliated Hospital of Anhui Medical University from February 2018 to March 2021 were selected for retrospective analysis, all of which were followed until the end of pregnancies. Fetuses in 65 cases were found to have ultrasonic abnormalities during the pregnancy (abnormal group), and the remaining 88 cases were included in a normal group. The diagnosis of MCTs was made on the basis of early ultrasound findings and confirmed at delivery. Fetal ultrasound biometry measurements and growth parameters were used to monitor the fetus every two weeks or even once a week if complications arose from the first trimester to third trimester. Fetal ultrasound screening for anomalies was performed at gestational weeks 20-24.

In the abnormal group, 13 cases had embryo arrest or reduction in the first trimester and the live birth rate was 31%. There were four abortions in the second trimester. Twin-twin transfusion syndrome (TTTS) was diagnosed in 10 cases (20 fetuses) (4 in stage Ⅰ, 2 in stage Ⅱ, 1 in stage Ⅲ, and 3 in stage Ⅴ); there were 10 neonates alive, and the live birth rate was 50%. Twin anaemia polycytosis sequence (TAPS) was diagnosed in three cases (6 fetuses) and one case was complicated with TTTS; four neonates survived and the live birth rate was 67%. There were three cases (6 fetuses) with twin reversed arterial perfusion sequence (TRAPS); two neonates survived and the live birth rate was 29%. There were 14 cases of selective intrauterine growth restriction (sIUGR) (28 fetuses) (6 cases of type Ⅰ, 2 cases of type Ⅱ, and 6 cases of type Ⅲ); 23 neonates survived, and the live birth rate was 82%. There were 18 cases (36 fetuses) with structural malformations in one of the twins; 21 neonates survived and the live birth rate was 58%. There were two cases of conjoined twins (4 fetuses) and none survived. The live birth rate of MCTs in the abnormal group (49%, 64/130) was significantly lower than that in the normal group (100%, 176/176; P<0.001).

The complication rate and fetal loss rate of MCTs are high. Prenatal ultrasound can detect and manage all kinds of abnormal conditions that may occur during pregnancy in time. Due to the limitations of the clinical examination of twins, prenatal ultrasound, as a screening and monitoring method of MCT, provides an important reference for the clinical decision and prenatal consultation during pregnancy.