Usually, the most dangerous monochorionic twin amniotic twins are in the first trimester of pregnancy. Monochorionic twin amniotic twins are formed by the division of a fertilized egg on days 4-8 after fertilization and are a common type of complicated twin fetus. The first trimester is an important period for fetal organogenesis, and monochorionic bimacental twins are prone to complications such as twin transfusion syndrome, twin selective growth restriction, and twin absent heart sequence syndrome during this period, with a complication rate of 25-30%. Therefore, it is important to monitor pregnant women with single chorionic twin amniotic twin pregnancies and to perform screening tests early in pregnancy. In case of severe amniotic fluid abnormalities (too much or too little) during pregnancy, it is necessary to consider the combination of twin fetus transfusion syndrome; if the fetuses are of different sizes, it is necessary to consider the combination of twin fetuses with selective growth restriction; if there is no heart on one side of the fetus or no skull, it is necessary to consider the combination of twin fetuses with no heart sequence syndrome. In addition, it is recommended that pregnant women with single chorionic twin sheep and twin fetuses need to ensure adequate nutrition during pregnancy, eat foods rich in protein, iron and folic acid, and maintain moderate exercise to prevent anemia and hyperemesis.