To date, various clinical and animal trials have shown that ultrasound is safe for the fetus. Ultrasound in early pregnancy is critical because spontaneous abortion in early pregnancy accounts for about 10-15% of cases. Ultrasound at 7-8 weeks of gestation can clarify whether the embryo is located in the uterus, whether there is a fetal germ and fetal heart, and provide timely diagnosis of ectopic pregnancy, embryonic arrest, gravidity, and other abnormalities; it can also verify the gestational week by the size of the fetal germ, especially important for those pregnant women who have irregular menstruation and cannot remember their last menstruation; in addition, in twin pregnancies only early pregnancy ultrasound can help identify monozygotic or dizygotic twins. All these findings play a crucial role in future pregnancy care and delivery.