For pregnant women with menopause of more than 30 days, the first ultrasound examination is recommended at 35-50 days of menopause to determine if the pregnancy is intrauterine, to exclude ectopic pregnancy, to detect and confirm the diagnosis of chorionic and amniotic multiple pregnancies, and to diagnose double chorionic gestation when the “λ” sign is observed. In the case of a twin chorionic pregnancy, the diagnosis of a single chorionic twin pregnancy can be made when the “λ” sign is observed, and when the “T” sign is observed. The use of color Doppler ultrasound technology allows the observation of fetal heartbeat and fetal movement, identification of viable embryos, early detection of serious malformations, measurement of head and hip length, estimation of gestational weeks, and calculation and correction of the due date. Fetal nuchal translucency (NT) thickness measurement is performed between 11 weeks and 13 weeks 6 days of gestation, combined with maternal serological and biochemical measurements to estimate the risk rate of chromosomal abnormalities. At the same time, fetal echocardiography may be performed to observe the fetal heart structure to detect severe structural anomalies. Trans-thorax may show normal fetal four-chamber heart, heart orientation, size, and position of the cardiac axis. Ultrasonography for detailed fetal systemic anomaly screening (4-dimensional ultrasound) is performed at 18-24 weeks of gestation to observe chromosomal abnormality markers, apply ultrasound to project gestational age, and reduce the rate of diagnosis of overdue pregnancy and preterm delivery. Fetal growth assessment is performed around 32 weeks of gestation to detect intrauterine growth retardation in time to observe the presence of delayed fetal anomalies. about 50% of fetuses with intrauterine growth retardation show growth restriction after 32 weeks on ultrasound and 27% have chronic intrauterine hypoxia. Placental vascular obstruction affects the exchange of material between mother and baby, and the pulsatility index, which measures the obstruction of the placental vascular bed, is a good indicator of placental function, and its use can significantly improve the prognosis in high-risk pregnancies such as intrauterine growth retardation. Due to the limitations of ultrasound and its susceptibility to other factors, it does not mean that a single ultrasound examination can detect all abnormalities. Any abnormality found or suspected in a single ultrasound examination should be followed up more frequently and other prenatal diagnostic methods should be chosen to clarify the diagnosis according to the specific findings. Ultrasound testing should also be increased as appropriate for those who continue the pregnancy with an abnormal fetal examination or if the mother has obstetric or medical comorbidities.