How many ultrasound examinations during pregnancy is good? In the current routine of prenatal ultrasound examination, it is mostly recommended to perform three prenatal ultrasound screenings during pregnancy, which are as follows: 1. Early pregnancy (10-14 weeks of gestation) Screening in early pregnancy is mainly to determine intrauterine pregnancy, multiple pregnancies, assess gestational weeks and posterior nuchal translucency thickness (NT) determination, and to perform prenatal diagnosis of serious malformations such as anencephaly, spina bifida, and single-chamber heart. 2.Mid-trimester (20-26 weeks of gestation) Mid-trimester is the best time to perform fetal malformation screening, which requires systematic standardized cross-sectional examination of all fetal organs and can detect malformations in all parts of the fetus including head and neck, heart and lungs, digestive system, genitourinary system and extremities. 3.Late pregnancy (32 to 36 weeks of gestation) Ultrasound examination is needed again in late pregnancy to monitor intrauterine development and determine fetal maturity while also detecting abnormalities that appear at a later stage of pregnancy, such as polycystic kidney and digestive tract stenosis. In conclusion, with the development of ultrasound technology, the improvement of ultrasound quality and examination level has enabled about 80% of fetal anomalies to be diagnosed prenatally, providing the basis for further reduction of births of disabled children, eugenics and further fetal treatment.