Ultrasound examinations during pregnancy are necessary to monitor the growth and development of the fetus and to reduce the birth rate of deformed and defective children. Nowadays, some hospitals’ obstetrics and gynecology departments take a photo album of the fetus through ultrasound during the ultrasound examination of the mother-to-be, which means that the fetus will be photographed in the mother’s belly. Many mothers-to-be want to take pictures of their babies as a souvenir, but they also worry that this will have an impact on the baby’s development. The experts say that it is necessary to conduct ultrasound examinations scientifically and reasonably under the guidance of a doctor, and if the fetus is photographed in the ultrasound, then there will be no effect on the fetus, but if it is necessary to do ultrasound alone to take pictures, and for a longer time, then the mother should choose carefully. There are also many pregnant women who are afraid of the safety of doing ultrasound and have many questions about how to do a reasonable ultrasound, so how many ultrasounds should be done during pregnancy? Ultrasound is usually not needed in early pregnancy (especially before 8 weeks of pregnancy). This is because it is a critical period for the formation of fetal organs and an important stage that can easily lead to fetal malformations. Except for those with vaginal bleeding and abdominal pain (abnormal pregnancies such as ectopic pregnancy, gravida, and indolent miscarriage need to be excluded), patients with pelvic masses or uterine fibroids before pregnancy or early pregnancy, ultrasound is needed to assist in diagnosis and provide a basis for future treatment. If the time of menopause is unclear and it is difficult to correctly estimate the week of pregnancy based on symptoms and signs, it is generally more appropriate to examine the fetus at 10~13 weeks of pregnancy. In the middle and late stages of pregnancy, the organs of the fetus have been formed and ultrasound examination is still relatively safe. Ultrasound should be performed regularly from 20 weeks of pregnancy, but it is best not to do more than the following 3 times during the whole pregnancy: First time: around 20 weeks of pregnancy. Observe the fetal head, spine, heart, lungs, stomach and intestines, both kidneys, bladder, external genitalia and limbs. At this time, the fetus’ limbs are stretched out and it is the best time to check for malformations such as large limbs. The second time: 24~32 weeks of pregnancy. Focus on observing fetal nasolabial region and heart, malformations of nasolabial region and heart can be found. The third time: full-term pregnancy (37~41 weeks of gestation). The fetal position, umbilical cord, amniotic fluid, placenta staging, fetal size estimation, blood flow in the umbilical cord, and intrauterine fetal safety assessment should be emphasized at this time. It provides valuable reference for clinicians to choose the timing and mode of delivery. In addition, fetal echocardiography at 24-28 weeks is necessary for pregnant women with the following risk factors: history of congenital heart disease; maternal diabetes mellitus, connective tissue disease; maternal exposure to specific drugs or infections during pregnancy; maternal alcoholism; advanced maternal age and abnormal maternal history; fetal arrhythmia, fetal edema, chromosomal abnormalities. In general, 3~4 ultrasound examinations are sufficient during pregnancy, but if abnormalities such as abdominal pain, vaginal bleeding, frequent and reduced fetal movement and unclear fetal position occur during pregnancy, ultrasound examination is also required at the discretion of the doctor.