If a woman’s usual periods are normal, she can have an ultrasound after 40 days of pregnancy. The first ultrasound is recommended, which can give a clearer picture of the location and size of the gestational sac and rule out ectopic pregnancy. Ultrasound in early pregnancy is mainly to see if the size and development of the gestational sac is within the normal range. As the pregnancy time increases, ultrasound will be needed several times, such as at 12 weeks, and twice between 18-26 weeks of pregnancy or 30-32 weeks of pregnancy. Ultrasound is a very common and important examination during pregnancy, which is very helpful to understand the growth and development of the baby, and it has no effect on the fetus, so you can do it without worry.