An ultrasound scan is usually performed at the early stages of pregnancy when women experience problems such as abdominal pain or vaginal bleeding. However, in women with no symptoms of miscarriage or ectopic pregnancy, an ultrasound scanning can confirm that the fetus is located in the womb and pregnancy proceeds normally. An ultrasound scanning can detect pregnancy in the womb 17 days after ovulation. This coincides approximately 3 days after a missed menstruation in a regular menstrual cycle. Some women tend to have a pregnancy test before pregnancy can be detected by ultrasound. In these cases, a blood test to measure pregnancy-related hormone levels helps calculate the age of pregnancy and determine when the pregnancy can be seen through ultrasound.

Two weeks after the lost menstruation, initial pregnancy appears on the ultrasound screen as a small cyst in the intrauterine cavity. The fetus can become visible for the first time 2 weeks after the lost menstruation (6 weeks of gestation calculated from the date of the last menstruation in a regular 28-day menstrual cycle), and if pregnancy is normal, heartbeat can become also visible. The presence of a normal heartbeat is a very reassuring sign and the risk of miscarriage is becoming low. From that day onwards, the fetus grows rapidly and 3 weeks after the lost menstruation, the head and body are visible. Four weeks after the missed menstruation, several parts of the fetus can be seen including normal brain structures and limbs.