An ultrasound scan is typically performed in the early stages of pregnancy when women experience issues such as abdominal pain or vaginal bleeding. However, for women without symptoms of miscarriage or ectopic pregnancy, an ultrasound can confirm that the fetus is located in the womb and that the pregnancy is progressing normally. An ultrasound can detect a pregnancy in the womb 17 days after ovulation, which is approximately 3 days after a missed period in a regular menstrual cycle. Some women may take a pregnancy test before an ultrasound can detect the pregnancy. In these cases, a blood test to measure pregnancy-related hormone levels can help determine the age of the pregnancy and when it can be seen on an ultrasound.

Two weeks after a missed period, early 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 missed period (6 weeks of gestation calculated from the date of the last period in a regular 28-day menstrual cycle), and if the pregnancy is progressing normally, the heartbeat can also be seen. The presence of a normal heartbeat is a very reassuring sign, significantly lowering the risk of miscarriage. From that point on, the fetus grows rapidly, and 3 weeks after the missed period, the head and body are visible. Four weeks after the missed period, several parts of the fetus can be seen, including normal brain structures and limbs.