According to the American Pregnancy Association, the purpose of a 7-week ultrasound is to confirm viable pregnancy, confirm heartbeat, measure the crown-rump length or gestational age, confirm molar or ectopic pregnancy, and assess abnormal gestation. During the early stages of pregnancy, a transvaginal scan may be used.
The American Pregnancy Association states that ultrasounds may be performed at any time during the pregnancy. In the case of a healthy pregnancy, an ultrasound is not a required part of prenatal care. Ultrasounds are most often used to detect abnormalities or other conditions related to the pregnancy and are therefore only necessary when there is cause for concern.