A fetus's heart begins to beat very early in pregnancy, typically around 5 to 6 weeks gestation. At about 5 weeks, cardiac tissue starts contracting, and a heartbeat may be detected via vaginal ultrasound. By 6 weeks, the heart's basic tube has looped, and the heartbeat is usually visible. Though it may sometimes be detectable a bit later, by 6 to 7 weeks, ultrasound can generally confirm fetal cardiac activity. The heartbeat is not fully developed until around 10 weeks, but the early pulsations mark an important milestone in fetal development.