when does a baby's heart start beating

A baby's heart starts beating very early in pregnancy—typically around 21 to 22 days after fertilization, which corresponds to about the fifth week of pregnancy. At this stage, the heart is still in early development, made up of tubes beginning to contract. This early cardiac activity can sometimes be detected by ultrasound around 5 to 6 weeks of pregnancy, often via a vaginal ultrasound. The heart continues to develop and become more complex over the following weeks, with the heartbeat usually visible on ultrasound by 6 to 7 weeks of pregnancy and more fully formed by week 10.