The fetal heart may begin to beat at approximately the 22nd day after fertilization which corresponds to 3 weeks and 1 day after fertilization i.e. 5 weeks 1 day of pregnancy. Between 5 ½ to 6 ½ weeks based on the last menstrual period, a fetal pole or a fetal heartbeat may be detected by vaginal ultrasound.
Angiogenic cell clusters are the building blocks of what will become a fetal heart tube known as the primitive heart tube. The primitive heart tube develops around three to four weeks and goes through an incredible transformation transforming into a four-chamber heart.