Figure 3.

This graph depicts the typical changes in the embryonic/fetal heart rate in relation to the gestational as well as post-fertilization age as recorded by transvaginal ultrasonographic measurements during the first trimester. There is a rapid and almost linear increase in the embryonic heart rate from the onset of heart beating up to the end of the seventh post-fertilization week (ninth gestational week) followed by a moderate decrease up to the end of the first/beginning of the second trimester. Based on data from [30].