English: Developing Human Embryo at 6 weeks of Pregnancy. In this picture the human embryo movement is determined by the flickering heat beat in the center of the picture. This ultrasound is commonly perform early in the pregnancy with in the first 8 weeks of development to date the pregnancy and determine viability. All embryos develop at the same pace up until 10 weeks of pregnancy or 8 weeks of embryonic age, there after during fetal development, the human fetus grows at different pace. There are some fetus hat could grow as fast as three weeks ahead. Fetus of mother who have gestational diabetes in particular, tend to be larger and weight more.