a science which study the processes and regulations of development of human fetus. from 1 cell(zygote)to(5-7) x10 cells) oIn general the length of pregnancy is considered to be 280 days or 40 weeks after the onset of the last menstruation, or more accurately, 266 days or 38 weeks after fertilization Onset of Fertilization last M.c 14 days 266 days abor 280 daysFertilization 14 days Onset of last M.C. 266 days 280 days ◆ a science which study the processes and regulations of development of human fetus.(from 1 cell (zygote) to (5-7) x1012 cells) ◆In general the length of pregnancy is considered to be 280 days or 40 weeks after the onset of the last menstruation, or more accurately, 266 days or 38 weeks after fertilization. Labor