What happen this week:
Conception: egg and sperm meet, creating a single cell organism (the zygote). Zygote (a cell resulting from the fusion of two gametes) divides. A two-sided ball is formed. Zygote divides two, three, then four times. The now 16-cell solid ball drops into the uterus. Fluid enters the ball, dividing it again – one part becomes the placenta, the other the baby. The zygote becomes attached to the wall of the uterus. The organism is now an embryo. Rapid growth – amniotic sac, amniotic cavity and yolk sac are developing. The placenta begins to form and blood circulates within it. Chorionic villi, the tissue lining the placenta, begins to develop.