This week marks the beginning of Roo’s embryonic period. From now until ten weeks, all of her organs will begin to develop and function.


Right now Roo is an embryo consisting of two layers: the epiblast and the hypoblast, from which all his organs and body parts will develop. The primitive placenta is also made up of two layers at this point. Its cells are tunneling into the lining of the uterus, creating spaces for blood to flow into so that the developed placenta can provide nutrients and oxygen when it starts to function at the end of this week. Also present now are the amniotic sac that will house Roo, the amniotic fluid that will cushion her as she grows, and the yolk sac that produces the baby’s red blood cells and helps deliver nutrients to her until the placenta is ready to take over this duty.