Also called the embryonic stage, during the first trimester, cells begin to multiply and form the body. The spinal cord, heart and brain are the first organs to develop. This starts about a week after conception. The placenta alos develops in the embryonic stage and it plays a vital role in pregnancy because it carries nutrients, oxygen and water to your baby. This development takes place about two or three weks after conception. The baby’s body also begins to form. This includes development of facial features, eyes, ears, nasal passage, arms, legs, hair follicles, mouth, taste buds. These developments continue up to week 10. The reproductive organs will have also formed by the end of this stage, but it’s too early to determine gender on an ultrasound.