The sperm and egg begin to lay on the sixth or seventh day after union. After union, the sperm and egg begin mitosis, and the fertilized egg can divide into two cells in the fallopian tube in about 36 hours, and into 16 cells after 72 hours, and the cell mass can enter the uterine cavity on the fourth day after fertilization and develop in the uterine cavity. By this time, the cells have basically split into 48 cells. After the sperm and egg have united, implantation begins on the sixth or seventh day, and the location of implantation is in the upper 1/3 of the woman’s uterus. If implantation is complete, the embryo is ready to be placed and the placenta will slowly form and begin to nurture the fetus, during which time it is important to rest, not to overwork, and to get adequate nutrition.