Considering the fact that an unfertilized egg will only live for 12 to 24 hours in a woman' body, the actual act of conception can be viewed as a miracle! Just how does conception occur? Fertilization usually happens in the widest area of the fallopian tube. Once the egg has been penetrated by the sperm, it becomes an ovum. After this, cell division and implantation of the ovum must take place for true conception to occur. Implantation typically occurs a few days after fertiliztion. It is now time for the ovum to develop into an embryo.