The sex of the child is determined at the time of fertilization. If an X chromosome is present the baby is a girl. If a Y chromosome is present the child is a boy. Over the course of 20 weeks the way a child grows must proceed almost seamlessly to form a healthy child with 20/20 vision and no deformities (Website 1). An alteration of the fetus in the form of exposure to diseases or toxins can cause birth defects and developmental problems. There is currently no way to repair brain defects early in development. That said, the mother is one of the main controlling factors due to the risks she decides to take after the moment of conception (Website