The sex of the baby, on the other hand, is determined during fertilization. If an X chromosome is present, the baby is a girl. If a Y chromosome is present, the baby is a boy. Over the course of 20 weeks, a baby's growth should proceed almost seamlessly to form a healthy baby with 20/20 vision and no deformities (Website1). Disruption of fetal exposure to diseases or toxins can lead to birth defects and developmental problems. There is currently no way to repair brain abnormalities from early development. That being said, the mother is one of the main controlling factors due to the risks she decides to take after conception (Website