The development of any sign of secondary sexual maturation at an age earlier than 2,5 standard deviations less than the expected age of pubertal onset is named by precocious puberty. These ages depend on the location or the country. In North America, 9 years for boys and 8 years for girls. Girls are more common than boys (approximately five times). Seventy percents of cause precocious puberty in girls is idiopathic. These girls are taller than their peers as children but ultimately are shorter as adults owing to the premature fusion of the long bone epiphyses.

The onset of pubertal changes usually happen between 10 and 16 years of age. In the United states, the mean age of menarche is approximately 12,4 years. The pubertal changed is determined primarily by genetic factors, but is also influenced by geographic location, and nutrional status. During this transition, a variety of physical, endocrinologic, and psychologic changes accompany the increasing levels of sex steroids.

Tetralogy of Fallot or TOF is the most common heart defect in children that occur due to abnormal development of the fetal heart during the first 8 week of pregnancy.  TOF is one of hearth lesions in which the primary defect is an anterior deviation of the infundibular septum. The 4 abnormalities of the heart described by Fallot include the following; pulmonary stenosis, ventricular septal defect( VSD ), overriding aorta, right ventricular hypertrophy