The average length of a newborn baby is 50 centimeters and the average length of a full-term baby is 52 to 54 centimeters. The average length of a newborn baby is 50 centimeters, and usually boys are a little taller. The length of the baby increases by 2 to 4 centimeters from newborn to full-term, which means that the average length of a full-term baby is 52 to 54 centimeters. The main factors affecting the height of babies are the following three points: 1. Nutritional factors: breast milk and milk powder is the most important source of nutrition for babies from birth to one year old, after 6 months, start to add complementary foods, try to take in nutrients in addition to milk, after one year old, start to meal-based, milk becomes supplementary food. In these stages, if the baby favor picky eating, or often sick, dietary nutrient intake is poor, which in turn affects growth and development. 2. Genetic factors: genetics is an important factor affecting the baby’s height, the baby’s growth curve will change according to genetics, if both parents are short, the baby’s height is very high chance of short. 3. Endocrine factors: insufficient secretion of growth hormone or hypothyroidism and other factors, is also the main reason for the baby’s height. In addition, congenital hypothyroidism is also a common cause of IQ retardation.