When it comes to babies, there's a wide range of what is considered normal. Growth charts and developmental milestones don't tell the entire picture, but can give a general idea of whether an infant is developing normally. There are many things that can affect the development of a baby beyond just normal variations, some of which the baby is born with and others that result from environmental exposures or circumstances.
Nutrition
What a baby eats can affect his development by altering his biology. Malnutrition can significantly disrupt a baby's mental and physical growth and the effects can be permanent even if the child starts to eat better. All babies should be consuming either breast milk or formula exclusively at least through age four to six months; this should be the primary source of food for an infant at least through his first birthday. Breastfed babies may become deficient in certain nutrients, such as vitamin D or iron, if the mother has insufficient intake of these. Vitamin D deficiencies can result in rickets, which hinders the growth of the bones. Low iron intake can result in slower overall growth of an infant and delay his mental development, since his tissues and brain may not be getting enough oxygen from the blood.
Disabilities and Birth Defects
Disabilities have a strong effect on the development of a baby. Babies with genetic defects such as Down syndrome or cystic fibrosis can have delayed development in physical, mental and social areas. Disabilities may be obvious at birth, or may not become apparent until a delay in development is noticed by parents or doctors.
Prematurity
Babies who are born prematurely generally grow and meet developmental milestones more slowly than infants with a gestational age of over 38 weeks. These babies begin life smaller and less developed than normal, and may have difficulty with problems such as immature lungs. However, according to the American Academy of Family Physicians, many premature babies catch up developmentally to other babies by two years of age.
Diseases
Infections and internal diseases, such as allergies, can cause developmental delays in infants. Urinary tract infections, gastroesophogeal reflux disease, diarrhea, respiratory illnesses and parasitic infections can have an effect on development, since they prevent the baby's body from appropriately breaking down the nutrients from food.
Social Factors
For a baby to develop properly, she should have regular interaction with parents and caregivers. Babies who are neglected exhibit a failure to thrive and experience developmental delays. Development is affected not only by physical neglect, such as not feeding a baby often enough, but also by social, mental and emotional neglect. Infants need regular loving touch, attention to their needs and emotional interaction such as being smiled at or talked to.
