High Risk Infants
There are many influences that can affect development. These influences are termed risk factors and are often divided into biological risk and environmental risk. However, it is recognized that there is often significant overlap and influence between the two categories. Biological and environmental stresses are interactive and together have an additive effect on developmental outcome. Therefore, infants with multiple risk factors typically have a greater risk of disability than infants with single risk factors.
Biological risk factors tend to be associated with more severe developmental disability, mental retardation, and multiple handicaps. Included in this category are prenatal influences such as chromosomal disorders, congenital infections, congenital malformations (both of the brain or other organs), and intrauterine growth retardation. Maternal substance abuse during the pregnancy is also a significant prenatal, and often ongoing, risk factor. Then there are the perinatal (around birth) influences on development. Infants born prematurely are at increased risk of developmental disability. They are also at risk for chronic lung disease, deafness, and brain hemorrhages, which add to their developmental risk. Infants with severe lung disease or neonatal seizures are at increased risk. Some infants have metabolic or endocrine disorders such as hypothyroidism or phenylketonuria, which place them at increased risk without appropriate intervention. Lastly, acquired infections in infancy, particularly involving the brain, can result in compromised development. Children with developmental delay due to biological risk factors are often diagnosed in infancy.
Compromised developmental outcome is due to both biologic and environmental risk factors. Over time, environmental influences affect the development of biologically at-risk children. The environment has the potential to maximize or minimize early developmental delays. Environmental risk factors are cumulative, with each having a small incremental effect on cognitive abilities. The adverse effects of a poor environment become increasingly more evident from about two years of age onward. This influence is most strongly seen in the areas of verbal and general cognitive development. As children age, the tests used to measure intelligence place more and more emphasis on language, and therefore the environmental influences assume greater importance. The reverse is also true: A good environment can have a temporizing effect on the degree of developmental disability, but it does not determine whether the disability occurred. Environmental influence seems to be minimized when the biologic risk is severe.
Environmental risk factors are legion and varied. First, consider that the environment includes caregiver-child interactions, family resources, physical properties, and organization. Within the area of caregiver-child interaction is parenting ability. Limited parenting ability, whether due to youth, inexperience, mental retardation, illicit drug abuse, or mental illness, is a risk factor for developmental disability. Inadequate supervision can lead to accident and injury. Child neglect or abuse increases the risk of developmental compromise. Additionally, parenting ability can be limited due to physical separation because of divorce or incarceration. Caregiver-child interactions also include disciplinary techniques and the family's beliefs and attitudes. All of these can affect development.
Many children at risk of developmental disability often live in families with limited resources, frequently referred to as low socioeconomic status. Housing, financial statuses, maternal education, availability of medical insurance, and availability of appropriate play materials are all part of family resources. Homelessness, poverty, low maternal education, single parent families, and lack of medical insurance have all been associated with increased risk of developmental compromise. Unavailability of medical insurance usually means that preventative medical care, when most developmental surveillance takes place, and prenatal care are not obtained. Additionally, a family's ability to cope when suffering from stressful life events, such as divorce, loss of a job, or death, depends on their own resources and access to external sources of support.
Additional environmental influences impacting development are the physical properties of the environment, such as personal space, crowding, and excessive noise. The level of organization is also an influence. This includes the predictability, structure, and regularity of the home. Over many years, children who live in poor or disorganized families are at increased risk of slower cognitive development and diminished school performance when compared to their peers from more advantaged families.