Low birth weight in infants can be caused by premature birth or interuterine growth restriction. IUGR is a term used to describe an infant that is small for gestational age. Premature birth and IUGR can occur as a result of many different pregnancy complications that include an inefficient placenta, infection, multiple gestation, congenital abnormalities, hypertension, drug abuse and poor nutrition. The effect that low birth weight has on an infant varies greatly depending on its cause and severity.
Hypoglycemia
Hypoglycemia, which is low blood sugar, often occurs due to either an insufficient amount of glucose stores in the body or immature organs. Adequate glucose is essential for normal brain functioning. Prolonged hypoglycemia can subsequently lead to brain damage, seizures, coma and death. These infants will require IV therapy or strictly scheduled feeding with frequent glucose monitoring until they are able to efficiently maintain their own glucose levels.
Hypoxia
Hypoxia is a life-threatening condition resulting from a lack of oxygen in the body. In low-birth-weight infants, hypoxia most often occurs due to immature lungs. Prolonged hypoxia can lead to brain damage, organ failure and death. These infants require supplemental oxygen or assisted breathing. The type of treatment will depend upon the severity and cause of the hypoxia. Infants may require treatment from only a few minutes in mild cases to years in severe cases.
Feeding Issues
Infants need to master the coordination of sucking, swallowing and breathing to eat effectively. Low-birth-weight infants may be poor feeders due to lack of this coordination, poor muscle tone or low energy stores. Another complication is feeding intolerance, or an inability to digest the breast milk or formula. These infants may require intravenous nutrition and/or gavage tube feedings until they are able to eat unassisted. Special formulas that are more easily digested can be used.
Cold Stress
Low-birth-weight infants lack the body fat that is needed to maintain their body temperature. Immature infants will lack temperature regulation by the hypothalamus. Cold stress results from a prolonged low body temperature leading to use of available fat in an attempt to maintain body heat. Complications include weight loss, hypoglycemia and respiratory distress. These infants will have their temperatures maintained by an incubator or radiant warmer until they are able to self-regulate.
Developmental Delays
The severity of impairment depends on the severity and cause of the low birth weight. Studies have shown that infants with very low and moderately low birth weights have the highest risk of cognitive impairment and behavioral problems. However, infants who are small for gestational age at full term may be more likely to develop psychological impairment. Physically these children may remain below average weight throughout infancy and may reach developmental milestones later than expected.
References
- MedlinePlus: Intrauterine Growth Restriction
- Lucile Packard Children's Hospital at Stanford: Hypoglycemia in the Newborn
- Birth Weight Effects on Children's Mental, Motor, and Physical Development
- "The British Journal of Psychiatry"; Birth Weight and Psychological Distress at Age 45-51 Years; Nicola J. WIles, et al.; 2005
