The average baby weighs 8 pounds. Any baby born less than 5 pounds and 8 ounces is considered low birth weight. Low birth weight is associated with various health complications such as poor growth, increased susceptibility to infection, and a higher risk of developing neurological problems.
The two main causes of low birth weight include preterm birth and intrauterine growth restriction. Risk factors for low birth weight include poor maternal health, toxin exposure, nutrient deficiency, preexisting chronic or autoimmune disease, and low socioeconomic status. According to the CDC, mothers without a college education are 29% more likely to have underweight babies.
One study found that low birth weight was associated with irregular brain structure development and smaller total brain volume. The finding indicates that birthweight can have a profound influence on health outcomes later in life. Another study found that 5% of babies born weighing less than 4.7 pounds developed autism, while 11% of babies born weighing less than 3.5 pounds developed autism. The researchers believe that the risk for autism increases with decreasing birth weight.