Low birth weight (LBW) is defined as the birth weight of a live-born infant of less than 5.5 pounds regardless of gestational age – typically caused by a preterm birth or a slow prenatal growth rate.
Risk factors in the mother can contribute to low birth weight: the age and health of the mother, multiple pregnancies, poor nutrition, heart disease, hypertension, drug addiction, alcohol abuse, smoking, and insufficient prenatal care. Environmental risk factors include toxin exposure such as from air pollutions or heavy metals.
LBW is an important predictor of newborn health and survival and is associated with higher risk of infant and childhood mortality. The effects of having a low birth weight are closely associated with fetal and perinatal transience, as both physical growth and cognitive development can be inhibited, or predispose the child to a higher risk of chronic diseases later in life.
Infants who are born severely underweight, as those examined in a University of Oregon study, were found to have smaller brain volume and thus suffered academically.
The research team – led by Caron A.C. Clark, from the Department of Psychology and Child and Family Center at the University of Oregon – analyzed data from magnetic resonance imaging (MRI) of 97 adolescents.
The participants had been part of a low birth weight study of infants born between 1982 and 1986 in a Cleveland neonatal intensive care unit. The longitudinal study had been originally launched in the 1980s with a grant from the National Institute of Child Health and Human Development.
Academic progress of the 201 original participants had been assessed early in their school years, again four years later, and then annually until they were almost 17-years old.
Researchers detected an overall reduced volume of mid-brain structures – regions responsible for connectivity, executive attention, and motor control – especially among those considered with extremely low birth weight (below 1.66 pounds) and very low birth weight (less than 3.31 pounds).
More than half of the babies that weighed less than 1.66 pounds and more than 30 percent of those less than 3.31 pounds at birth later had academic deficits.
Researchers did find that 65.6 percent of very low birth weight and 41.2 percent of extremely preterm children had experienced academic achievement similar to normal weight peers – provoking the need for additional research to in order to determine why some significantly underweight infants suffer developmentally while others do not.
The findings, based a logistic regression analyses of the MRIs done approximately five years ago, were published in the May issue of the journal Neuropsychology.
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