New York - Smaller babies face a tougher life than normal weight infants and don't fare as well at school, at work or with their health, according to a US study.
Researchers funded by the National Institute on Aging in the United States found that weighing less than 2,4kg at birth had significant and lasting effects which they said proved a link between birth weight, adult health and socio-economic success.
Being born under this weight increased the probability of dropping out of high school by one third, reduced yearly earnings by about 15 percent, and burdened people in their 30s and 40s with the health of someone who is 12 years older.
"Not only does birth weight have large and lasting effects across the life course but its effects become larger later in life," the study authors report.
The authors, economists Rucker Johnson from the University of California and Robert Schoeni from the University of Michigan, analysed more than 35 years of data on more than 12 000 people to see how well-being and disadvantage are transmitted across generations within families.
The study found that compared to their normal birth weight siblings, low birth weight children were 30 percent less likely to be in excellent or very good health in childhood and scored significantly lower on reading and math achievement tests.
The probability of being in fair or poor health as an adult increased by over 70 percent among those with low birth weights and they were nearly twice as likely as normal birth weight siblings to have health problems by age 37 to 52.
The earnings penalty for low birth weights also increased with age. These subjects had 10 percent lower hourly wages from ages 18 to 26 rising to 22 percent between ages 37 to 52.
Schoeni and Johnson said the poor economic status of parents at the time of pregnancy led to worse birth outcomes for their children.
"These negative birth outcomes have harmful effects on the children's cognitive development, health, and human capital accumulation, and also health and economic status in adulthood," they wrote.
"These effects then get passed on to the subsequent generation when the children, who are now adults, have their own children."