Babies who gained weight and head circumference more rapidly during the first month of life scored slightly higher on intelligence tests when they were 6 years old, according to a large new study.
But a baby’s early rate of growth didn’t influence the child’s behavior later in life, according to the study.
“We found that faster growth in the first four weeks following birth
was linked to a small increase in intelligence quotient scores at 6.5
years, but there were no clear effects on children’s behavior,” said the
study’s lead author, Lisa Smithers, a postdoctoral research fellow in
early life nutrition at the University of Adelaide, in Australia.
She added that these findings suggest that “it is important that
parents seek help for any concerns they might have about their baby’s
growth or feeding quite quickly so that any problems can be addressed
“[However], we cannot say that faster growth causes a higher IQ,”
Smithers said. “It is possible that a phenomenon called ‘reverse
causality’ may be at play, for example, if children with lower IQs had
The study results appeared online June 17 and in the July print issue of the journal Pediatrics.
The study included about 17,000 mothers and their babies from
Belarus. Only mothers who delivered a single, healthy baby were included
in the study. In addition, the babies were all born at or after 37
weeks of gestation.
Researchers measured the babies’ weights and head circumferences over
the first four weeks of life. Intelligence was measured using several
IQ scales that were combined to yield a full-scale IQ score at 6.5
years. The full-scale IQ scores can range from 50 to 150, Smithers said,
and the average score is 100. To assess behavior, parents and teachers
completed behavior questionnaires.
Babies with the highest growth in weight and head circumference
scored 1.5 points higher on the IQ scale compared to babies with the
lowest growth. The researchers found no statistically significant
differences in children’s later behavior based on early growth.
“Our study involved thousands of healthy babies, so our findings
reflect a wide range of growth patterns that might be expected within a
healthy population,” Smithers said.
Researchers accounted for other important factors, such as family income and parental education, in their analysis.
“The size of the effect we found on children’s IQ would not be noticeable to individuals,” Smithers said.
But the results may be important in the bigger picture, a U.S. expert said.
“A 1.5-point difference would be meaningless in an individual child
and that child’s success in life, but on a population level, such a
difference may matter,” said Dr. Lisa Thornton, medical director of
pediatric rehabilitation at LaRabida Children’s Hospital in Chicago.
“It’s clear, though, that brain growth equals [thinking ability]
growth, and it’s interesting to see that really early brain growth
correlates to intelligence at 6 years,” she said. “It shows that it’s
important that early feeding difficulties shouldn’t linger.”
Thornton said women who are having breast-feeding trouble should seek
help sooner rather than later. “Breast milk is God’s perfect food, but
this study suggests that it’s better to get nutrition early,” Thornton
Both Thornton and Smithers said this study’s findings don’t suggest that parents should overfeed their babies.
“Babies should never be forced to eat,” Smithers said. “Babies should
be fed on demand. Overfeeding may raise other problems over the longer
term, as there is some evidence to suggest that more rapid growth in
infancy is linked to poorer health outcomes, such as obesity and high
blood pressure. Our study draws attention to the importance of balance.”
Thornton agreed. “Make sure the baby is getting enough food for
optimal growth, but don’t overfeed to try to make the baby smarter,” she