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IQ and Birth Size

A growing tribe of researchers hypothesized that birth parameters affect a child’s IQ. Dr. Birit F. P. Broekman, of National University Hospital, Singapore, and colleagues confounded the above claim in the journal "Pediatrics".

Apropos a study conducted on Asian children, babies having healthy growth before birth are likely to have higher IQ scores. This is largely because a healthy growth, in a conducive pre-natal environment, results in higher birth weights, longer birth lengths and large head circumference within the normal range.

Research speaks

To investigate, the researchers studied around 3000 children recruited from three schools in Singapore; almost 2000 children were followed yearly from 1999 onward. Birth measurements were recorded along with childhood IQ between 8 to 12 years of age.

The average IQ score was 114.2, with not much disparity between boys and girls.

The team found that for every 1-centimeter increase in birth length, 1-kilogram increase in birth weight, or 1 centimeter in head circumference, there was a corresponding increase in IQ scores by 0.49, 2.19, and 0.62 points, respectively.

Dr. Broekman reports that "Studies on (very) low birth weight and premature children" showed that IQ is consistently correlated to birth weight." Although in the normal birth size range, this association is less conclusive.

Possible factors leading to lower birth weight babies

In other findings, lower birth weight and lower IQ scores were more likely in children of younger mothers, those with lower educational levels, non-white women and low-income women. Having a father who was a small infant more than triples the chances that a baby will also be born small. Furthermore, if this is the case for the mother as well, the likelihood is over 16 times greater, according to study findings reported by French and US researchers.

IQ Linked To Birth Weight, Even In Healthy Babies

A preliminary study found that a child's weight at birth--even within the normal range--was directly related to IQ at the age of 7 years. As a group, low birth weight babies, or those weighing less than 5.5 pounds, are known to score lower on intelligence tests by the time they join school.

"The main implications are that variations in fetal growth may directly wield its impact on brain development and that the mechanisms may differ from those that seem to explain some of the impact of low birth weight on neurodevelopment," Dr. Thomas D. Matte, the study's lead author proposed. It is proposed that for very low birth weight babies (for instance, those weighing 3.3 pounds or less), other complications or deficits (they are more likely to have vascular problems) hinder the development of the brain.

The surveillance also observed that the relationship between birth weight and later IQ was more applicable for boys than for girls. For every 2.2-pound increase in birth weight, IQ scores rose by an average of 4.6 points among boys and 2.8 points among girls, the investigators published in the August 11th issue of the British Medical Journal.

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