‘Optimal degree’ of catch-up growth defined for SGA babies

By Eleanor McDermid, Senior medwireNews Reporter

A growth trajectory in which small for gestational age (SGA) babies achieve catch-up growth to a defined degree within the first few months of life appears to be best for their subsequent health, say researchers.

Jun Zhang (Shanghai Jiao Tong University School of Medicine, China) and team found excessive catch-up growth to be associated with an increased risk of overweight/obesity and elevated blood pressure. Conversely, no or insufficient catch-up growth was associated with outcomes such as low IQ and growth restriction among infants who were born SGA at term and monitored until the age of 7 years.

“This finding suggests that postnatal growth pattern of term SGA infants, rather than SGA status itself, may be a more important contributor to health outcomes later in life”, the researchers write in The Journal of Pediatrics.

“Therefore, strategies designed to manipulate the biology of fetal growth may be less effective. Rather, those that aim to influence postnatal growth and nutrition and detect postnatal influences on adult health would offer a greater likelihood that practical public health interventions could be devised and investigated in this evolving area.”

The original cohort of term infants with complete data numbered 21,247, of whom 1957 were SGA. The team identified five growth trajectories among these children:

* No catch-up growth (22.4%)

* Initial catch-up growth with regression after 4 months (14.6%)

* Slow catch-up growth (16.8%)

* Appropriate catch-up growth, achieving weight around the 50th percentile (37.3%)

* Excessive catch-up growth, achieving weight around the 90th percentile (8.9%)

Infants with appropriate catch-up growth grew rapidly during the first 4 months, moving from about the 10th to the 30th percentile. Then they had slower catch-up growth over the next few years, reaching percentile 48.9, on average, by the age of 7 years.

These children had similar health outcomes to those born an appropriate weight for their gestational age. By contrast, those with no catch-up growth had an increased risk of infection in infancy, and growth restriction and low IQ at the age of 7 years, with risk increases of 1.2-, 11.2- and 2.1-fold, respectively. Those whose growth regressed after initial catch-up had a 2.2-fold increased risk of growth restriction and those with slow catch-up growth had a 1.6-fold increased risk of low IQ.

At the other end of the spectrum, children with excessive catch-up growth had a 7.5-fold increased risk of overweight/obesity and a 1.7-fold increased risk of elevated blood pressure.

These associations were independent of confounders including gender, race, socioeconomic status, maternal smoking, breast or bottle feeding and parity, and the researchers found similar associations for weight-to-length growth trajectories.

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