Genetics Play Key Role in Infant Postnatal Weight Gain

Monozygotic twins have lower within-pair daily weight gain differences than dizygotic twins

WEDNESDAY, Jan. 4 (HealthDay News) -- Postnatal weight gain in healthy preterm newborns shows a high level of heritability, according to a study published online Jan. 4 in Pediatrics.

Sonia Brescianini, from the Istituto Superiore di Sanità in Rome, and colleagues compared a very homogenous set of monozygotic and dizygotic twins to estimate the variability of postnatal weight gain due to genes and the environment. Twins with gestational age between 30 and 36 weeks, birth weight between 1,250 and 2,200 g, and length of hospital stay of more than 12 days were included in the analysis. Twin pairs of opposite-gender, and pairs whose birth weight differed by more than 20 percent were not included in the analysis. Daily weight gain from the day of birth to the day of discharge was the main outcome measure (expressed in grams per kilogram per day). Heritability, and the average difference between members of a pair, were computed for the participating twins.

The investigators found that monozygotic twins had lower within-pair differences of the daily weight gain from birth to discharge than dizygotic twins. Two sources of variation explained the total variance of the phenotype under study: additive genetic and unique environment components (87 and 13 percent, respectively).

"The importance of our results lie in the future possibility of identifying subsets of newborns who fail to thrive or will experience an exceedingly fast postnatal weight gain to undertake appropriate measures," the authors write.

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