Pudgy babies may be adorable, but being overweight may delay a baby’s ability to roll over, crawl, or conquer other important physical skills, researchers report.

Meghan Slining, a doctoral student in nutrition epidemiology at the University of North Carolina at Chapel Hill, and colleagues evaluated 215 infants at various times up to 18 months.

Of the 152 infants found to be overweight during any of these evaluations, 20 percent - 31 infants - had delayed motor skills, Slining said in an email to Reuters Health.

During these observations Slining’s team also found 75 babies with high average measures of belly, upper-arm, and upper-back skin fat. Of these, 23 percent - 17 infants - had delayed motor skills, Slining added.

Over all observations, motor skill delays such as an inability to sit steadily for 30 seconds were about twice as likely in overweight and overly pudgy infants than in those with “normal” weight and fat.

The group’s report in the Journal of Pediatrics is the first to “suggest overweight infants and those with excessive body fat may be at greater risk for delayed motor development than infants without extra weight and fat,” she said.

During home visits with the low-income African-American mothers and babies, the researchers documented each infant’s ability to perform 14 to 21 different age-appropriate skills. At each visit they also measured pudginess and weight for length of the infants.

Initially, 62 babies were overweight by U.S. Centers for Disease Control weight-for-length standards for 3-month-old infants. At 6 months 30 were overweight, and by 18 months 14 remained so.

Twenty of the 3-month-olds had higher skin fat averages than the rest of the study group at that age. By 18 months, 12 remained overly pudgy compared with the others.

Generally, 3-month-olds balance their head, sit with support, and roll over, and 6-month-olds sit alone and show signs of crawling. But 6-month-olds with low motor skills might not sit steadily for 30 seconds without support or roll from their backs to their stomachs, Slining said.

Eighteen-month-olds with low motor skills might not have enough balance to walk backwards or sideways, or stand on one foot for two seconds, she noted. Normally, walking skills develop between 9 and 12 months, and 18-month-olds walk backwards and up stairs.

It is important for parents to provide a safe space where infants can and are encouraged to explore, but overweight infants may limit age-appropriate exploration beyond their arm’s reach, Slining and colleagues surmise.

Still, without examining other groups of infants for months and years, researchers won’t know whether excessive weight or body fat causes delayed motor skills in older children, they note.

SOURCE: The Journal of Pediatrics, published online March 15, 2010.