Published on July 11, 2016

Weighing the options for tracking your baby’s sizeWeighing the options for tracking your baby’s size

While adults are generally aware when they may have a few extra pounds to shed, how many know what is a healthy size and weight for their babies?

Does body mass index (BMI) have a place in measuring infants and predicting future obesity?

Possibly, says a first-of-its-kind study that shows that BMI measurements in infants may be more useful in determining obesity by age 2 than the current American Academy of Pediatrics guidelines.

While Emily O’Connell, MD, a pediatrician at Falmouth Pediatrics does not advise parents to perform BMI calculations on their infants, she does believe the new research may add support to a new way of assessing infants’ weight in the future.

“I think it will be interesting to see what we’re doing in terms of measuring infants in five years, because I think it will be probably be different than what we are doing now,” she said.

The study, published by the Children’s Hospital of Philadelphia reviewed medical records of 74,000 full-term infants during their first two years of well-baby visits. They compared weight-for-length measurements to “BMI-based estimates” of fat.

The American Academy of Pediatrics and the Centers for Disease Control and Prevention guidelines call for the use of gender-specific weight-for-length charts to map the growth of infants under the age of 2. The guidelines do not include the use of BMI before 2 as a measure of growth or predicting obesity.

Weight-for-length (WFL) percentile charts map the trend of the infant’s weight as compared to length over time.

BMI uses weight and height, not length, in its calculation. Height is measured when a child is standing whereas length is measured when the baby is lying down. The two are not interchangeable, according to the CDC.

The research showed that a high BMI at 2 months of age was more accurate at predicting obesity at 2 years than the WFL chart. The study also showed that both types of measurements were equal predictors at age 6 months.

Parents Shouldn’t Become Too Concerned

While, the research is enlightening, Dr. O’Connell cautions parents against becoming too concerned about doing BMI measurements on their baby.

“Every infant is different and it is much more important to me how they are doing compared to their own weight gain as opposed to comparing it to a specific monograph,” she said. For infants from 0-6 months, generally less than one year, she does not recommend any intervention in terms of dietary modifications, she said.

Dr. O’Connell is more comfortable with a baby who is consistent with his or her weight gain, even if they start in the 95th percentile on the WFL chart. She becomes a little concerned when the infant starts out in the 5th percentile, for example, and then moves into the 25th and then 50th percentiles.

“Then I start thinking there is something we need to be doing differently,” Dr. O’Connell said. “Is there something we need to address?”

There are certain feeding habits that parents may want to avoid, in order to keep their baby within a healthy weight range, she said.

“The one thing we have found in being a risk factor for excessive weight gain is putting baby cereal in the bottle with formula or breast milk. Some babies need that additional help when they have reflux, but other than that, they don’t need cereal in the bottle.”