Low Birth Weight, Poor Weight Gain in First Year Predict Poor Growth in CF Infants, Study Shows

Low birth weight and poor weight gain in the first year of life in infants with cystic fibrosis (CF) predict poor growth rates due to pancreatic dysfunction, a study has found.

The study, “Factors affecting the growth of infants diagnosed with cystic fibrosis by newborn screening,” was published in the journal BMC Pediatrics.

Newborn screening (NBS) in the first few weeks of life has transformed the care of children with CF. It has led to better lung function and improved long-term survival, which has been shown to be closely related to nutritional status. 

Despite these advances, some CF infants diagnosed by NBS do not prosper, due to factors such as respiratory infections, diet, inconsistent use of medications, or other environmental exposures.

To optimize the health of CF infants, it would be helpful for clinical staff to know which of these factors has the most significant impact — enabling children with a higher risk of growth problems to be identified and more carefully monitored.

To find which factors would be useful in predicting growth outcomes in CF children, researchers based at Keele University in the United Kingdom collected information on NBS, demographics, microbiology, and growth of a group of 129 CF children who attended the Birmingham Children’s Hospital or Royal Stoke University Hospital in the U.K.

All children began standard CF treatment following diagnosis. 

Demographic information included gender, ethnicity, weight at birth and at the first clinical visit, CFTR mutations, sweat chloride levels, immunoreactive trypsinogen (CF marker) levels, the presence of thick intestinal mucus (meconium ileus), fecal elastase (marker for pancreatic dysfunction), and mode of feeding (breast milk or formula, or both).

Growth measurements, as determined by weight and length, were recorded during the first two years of life. The age at which the infants were first diagnosed with Pseudomonas aeruginosa or Staphylococcus aureus infection was also recorded. 

Of the children selected, 63 were girls and 66 were boys, with a median age at diagnosis of 22 days. Most of the children were Caucasian (121 out of 129).

Using the fecal elastase test, the children were divided into two groups based on whether or not they had developed exocrine pancreatic insufficiency (EPI) — a blockage of pancreatic digestive enzymes by thick mucus. Of these, 113 children were pancreatic insufficient, and 16 were pancreatic sufficient (did not have EPI).

Consistent with previous reports, the researchers observed that the CF children in the cohort analyzed had lower birth weights compared to non-CF children. 

Following the first visit to the clinic, 29 infants were reported to be breastfed, 60 fed with formula, and 40 with both. There was no difference in feeding modes between pancreatic insufficient and pancreatic sufficient groups, and the method of feeding was not found to be a predictor of CF infant growth. 

While birth weight was not significantly different between pancreatic insufficient and pancreatic sufficient groups, there was a difference by the time of the children’s first clinic visit. Children in the pancreatic insufficient group weighed less (3.42 kg versus 4.60 kg in the pancreatic sufficient group), indicating that pancreatic dysfunction had a clear effect on growth. 

Despite being treated with pancreatic enzyme replacement therapy (PERT), infants in the pancreatic insufficient group had a significantly lower weight and height in the first year of life compared with pancreatic sufficient infants.

However, this difference was reduced in the second year with prolonged PERT and nutritional support. 

In addition to birth weight and weight gain in the first year, other factors such as fecal elastase (a test to assess pancreatic enzymes in stool samples) and sweat chloride levels, as well as infections were identified as predictors of future growth in CF children. 

“The presence of certain factors, most already identifiable at the first clinic visit, can be used to identify infants at increased risk of poor growth,” the researchers said, adding that these factors “should enable focused interventions by clinicians and dietitians to optimize nutritional outcomes.” 

“The possible effect of CFTR on antenatal [prenatal] growth, and the role of other factors such as adherence to treatment and socioeconomic status on infant growth, warrants further investigation,” the team added.