Vitamin D levels in newborns linked to risk of RSV

Newborns with low levels of vitamin D may be at increased risk for developing severe respiratory syncytial virus (RSV) infection with bronchiolitis during their first year of life, suggests a Dutch prospective birth cohort study.

Researchers at Wilhelmina Children’s Hospital in Utrecht studied the relation between concentrations of 25-hydroxyvitamin D (25-OHD) in cord blood plasma and lower respiratory tract infection (LRTI) caused by RSV in 156 healthy neonates. They defined RSV LRTI on the basis of a daily log by parents of their child's LRTI symptoms and the simultaneous presence of RSV RNA in a nose-throat specimen.

Eighteen (12%) infants developed RSV LRTI during their first year. They had lower concentrations of 25-OHD than babies without RSV LRTI (65 nmol/L vs 84 nmol/L). Babies born with 25-OHD concentrations lower than 50 nmol/L were 6 times more likely to develop RSV LRTI during their first year than those with concentrations of 75 nmol/L or higher. Cord blood concentrations of 25-OHD were strongly associated with maternal vitamin D3 supplementation during pregnancy. The study was published online May 9 in Pediatrics.

Only 46% of women in the study cohort reported taking vitamin D supplements while they were pregnant.

Of the 156 neonates studied, 27% had 25-OHD concentrations below 50 nmol/L (inadequate), 27% had concentrations between 50 nmol/L and 74 nmol/L (considered inadequate by some experts), and 46% had concentrations of at least 74 nmol/L (adequate). Infants with concentrations in the controversial 50 nmol/L to 74 nmol/L range did not demonstrate increased risk of RSV LRTI.

Pregnant women should continue to follow expert guidelines on vitamin D intake pending further research, recommends senior investigator Louis Bont, MD. The US Institute of Medicine recommends 600 IU per day of vitamin D with an upper daily limit of 4,000 IU.