Feeding Method, Nicotine Exposure, and Growth during Infancy

Area of Science:

• Pediatrics
• Public Health
• Environmental Health

Background:

• Maternal smoking during pregnancy and postpartum is a significant public health concern.
• The impact of maternal smoking on infant growth, particularly through breastfeeding, requires further investigation.

Purpose of the Study:

• To determine if infants breastfed by smokers are at risk for accelerated weight and length gain.
• To assess if rapid infant growth is attributable to the ingestion of smokers' breast milk.
• To explore the implications of these findings for breastfeeding practices among smokers.

Main Methods:

• Utilized data from the Norwegian Mother, Father and Child Cohort Study and Medical Birth Registry of Norway (n=54,522).
• Examined infant growth (weight, length, weight-for-length z-score) in relation to maternal smoking levels (0, 1-10, >10 cigarettes/day) and feeding method (breastfed, formula fed, mixed fed).
• Employed generalized linear models with interaction terms to evaluate the effect of maternal smoking on growth via breast milk.

Main Results:

• Breastfed infants of light and heavy smokers showed increased weight-for-length z-score (WFLZ) gains (0.05 and 0.13, respectively).
• Mixed-fed infants of heavy smokers also exhibited increased WFLZ gain (0.10).
• Maternal smoking did not predict rapid growth in exclusively formula-fed infants. Interaction models indicated that infants breastfed by heavy smokers gained weight (100g) and length (2.8mm) attributable to ingesting smoker's breast milk.

Conclusions:

• Infants breastfed by smokers experience accelerated growth, with a portion of this growth linked to the ingestion of smokers' breast milk.
• For infants breastfed by light smokers, these growth gains fall within normal patterns for healthy, breastfed infants.