BACKGROUND AND PURPOSE: 

• Environmental contaminants, including tobacco smoke, lead and phthalates, are transferred from mothers to infants transplacentally and via breast milk 
• Most studies have evaluated impact of toxins on breast feeding by focusing on exposure via breast milk 
• Few studies have focused on low-level exposures to toxins in the prenatal period  
• Rosen–Carole et al. (Maternal and Child Health Journal, 2017) assessed the impact of low prenatal exposure to common toxins (tobacco smoke, lead, and phthalates) on breastfeeding exclusivity and duration 

METHODS: 

• Prospective cohort study 
• Health Outcomes and Measures of the Environment (HOME) Study (2003-2006) 
• Serum and urine samples were collected at approximately 16 (range 10-23) and 26 (range 19-35) weeks gestation and at delivery  
• Women were included who lived in a home built in 1978 or before, when lead-based paints were frequently used  
• Maternal infant feeding interviews were conducted eight times through 30 months postpartum, beginning 4 weeks post partum   
• Tobacco smoke  
  • Passive smoke exposure defined as serum cotinine levels of 0.015-3.0 μg/mL)  
  • Active smokers defined as serum cotinine concentrations >3.0 μg/mL 
• Cotinine, lead, and phthalates measured at the CDC Division of Laboratory Sciences  
• Primary outcomes were duration of any and exclusive breastfeeding 

RESULTS: 

• Samples were collected from 373 women; 302 breastfed their infants  
• As serum cotinine concentrations increased, duration of any breastfeeding decreased 
  • 29.9 weeks unexposed vs. 24.9 weeks with passive exposure (p = 0.04) 
• Duration of any breastfeeding was not significantly different between active smokers and the unexposed group but there was a linear trend for increasing cotinine levels (p = 0.03 for linear trend) 
  • Only 12% of women were active smokers and ‘n’ may be too small to detect difference  
• There was no difference in duration for exclusive breastfeeding  
• Prenatal levels of blood lead and urinary phthalate metabolites were not significantly associated with duration of any or exclusive breastfeeding 
• More women in passively and actively exposed groups did not feel they had breastfed for as long as intended compared with unexposed women 
  • 21% felt they did not meet their goals because of return to work while 49% felt their breast milk was insufficient or reported growth failure for their infants 

CONCLUSION: 

• Researchers acknowledge study limitations, including potential lack of generalizability as the HOME cohort generally had lower rates of exclusive breastfeeding and briefer breastfeeding compared to national cohorts 
• This study does not address biologic explanation but other researchers have suggested toxic impact on development of mammary glands during pregnancy or disruption of hormonal signaling  
• Hypothesis supported by at least one animal study  
• Passive exposure to tobacco smoke during pregnancy was associated with shortened duration of any breastfeeding even after adjusting for confounders 

Learn More – Primary Sources:  

Low-Level Prenatal Toxin Exposures and Breastfeeding Duration: A Prospective Cohort Study

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Does Smoking During Pregnancy Affect the Fetal Immune System?

Placenta Previa – Nomenclature, Diagnosis and Clinical Management

Microcephaly – Beyond the Zika Virus