Passive smoke and low birth weight. Evidence of a threshold effect

Arch Fam Med. 1994 Oct;3(10):875-8. doi: 10.1001/archfami.3.10.875.


Objective: To examine the relationship between different levels of maternal passive tobacco smoke exposure and low-birth-weight infants.

Design: Data from the National Health Interview Survey were analyzed.

Participants: Women who did not smoke during pregnancy and gave birth to children within 6 years of the date of the interview in 1988 were the source of the data (N = 3253). Passive smoke exposure was categorized as very low, low, moderate, and high.

Main outcome measures: Low-birth-weight (< 2500 g) infants and mean birth weight in grams.

Results: There was no significant difference in the rates of low birth weights when passive smoke exposure was dichotomized as no exposure vs some exposure (5.0% vs 5.6%, respectively; P = .55). However, when the level of exposure to passive smoke was considered as a continuum, high exposure was associated with both lower mean birth weights in grams (P = .007) and a greater likelihood of a low birth weight (P = .01), indicating a threshold effect of exposure. Logistic regression analysis indicated that, after controlling for potentially confounding variables, individuals with high exposure are 1.57 times (95% confidence interval [CI], 0.98 to 2.51) as likely as those with low exposure to have a low-birth-weight infant. Among nonwhites, individuals with high exposure to passive smoke were 2.31 times (95% CI, 1.06 to 4.99) as likely to have a low-birth-weight infant as those with low exposure to passive smoke.

Conclusion: A threshold effect of exposure to passive smoke and low birth weight was discovered.

MeSH terms

  • Adolescent
  • Adult
  • Confounding Factors, Epidemiologic
  • Dose-Response Relationship, Drug
  • Environmental Exposure / adverse effects*
  • Female
  • Humans
  • Infant, Low Birth Weight*
  • Infant, Newborn
  • Logistic Models
  • Maternal Exposure / adverse effects*
  • Middle Aged
  • Pregnancy
  • Prenatal Exposure Delayed Effects
  • Tobacco Smoke Pollution / adverse effects*


  • Tobacco Smoke Pollution