Prenatal exposure to passive smoking and duration of breastfeeding in nonsmoking women: Krakow prospective cohort study

Wieslaw Jedrychowski, Frederica Perera, Elzbieta Mroz, Susan Edwards, Elzbieta Flak, Virginia Rauh, Agnieszka Pac, Dorota Budzyn-Mrozek and Agnieszka Musiał

Archives of Gynecology and Obstetrics, March 2008


Introduction The relationship between tobacco smoking in pregnancy and breastfeeding is of public health importance. The present birth cohort study provided the opportunity to investigate whether the negative relationship between passive smoking measured by the cotinine concentrations in maternal blood at delivery and breastfeeding in postpartum could also be confirmed in nonsmoking mothers.

Materials and methods The study sample included 441 healthy pregnant women who were recruited in the first and second trimester of pregnancy. Enrolment included only nonsmoking women of the age of 18–35 years with singleton pregnancies, without illicit drug use and free from chronic diseases. After delivery, breastfeeding duration was defined using the answers recorded in the interviews with mothers conducted every 3 months. An infant was considered to be fully breastfed when breast milk was the only source of nourishment. Any breastfeeding was defined as an infant’s being fully breastfed or receiving both breast milk and formula, with or without solids. In the statistical analysis only total duration of breastfeeding up to 6 months was considered for both forms of breastfeeding. Subjects were categorized into environmental tobacco smoke (ETS) exposure groups according to maternal blood cotinine level at delivery or self-reported exposure to ETS during pregnancy.

Results The adjusted relative risk of discontinuation of any breastfeeding after infant’s first 6 months was more than two times higher (OR = 2.42; 95% CI: 1.42–4.14) in women whose blood cotinine level at delivery was above 75th percentile of cotinine distribution (>0.15 ng/mL); the corresponding risk of discontinuation of full breastfeeding was OR = 1.71; 95% CI: 1.03–2.82. Estimated relative risk of discontinuation of any breastfeeding based on self-reported ETS was also significant but much less marked; the corresponding risk of discontinuation of full breastfeeding was insignificant.

Conclusion The results obtained support the hypothesis that ETS may affect breastfeeding duration and support the avoidance of passive smoking as a necessary additional measure for breastfeeding promotion.