Household Smoking And Breastfeeding Duration Among Hong Kong Chinese Women: A Prospective Cohort Study

Abstract

Background Maternal smoking or the inhalation of ambient cigarette smoke remains an important public health problem that affects child health with potential lifelong consequences. Hong Kong is one of the most densely populated cities in the world, and living with extended family members is common. Many pregnant women are exposed to secondhand smoke from household and family members. Thus, the aim of this study was to examine the effect of maternal, paternal, and other household smokers on the duration of breastfeeding in Hong Kong. Methods This analysis was based on a prospective cohort study. From 11th October 2011 to 31st May 2012, mother–infant pairs were recruited during the postnatal hospital admission from four geographically distributed public hospitals in Hong Kong. Participants were Cantonese speaking Hong Kong residents who gave birth to a full-term, singleton infant, who intended to breastfeed, and had no serious medical or obstetric complications. Exclusion criteria were admission to the special care nursery for more than 48 h after birth or admission to the neonatal intensive care unit. Data were collected directly from participants during postnatal hospitalisation and after discharge through telephone follow-up. In-hospital data collection included basic demographic details, maternal and infant data, and in-hospital feeding data. Follow-up data included infant feeding status at 1, 2, 3, 6, 9, and 12 months post partum or until breastfeeding was stopped. Participants were asked whether they smoked during pregnancy, whether their partner or husband smoked, and whether any other family members living in the same household smoked. Smoking was then categorized as total number of smokers living in the same household (zero, one, or two or more). The primary outcome was the duration of any and exclusive breastfeeding up to 12 months post partum. The study was approved by the Institutional Review Board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster and from all study hospitals. Informed written consent was obtained from each participant. Findings We recruited a total of 1277 mother–infant pairs admitted to the obstetric units of four public hospitals in Hong Kong and followed them up by telephone up to 12 months post partum. After further exclusion of 37 (3%) participants with no further contact after hospitalisation, 1240 mother–infant pairs were successfully followed up. Of the mothers, 806 (65%) reported no smokers in the household, 337 (27%) reported one smoker in the household, and 95 (8%) reported two or more smokers in the household. We noted a pattern of increasing number of smokers living in the household associated with progressively shorter duration of any and exclusive breastfeeding. However, the effect of number of smokers living in the household on the overall duration of exclusive breastfeeding was not statistically significant. A Kaplan-Meier survival curve showed that the number of smokers living in the household was associated with progressively shorter duration of any breastfeeding. When compared with mothers who reported no smokers in the family, those exposed to two or more family members that smoked were almost 40% more likely to stop any breastfeeding (adjusted hazard ratio 1·37, 95% CI 1·06–1·76) within 12 months. Interpretation We found that mothers exposed to a greater number of smokers in the household had a significantly higher risk of breastfeeding cessation. Practitioners can assess the smoking patterns of pregnant women and their family members and provide smoking cessation education and support to this high-risk group. Future research is needed to identify the physiological factors associated with smoking on breastfeeding practices.