Several limitations of the current study should be noted. It
is possible that the generalizability of the findings may be limited
to treatment-seeking women who quit smoking early in pregnancy,
and may not generalize to other groups of women, such
as those who quit smoking later in pregnancy or those who do
not choose to participate in smoking cessation treatment. Furthermore,
the failure of many participants to attend the 8 weeks
postpartum visit resulted in some missing breast-feeding status
data. Although no demographic or socioeconomic differences
were found between those who provided information on breastfeeding
status and those with missing breast-feeding status, participants
were found to differ in the number of cigarettes
smoked per day and the time until first cigarette smoked in the
morning (i.e., measures of nicotine dependence). As such, these
variables were included as covariates in all models to adjust for
differences. However, it is possible that missing data occurred as
a result of other unobserved variables for which we were not
able to adjust. The current study also did not evaluate the influence
of breast-feeding duration or exclusivity on postpartum
smoking abstinence. Some research suggests that breast feeding
for ≥6 months may have a greater impact on smoking cessation
than breast feeding for shorter durations (Kaneko et al., 2008).
It is also possible that exclusive breast feeding may be a more
effective deterrent of tobacco use than mixed breast/formula
feeding because exclusively breast-feeding women who use
tobacco would have greater difficulty avoiding or minimizing
infant exposure to nicotine.