Postpartum Smoking Relapse Prevention by Breastfeeding Promotion
Phase: NA
Conditions: Smoking, Cigarette, Breastfeeding
Sponsor: State University of New York at Buffalo

COVER PAGE 
 
Study Title: Postpartum Smoking Relapse Prevention by Breastfeeding Promotion 
 
NCT number: NCT04670822 
 
Document Date: March 15, 2017 
 

RESEARCH STRATEGY 
1. Significance  
Both opportunities and challenges exist for smoking cessation during pregnancy and postpartum. High 
motivation to quit during pregnancy is often followed by high chance of relapse during postpartum. About 23% 
of U.S. women smoke before pregnancy, and 54% of them report quitting smoking during pregnancy.1 But 
most of women who quit smoking during pregnancy return to smoking (“relapse”) after delivery, e.g., 45%, 
70%, and 81% relapse by 6, 9, and 12 months postpartum, respectively.2,3 Postpartum smoking relapse not 
only limits the benefits of smoking abstinence to the mother, but also has serious negative consequences for 
child health and development via tobacco metabolites in breast milk and ambient air.4-6 Child risks include fast 
infancy weight gain7 and childhood overweight5 as shown in our studies, infant respiratory illness such as 
asthma,8 and sudden infant death syndrome.9 Preventing postpartum smoking relapse remains a challenge for 
research and clinical practice. According to a recent review of 32 relevant studies, few existing 
pharmacological, behavioral, and contingent incentive-based interventions have been proven to be effective on 
preventing smoking relapse in long-term postpartum period (e.g., 9 months or longer),10 although several 
incentive-based studies were still effective up to 6 months postpartum (longer assessment unavailable).11-14 
Indeed, in a large trial published recently, the intervention focusing on ex-smoking mothers’ concerns about 
mood, stress, and weight did not improve smoking abstinence at 12 months postpartum.15 Novel and effective 
interventions are urgently needed to address the large public health issue of postpartum smoking relapse.   
Numerous stressors in postpartum life and negative affect such as depression, anxiety, anger, and fear 
are reported as common triggers for postpartum smoking relapse. Interestingly, breastfeeding mothers tend to 
have lower perceived stress16-18 and less negative affect including depression19-21 and anger,19 than formula-
feeding mothers. While the directions of these associations are difficult to determine from observational 
studies, in a within-subject design study, maternal negative affect decreased after a breastfeeding episode in 
the same mothers, whereas maternal positive affect decreased after a formula-feeding episode.17 In addition, 
early termination of breastfeeding is associated with increased depression and anxiety.18,22 These 
breastfeeding-related emotional benefits may be attributed to unique neuroendocrine changes to maintain 
breastfeeding, especially higher oxytocin and prolactin levels.23-25 These neuroendocrine and psychological 
mechanisms may explain our and others’ observation that smoking relapse is much less common (30-60% 
lower risk) among breastfeeding mothers than formula-feeding mothers.2,26,27 Therefore, it is reasonable to 
hypothesize that a breastfeeding promotion intervention can reduce the risk of postpartum smoking relapse 
through increased oxytocin and prolactin while decreased maternal stress and negative affect. Our application 
is the first randomized controlled trial to test this promising hypothesis.  
In a pilot survey (Dr. Wen as PI), we found poor breastfeeding knowledge among 21 pregnant and 18 
postpartum women who quit smoking during pregnancy. Only 28.6% agreed “Babies should be exclusively 
breastfed for the first 6 months (current clinical guidelines28,29)”, 52.4% agreed “The best way to feed a baby is 
breastfeeding”, and 38.1% agreed “If a baby is breastfed he or she will be less likely to get diarrhea”. Their 
intention to breastfeed was also relatively low: only 42.9% planned to breastfeed exclusively in the first weeks 
after delivery, and only 9.5% planned to exclusively breastfeed for 6 months. Their actual breastfeeding 
practice was even lower: only 22.2% and 0% breastfed exclusively in the first week and 6 months after 
delivery, respectively. Quitters tend to wean their infants sooner than nonsmokers, and their breastfeeding rate 
at 4 months postpartum is similar to that of continuous smokers’.30 These consistent data suggest an urgent 
need to promote breastfeeding among women who quit smoking during pregnancy. One of our key team 
members, Dr. Yukiko Washio (Co-I), has developed, tested, and published a highly effective intervention 
funded by NIH to increase breastfeeding duration among low income mothers. For instance, the breastfeeding 
rate at 6 months postpartum was 72% in the intervention group, compared to 0% in the usual care group.31 We 
plan to modify her intervention to promote breastfeeding among ex-smoking mothers in the proposed project.  
Conceptual model (Figure 1).  Through suckling stimuli and intimate mother-infant contact (e.g., infant 
hand massage and skin-to-skin contact, breastfeeding promotes the release of two key lactation hormones 
from the pituitary gland: prolactin (hormone for milk synthesis) and oxytocin (hormone for milk ejection).23,32-35 
Both oxytocin and prolactin can reduce maternal stress response through dampening hypothalamic-pituitary-
adrenal (HPA) activity, which can lead to lower and/or fewer surges of adrenocorticotropic hormone (ACTH) 
and cortisol.36,37 Oxytocin and possibly prolactin also decrease maternal negative affect19-21,38 through reducing 
amygdala activation.39,40 In addition, breastfeeding helps to enhance mother-infant bonding,41-43 possibly 
through the activities of oxytocin in brain to decrease aggressive responses toward offspring.38,44-46 Intervention 
targeting mother-infant bonding can decrease postpartum smoking relapse up to 8 weeks postpartum,47 
possibly because a strong mother-infant bond can foster positive mother-infant interaction.48 The positive 

mother-infant interactions may serve as an alternative reward pathway that may decrease frequency and 
intensity of cravings for cigarettes. It could potentially shift the focus of ex-smoking breastfeeding mothers’ 
dopamine reward system from smoking to caring for the child.48-50 As positive mother-infant interactions 
increase, the mother’s investment (e.g., time, attention, money) in her child may increase, while her cravings 
for smoking are expected to diminish.48,51,52 The mother’s process of replacing cravings for smoking with 
increasing investment in the child and building a positive caregiving relationship may be gradual but may also 
be sustainable over time,48 which is indirectly supported by previous research in which parenting intervention is 
associated with substance use reduction53-55 and pup suckling is more rewarding than cocaine in the 
immediate postpartum period.56 This natural alternative reward system (positive mother-infant interaction) 
along with low 
maternal stress and 
negative affect may 
help breastfeeding 
mothers to achieve 
long-term 
postpartum smoking 
abstinence.  
 
2. Innovation Our 
proposed project is 
innovative in several 
ways. First, it is the 
first randomized 
controlled trial to assess the effect of breastfeeding promotion on postpartum smoking relapse. It can help to 
yield causal evidence by overcoming self-selection bias and confounding (e.g., health motivation, socio-
economic status [SES], partner and family support) in previous observational research. Secondly, we will 
collect pilot data to examine neuroendocrine (oxytocin and prolactin), behavioral (mother-infant interaction), 
and psychological (mother-infant bonding, stress, and negative affect) mechanisms through which 
breastfeeding may reduce risk of postpartum smoking relapse. Thirdly, this is a pioneering study to combine 
contingent incentives with other intervention strategies such as education, counseling, support, and early 
limited formula milk via syringe to further improve breastfeeding practice among disadvantaged mothers.  
 
3. Approach 
3.1 Research Design. 3.1.1 Overview. This is a randomized controlled trial to prevent postpartum smoking 
relapse by breastfeeding promotion. The intervention group (N=30) will receive multicomponent breastfeeding 
intervention from late pregnancy to 6 months postpartum, while the usual care control group (N=30) will only 
receive minimum breastfeeding education. The key outcome is the timing of postpartum smoking relapse. 
3.1.2 Recruitment. We will recruit 60 pregnant ex-smokers from Erie County and Niagara County, NY. 
Recruitment flyers will be distributed around the communities (e.g., churches, bus/subway stops, laundromats, 
grocery stores, thrift stores, community centers) and organizations providing basic services (e.g., social 
services, WIC, job training) to low income pregnant women.57 Recruitment flyers will also be displayed in 4 
large city OB/GYN clinics. Health professionals at these clinics will pass our recruitment materials to ex-
smoking patients. We will also send an invitation letter to potentially eligible pregnant women in these clinics.58-
60 The PI has successful experience in recruiting 50 pregnant smokers for his NIH funded study on smoking 
cessation during pregnancy over 6 months from 2 obstetric clinics (see Letters of Support from clinics).61,62 
Social media such as Facebook will also be used. Assuming a rate of 23% maternal smoking at conception 
and 54% smoking cessation rate during pregnancy,1 we estimate 1,490 out of about 12,000 newborns63 will be 
born to mothers who quit smoking during pregnancy within 1 year in the two counties. We assume 60% of 
these mothers (N=894) will be exposed to recruitment materials, and then 30% (N=268) are interested in this 
project. Therefore, it is feasible to recruit 72 (60 + 20% attrition) eligible participants within 1 year.  
3.1.3 Screening. Interested participants will sign consent forms and complete a survey on socio-demographics, 
pregnancy, medical history, mental health, history and status of cigarette smoking, use of other tobacco or 
nicotine products, alcohol and other substance use, and infant feeding plan. Those who had quit smoking 
cigarettes within 3 months before or during this pregnancy will be invited for lab screening to verify their current 
non-smoking status by urine cotinine (metabolite of nicotine). Collateral reports (e.g., from employer, partner, 
friend, or relative) or medical records will be used to verify their previous smoking history.64 Eligible participants 
* Other hormonal mechanisms, such as progesterone, estrogen, ACTH, cortisol, and tetraiodothyronine 
(T4), will be included in the larger R01 grant. 
Breastfeeding 
(Oxytocin ↑, 
Prolactin ↑) 
Maternal stress ↓ 
Maternal negative affect ↓ 
Maternal bonding with 
the infant ↑ 
Long-term 
postpartum 
smoking 
abstinence 
Figure 1. Conceptual Model for 
Breastfeeding and Smoking Abstinence* 
Confounders (e.g., health motivation, 
SES, partner and family support) 
Positive mother-
infant interaction 
 - Alternative reward 
to decrease 
smoking cravings 

must be at 28 weeks of pregnancy or earlier to ensure adequate time for prenatal breastfeeding intervention. 
Exclusion criteria are teen pregnancy (<18 y); current use of other tobacco or nicotine products; medical 
conditions contraindicating breastfeeding such as HIV infection, active tuberculosis, and breast removal;28 
current heavy drinking (more than 2 drinks a day); current use of other psychoactive substances;65 being 
strongly against breastfeeding; and non-English speakers. To increase the possibility to obtain a representative 
sample of the generable population, the study will be advertised as a program to promote healthy infant 
feeding among pregnant women without requiring breastfeeding intention or mentioning smoking relapse 
prevention. We will not exclude women without current intention to breastfeed (28.6% in our pilot survey), 
unless they are strongly against breastfeeding (4.8%). Similarly, we will not exclude women who plan to 
relapse after delivery (0% in our pilot survey), as our breastfeeding promotion may motivate them to maintain 
abstinent for a longer period especially if they know tobacco metabolites are concentrated in breast milk.4  
3.1.4 Pre-test visit. During this visit, we will measure the participant’s urine cotinine, height, and body weight. 
Participants will complete a survey on smoking temptations, nicotine dependence before quitting, smoking 
cessation history, self-efficacy to maintain smoking abstinence, smoking environment including partner 
smoking behaviors, breast health, breastfeeding knowledge, breastfeeding history, relationship with partner 
and other family members, social network, stress, negative affect, physical activity, sleep, and diet. 
3.1.5 Randomization. At 28 weeks of pregnancy, eligible participants will be randomized into either the 
intervention group (N=30) or the control group (N=30) using a sequence of random numbers in blocks of 2, 
which can ensure equal or close numbers of participants between the two groups throughout the project. 
3.1.6 Intervention. a) Intervention group. The goal of our breastfeeding intervention is consistent with AAP28 
and ACOG29 guidelines: exclusive breastfeeding for the first 6 months of life, with continued breastfeeding as 
complementary foods are introduced through the infant’s first year of life, or longer as mutually desired by the 
mother and her infant. Participant will complete 13 one-hour intervention visits: 5 during pregnancy and 8 in 
postpartum. Prenatal breastfeeding education will be weekly for 5 weeks at the PI’s lab. After delivery, we will 
meet the participant at her home in 1 week, 2 weeks, and 1 month; and then monthly at the PI’s lab until 6 
months postpartum. Participants will receive $15/visit compensation. Our team has rich experience in running 
behavioral interventions for the target population, for instance, most participants (73.9%) in the PI’s smoking 
cessation study have completed 35 one-hour prenatal intervention visits and 12 monthly 1.5-hour postpartum 
follow-up visits with similar compensation ($15/hour).61,62 The breastfeeding intervention components will 
include prenatal breastfeeding education, postnatal lactation counseling, family/peer/employer support, 
contingent financial incentives, and early limited formula milk via syringe (optional for at-risk infants).  
Component #1 - Prenatal breastfeeding education: To maximize the effect, breastfeeding education will 
start in late pregnancy (28+ weeks) when the mother and family seriously plan on infant feeding.66 The 
breastfeeding plan will cover breastfeeding on demand, pain management, skin-to-skin contact, breastfeeding 
tips after cesarean section, lactation support, breastfeeding away from home, breast pump, maternity leave, 
and back-to-work scheduling. Educational approaches will include readings with quizzes ($2 reward if passed), 
discussion, video, demonstration and practice with a baby simulator. Prenatal breastfeeding education will be 
delivered in a group with 6 pairs of participants and their family supporters per group. Physical examination of 
breasts and nipples will be conducted by a certified lactation counselor (CLC) to address potential issues 
including infectious conditions, dermatitis, breast masses, breast surgery, and flat or inverted nipples.  
Component# 2 - Postnatal lactation counseling: A part-time CLC will be hired to provide timely and 
individualized postnatal lactation counseling. She will monitor each participant’s breastfeeding progress, help 
them initiate breastfeeding immediately after delivery, correct myths and flaws, answer questions, and offer 
suggestions and tips to solve potential problems. Besides face-to-face meetings, text messages and phone 
calls will also be used to provide timely assistance of lactation practice and routine checking of feeding status.  
Component #3 - Family/Peer/Employer support: The participant will nominate a family supporter for her 
breastfeeding. The family supporter will receive our training for skills in supporting the participant’s decision 
and effort to breastfeed. Other family members will also receive a breastfeeding support booklet. The PI has 
successful experience of training 16 family supporters for our Pregnancy and Smoking Cessation Study.61 In 
addition, we will encourage participants to attend Buffalo’s Baby Cafés (6 sites), a breastfeeding drop-in 
support group, to seek further support from lactation counselors and other breastfeeding mothers (peers).67,68 
Particularly, the PI has been collaborating with one of these sites, the Durham's Central City Baby Café69 (see 
Letter of Support). This Baby Café has been helping 214 of 221 mothers (96.8%) to breastfeed successfully 
since 2013. A booklet on benefits of breastfeeding for business, how to support a nursing mother in workplace, 
laws and policies of promoting breastfeeding will be available to the participant’s employer.70 

Component #4 - Contingent financial incentives: Participants will receive incentives for breastfeeding if 
they are able to nurse or to provide milk by pumping in the presence of a female research staff. In the Co-I Dr. 
Washio’s effective intervention (e.g., 72% breastfeeding rate at 6 months postpartum vs. 0% usual care),31 
contingent incentives start at $20 at the end of first month and increase by $10 every month until the end of 6 
months postpartum. We will adapt this incentive schedule for the proposed project by adding two home visits in 
week 1 and week 2 postpartum for breastfeeding consultation with $20 incentive for breastfeeding, given that 
the first month postpartum is critical to address high risk of breastfeeding discontinuation and smoking 
relapse.71,72 The family supporter will also receive $10 incentive/month if the participant is still breastfeeding.  
Component #5 - Early limited formula milk (ELF) via syringe: This component is optional and is only 
reserved for at-risk infants with 5% or more birth weight loss within the first 2 days of life when the mother 
decides to add formula.73 The goal of ELF is to ensure supplemental use of formula to help the at-risk infant 
grow but will not interrupt the success of breastfeeding. Specifically, the mother should always breastfeed the 
infant first. If needed, a limited amount (10.0 mL or less) of formula milk is then complemented. The formula 
milk is administered via syringe rather than baby bottles, which can prevent nipple confusion. ELF will be 
discontinued once breast milk can meet the infant’s need, usually within 2 weeks. ELF has been shown to 
increase exclusive breastfeeding rate (79% vs. 42% usual care) at 3 months postpartum for at-risk infants.73 
b) Control Group. Participants in the control group will receive a brief pamphlet on the benefits and 
skills of breastfeeding. They will complete the same frequency of study visits as the intervention group to 
monitor their feeding plan/practice with a fixed compensation ($15/visit), regardless of feeding practice.  
c) Fidelity and quality control. Step-by-step instructions will be used for each visit. The PI will train all 
research staff. Evaluation will be conducted via exams and trial runs before their interacting with participants. 
All visits will be audio-recorded for quality assurance and 20% of audio files will be reviewed by the PI.  
Comments. We decided not to include any education or intervention directly targeting on smoking 
relapse. This will allow us to test the independent effect of breastfeeding promotion on smoking relapse.  
3.1.7 Follow-up. To evaluate sustainability of the effects of breastfeeding promotion on smoking relapse, we 
will follow participants and infants in 9 months postpartum (i.e.,3 months after breastfeeding intervention ends). 
3.1.8 Outcome measures. The key outcome measures include timing of postpartum smoking relapse (primary) 
and breastfeeding duration (secondary) derived from data repeatedly collected throughout the study (Table 1). 
Outcomes will be assessed by graduate research assistants who are blinded to group assignments.  
Table 1. Schedule for outcome and mediator measures 
 
Pregnancy 
Postpartum (W-week, M-month) 
Measure 
Enrollment 
(pre-test) 
W1 
W2 
M1 
M2 
M3 
M4 
M5 
M6  
(post-test) 
M9  
(follow-up) 
Outcomes  
 
 
 
 
 
 
 
 
 
 
    Smoking status 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
    Breastfeeding (BF) status 
BF intention 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Mediators 
 
 
 
 
 
 
 
 
 
 
    Oxytocin and prolactin 
 
 
 
X 
 
X 
 
X 
 
 
    Mother-infant bonding 
 
X 
X 
X 
X 
X 
X 
X 
X 
X 
    Mother-infant interaction 
 
 
 
X 
 
X 
 
X 
 
 
    Maternal stress 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
    Maternal negative affect 
X 
X 
X 
X 
X 
X 
X 
X 
X 
X 
Timing of maternal postpartum smoking relapse. The participant will use a calendar to record the daily 
number of cigarettes smoked, if any, throughout the study period. Based on SRNT guidelines,74 the date of 
postpartum relapse will be defined as the first day after delivery on which an ex-smoker has smoked for 7 
consecutive days, or has smoked at least once each week over 2 consecutive weeks. Similar definitions were 
used in previous studies on postpartum smoking relapse.15,52,75,76 The self-reported smoking abstinence will be 
biochemically confirmed by urine cotinine tests with HPLC-MS/MS assay performed by an outside laboratory 
(Kaleida Health Lab, Buffalo, NY). As recommended by SRNT,77 a cut-off point of 50 ng/mL urine cotinine will 
be used to define current smoking. There is a possibility that some participants may relapse during pregnancy 
(prenatal smoking relapse). If the relapse happens before randomization, they will be removed from this study. 
Otherwise, they will continue to receive breastfeeding intervention and be included in intent-to-treat analysis. 
Breastfeeding duration. We will measure the initiation, duration, and exclusivity of breastfeeding by 
interviewing the mother at each postpartum visit using a questionnaire modified from 2 US national birth 
cohorts.78,79  Postpartum mothers will report their current feeding method, frequency, and duration of 
breastfeeding and/or formula use. Breastfeeding status will be visually verified by a female research staff, 

looking for one of the following indicators of successful breastfeeding in the infant – audible swallowing, a 
regular suck/swallow/breath pattern, or visible milk in the infant’s mouth after they are not latched anymore.31  
For a mother who pumps milk, staff will observe pumping combined with the resulting milk being fed to the 
infant. This visual verification of breastfeeding/pumping was acceptable to participants in Dr. Washio’s study.31 
3.1.9 Mediator measures. Maternal plasma oxytocin and prolactin. The release of oxytocin and prolactin is 
often pulsatile and stimulated by suckling or pumping, and also varies across postpartum periods.80-82 To 
capture hormonal changes, we will measure the baseline and peak levels of these two hormones during a 
typical feeding session ($40 extra compensation/session) in 1, 3, and 5 months postpartum (Table 1). The 
hormonal response to feeding will be calculated as the difference between the baseline and the peak during 
feeding. Based on a published protocol (co-authored by Dr. Grewen, Consultant),80 the mother will bring her 
infant to the PI’s lab at 1PM for an observed feeding session in a quiet dedicated room administrated by the PI 
and a phlebotomist. A 20 gauge Venflon cannula will be inserted into the mother’s forearm vein to enable 
multiple blood draws. To reduce the impact of experimental manipulation (e.g., needle stick induced stress) on 
measured hormonal levels, a 10-minute habituation period and another 10-minute baseline rest will be used 
before a 5.0-mL venous blood sample is obtained to measure baseline oxytocin and prolactin. The mother will 
then feed her infant as usual, e.g., breastfeeding, formula feeding, or mixed. Based on previous studies with 6 
or 7 repeated hormonal measures around a feeding episode, we expect the typical peaks to occur at about 3 
minutes for oxytocin80 and 30 minutes for prolactin81,83 after the onset of breastfeeding or pumping. Thus we 
will obtain 5.0-mL blood samples repeatedly at 3 and 30 minutes after the onset of feeding or pumping. Plasma 
oxytocin and prolactin will be assayed at Dr. Grewen’s lab in UNC at Chapel Hill (see Letter of Support). The 
level of oxytocin will be measured by enzyme immunoassay with extraction (Enzo Life Sciences).84 The level of 
detection for oxytocin is 1.1 pg/mL and intra-assay and inter-assay coefficient of variation (CV) are 4.6% and 
8.7%, respectively.80 Prolactin will be measured with commercial radioimmunoassay (MP Biomedicals) with 
level of detection being 1.0 ng/mL and intra-assay and inter-assay CV being 5% and 9%, respectively.85 
Comments. We recognize the timings for peak oxytocin and prolactin vary among individuals. Using 
the average peak times (3 and 30 minutes, respectively) is a cost-efficient way to capture hormonal responses.  
 
Mother-infant bonding. Mother-infant bonding will be measured with the Postpartum Bonding 
Questionnaire (PBQ) at all postpartum visits.86 PBQ is a 25-item scale reflecting a mother’s feelings or 
attitudes towards her baby, such as ‘‘I feel close to my baby’ and ‘‘I regret having this baby’’. Cronbach’s alpha 
was 0.76 for the total PBQ scale, and test-retest reliability was 0.95, 0.95, 0.93, and 0.77 for the 4 subscales 
(impaired bonding, rejection and anger, anxiety about care, and risk of abuse), respectively. PBQ is a valid 
screening tool for bonding disorders86 and is well correlated with Kennerley Blues Scale.87    
Mother-infant interaction. At 1, 3, and 5 months postpartum, maternal and infant behaviors will be 
assessed during observations of mother-infant interactions during free play in the PI’s lab. The observation 
room will be set up with toys on top of a colorful blanket placed on the floor. Mothers will be asked to spend 
some time with their infants as they normally would at home. These interactions will be videotaped for 10 
minutes and independently coded by two coders blinded to group assignment or other information about 
mothers and infants. These observations will be coded using 5-point rating scales originally developed by 
Clark88 and used extensively in our prior studies led by Dr. Eiden (Co-I).89-91 Three composite maternal scales 
will be derived: maternal sensitivity, negative affect, and positive engagement. Three composite infant behavior 
scales will be computed: infant responsiveness, positive affect, and negative affect. These scales are reliable 
and valid across different samples of substance using women, including pregnant smokers.89  
 
Maternal stress. We will measure maternal stress with Perceived Stress Scale (PSS) at enrollment and 
all postpartum visits.92 The 14-item PSS measures subjective stress or the degree to which life situations are 
appraised as stressful. Participants will report how often they have felt upset, nervous, angered, in control, or 
that they have coped effectively in the past month. Cronbach’s alpha of PSS was 0.85 and test-retest reliability 
was 0.85. It was correlated with life-events, depressive and physical symptomatology, and social anxiety.92  
Maternal negative affect. Maternal negative affect will be measured at enrollment and all postpartum 
visits using the Positive and Negative Affect Schedule (PANAS).93,94 The 10 items on negative affect include 
being distressed, upset, guilty, ashamed, hostile, irritable, nervous, jittery, scared, and afraid. Participants will 
rate their experience of each particular emotion in the past few weeks. With this time frame, its Cronbach’s 
alpha was 0.87 and test-retest reliability was 0.48.93 In addition, we will measure maternal anxiety with the 
State-Trait Anxiety Inventory95 and postpartum depression with the Edinburgh Postnatal Depression Scale.96  
3.1.10 Covariates. We consider partner smoking, maternal secondhand smoke exposure, education, 
household income, health motivation,97 perceived social support,98 as covariates. They may confound our 
results and will be controlled in data analysis if not comparable between intervention and control groups. 

3.1.11 Economic costs. We will collect information on intervention (not research and development) costs such 
as personnel, recruitment, materials, compensation, incentives, and transportation. We will include outcome 
costs for formula, medical care of NICU stay and sick child visits, and parental absenteeism for infant illness.99  
3.1.12 Statistical Analysis. Specific Aim 1 (Breastfeeding promotion and postpartum smoking relapse). The 
timing of postpartum smoking relapse (outcome) will be analyzed with Cox regression model by including 
group assignment (intervention vs control), smoking status (1=smoking, 0=non-smoking), the observed time, 
and significant covariates. The proportional hazard ratio of postpartum smoking relapse between two groups 
will be calculated.15 We will estimate Kaplan-Meier survival curves to visually compare smoking trajectories. 
Intent-to-treat analysis will be used with all randomized participants being included in their originally assigned 
groups. Dropouts, losses to follow-up, fetal deaths, and miscarriages will be coded as missing data on smoking 
status. If missing data on smoking status is more than 20%, we will run pattern mixture models and sensitivity 
analyses.13,74,100 A supplemental analysis will be run to examine prenatal smoking relapse during pregnancy.   
Specific Aim 2 (Mediation analyses on mechanisms). We will use dynamic path analysis101,102 to 
examine the mechanisms through which breastfeeding reduces smoking relapse. The dynamic path analysis 
includes simultaneous fitting of the Aalen additive hazards model (the R package ‘timereg') and ordinary path 
analysis (PROC TCALIS in SAS). It fits our survival data with internal time-dependent mediators (e.g., oxytocin 
or prolactin) and a counting process as the outcome (i.e., smoking relapse). Hormonal baseline level and 
response to infant feeding (oxytocin or prolactin) will be included into the model as independent mediators. We 
will estimate the direct, indirect (through one or multiple mediators), and total effects of breastfeeding on 
smoking relapse (Figure 1). The PI has sufficient experience in mediation analysis.103,104  
3.1.13 Sample size. According to the literature,65,66 we estimate 45% rate of smoking relapse by 6 months 
postpartum in the control group. Assuming 45% protection effect of breastfeeding against postpartum smoking 
relapse,2,26,27 we estimate 25% (45%*[1-45%]) rate of smoking relapse by 6 months postpartum in the 
intervention group. The corresponding sample size is 98 per group with type 1 error α of 0.05 and power 1-β of 
0.8 to detect significant difference in smoking relapse between two groups in the larger R01 project. If 9-month 
postpartum smoking relapse rates (70% control vs 39% intervention) are used, the corresponding sample size 
is 46 per group. Therefore, 30 participants per group for this pilot study should provide sufficient sample size to 
test feasibility and efficacy as well as provide preliminary data regarding mediators and cost-effectiveness. 
 
3.2 Potential Problems & Alternative Strategies. A potential challenge for the proposed project is to recruit a 
sufficient number of pregnant ex-smokers. If significant delay is observed, we will expand recruitment areas, 
use direct mailing, and advertise in local media. Another potential problem is attrition during intervention and 
follow-up periods. We expect 20% attrition rate due to dropouts, losses to follow-up, miscarriages, and fetal 
deaths. If we lose contact, we will reach out to the 3 people that have close relationship with the participant 
indicated at enrollment. We will recruit more participants to ensure sufficient statistical power if attrition is high.  
 
3.3 Timeline of Study Process  
 
MONTH 
TASKS 
2 
4 
6 
8 
10 
12 
14 
16 
18 
20 
22 
24 
IRB approval (before start) 
 
 
 
 
 
 
 
 
 
 
 
 
Hiring and training staff 
X 
 
 
 
 
 
 
 
 
 
 
 
Testing study procedures 
X 
 
 
 
 
 
 
 
 
 
 
 
Surveys and intervention materials 
X 
 
 
 
 
 
 
 
 
 
 
 
Participant recruitment 
X 
X 
X 
X 
X 
X 
X 
 
 
 
 
 
Prenatal breastfeeding intervention 
 
X 
X 
X 
X 
X 
X 
 
 
 
 
 
Postnatal breastfeeding intervention 
 
 
X 
X 
X 
X 
X 
X 
X 
 
 
 
Follow-up (9-month postpartum) 
 
 
 
 
 
X 
X 
X 
X 
X 
X 
X 
Data analysis 
 
 
 
 
X 
X 
X 
X 
X 
X 
X 
X 
Manuscripts & reports 
 
 
 
 
 
 
 
 
 
 
X 
X 
R01 proposal & submission 
 
 
 
 
 
 
 
 
 
 
X 
X 
 
3.4 Future Directions. The preliminary data from this pilot study will support our application of a R01 grant, 
which will extend breastfeeding intervention to 1 year and follow-up to 2 years postpartum. In the larger R01, 
we hope to have the opportunity for multiple measures of oxytocin and prolactin around a feeding episode to 
calculate area under the curve,80,81,85 and testing mediation of other hormones such as progesterone and 
cortisol. We will add cost-effectiveness analysis to evaluate economic impact of intervention. It is also possible 
to scale up our intervention to communities through paraprofessionals (e.g., community health workers105).