Effect of Antenatal Milk Expression on Breastfeeding Outcomes Among Overweight and Obese Women
Phase: NA
Conditions: Breastfeeding
Sponsor: University of Pittsburgh

TITLE: Effect of Antenatal Milk Expression on Breastfeeding Outcomes among Overweight and 
Obese Women 
NCT Number: NCT04258709 
Date of Document: 4/27/2023 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

Recruitment:  
Potential participants may contact us to inquire about participation after learning about the study through 
various advertising strategies we may employ, including: 1) listing the study on the University research 
registry; 2) email advertisement via university email system; 3) study mailers (postal mail) sent to those 
identified via EMR as noted below; 3) study flyers posted in various recruitment locations; 4) advertising 
the study on hospital television monitors around the hospital; 5) advertising through local magazines; 6) 
utilizing study website through the University 7) advertising through social media posts, emails blurbs, 
newsletter blurbs or other communications by community businesses/organizations that serve birthing 
people, parents, infants, children, or families. Participant recruitment materials may also contain a QR 
code for participant ease. This QR code will be linked to a new record in our electronic data capture 
website where potential participants can leave their name and contact information (e.g., email, phone 
number to call or text) to receive more information about the study. We may also initiate contact with 
potential participants who appear to meet basic eligibility criteria according to select fields accessed 
within their electronic medical records. The study PI and study coordinators, who are considered part of 
the hospital-system covered entity by virtue of working under supervision of a co-I, may access the 
prenatal clinic patient lists in EPIC to assess potential patient eligibility (e.g., patients who are at least 18 
years of age, will be coming into the clinic for their 34-36 week appointments, have no other children, 
and meet BMI criteria), with all other screening criteria assessed during screening after permission is 
given to approach/contact patient. Potentially eligible patients identified in this way (through EMR pre-
screening) may then be approached in several ways, depending on clinic and hospital system regulations 
and preferences. 1. Clinical staff members at patients' prenatal provider's office may approach potentially 
eligible mothers at the prenatal visit to gauge interest in talking to study personnel about the study. If 
permission is granted by a mother, study staff may approach potential participant during/after prenatal 
visit to introduce study. Screening and enrollment may occur at the same time or later in-person or 
remotely. 2. Clinical staff or providers may give potentially eligible patients a study brochure and/or 
contact card. Note that clinical staff/providers may identify potentially eligible participants on their own 
or study staff may identify via EMR review and notify clinical staff to provide a patient a brochure/card. 
Interested patients may complete the contact card. Cards will be collected in line with practice guidelines 
(e.g,. left in patient room, returned to nurse, returned to front desk, dropped in a locked study box, etc.). 
Study staff will collect these cards and then contact interested patients via their preferred method to give 
them more information about the study and answer any questions. In lieu of contact cards, clinical 
research staff also may direct potential participants to reach out to study staff (either in-person if located 
at the hospital, or via phone or email). In clinical practices whose standard of care includes giving new 
pregnant patients folders at the time of their first visit, clinical staff may include a study brochure as this 
is a time where patients get many information opportunities including other research studies. Patients 
would then be able to contact study staff if interested and be re-contacted at 34 weeks of pregnancy, with 
their permission, to determine eligibility. 3. We may mail a study advertisement directly to their home 
address as noted in their EMR. The advertisement will include instructions on how to contact the study if 
potential participant is interested in learning more. Study staff may initiate contact/approach beginning at 
28 weeks of gestation (other than the potential of distributing brochures in initial OB folders, which 
would occur as early as patients first prenatal appointment) to introduce the study (basic description, 
provision of study advertising or blank copy of consent form), with screening and enrollment to occur 
later between the 34th and 36th week of gestation. If the potential participant is agreeable, study staff may 
then track her future appointments in EMR and return during a prenatal visit at the clinic between 34-37 
weeks gestation to again assess interest in study and complete screening procedures and enrollment if 
applicable. Alternately, with potential participant's permission, we will keep her contact information and 

re-contact her using her preferred communication method (e.g., phone, text message) between 34-36 
weeks gestation to arrange for in-person or remote screening and enrollment. This additional step of study 
introduction ahead of an enrollment visit may be necessary for some moms to have sufficient time to fully 
consider study participation and plan ahead for the time it would take to complete their enrollment 
procedures and baseline data collection. Note that we may mail study advertisements to potentially 
eligible patients identified through the EMR ahead of 28 weeks. If a patient does not provide consent to 
participate in the study, any protected health information obtained (e.g., maternal age, gestational age), as 
well as contact information, will be anonymized or destroyed.  
Recruitment of prospective participants is detailed in the recruitment section. In all cases, once contact is 
made with a prospective participant, study personnel will provide a brief synopsis of the study, including 
study purpose, study procedures, potential risks and benefits, compensation and right to withdrawal from 
the study at any time without penalty. If interested in participating, study personnel will administer a brief 
screening form to the participant to ensure eligibility criteria are met. If ineligible, the participant will be 
informed of the reason for ineligibility and screening information will be retained without the participant's 
identifiable information (name, birthdate, etc.). If eligible, the research personnel will complete informed 
consent with the maternal participant. This informed consent may be completed in-person on paper, or 
remotely with a member of the research staff via Zoom (or similar platform) with an e-signature. 
Maternal participants will provide permission/consent for their infants to participate in the study, as 
infant-specific data, including background birth information and infant measurements, will be collected 
and the intervention has the potential to affect infant health. In all cases, maternal participants will sign 
and receive a copy (either hard copy or electronic copy) of the informed consent document. Any paper 
original copies will be kept and filed by research personnel. A separate addendum informed consent will 
be obtained to video-record AME sessions for interrater reliability. After informed consent, participants 
will complete baseline study measures/surveys (in-person, over phone or remote video/Zoom, or emailed 
survey; assessing maternal/fetal health, maternal demographics, maternal mood, reproductive history, 
body image concerns, experiences of discrimination, etc; see questionnaires for specifics) and be 
randomized to a group via computer-generated permuted block randomization stratified by pre-pregnancy 
BMI status (overweight: 25-29.9 or obese: ≥30). Subjects will have a 1:1 chance of being randomized to 
either study group, as indicated in the consent document. Study participation will be documented in the 
maternal participant's electronic medical record to alert providers to study participation. Study staff will 
meet remotely or in-person with participants in both groups weekly from 37 to 40 weeks of gestation for 
delivery of the assigned intervention. To maximize participant convenience and safety of all involved 
(given new standards/recommendations around social distancing) study "visits"/contact points will have 
the potential to be conducted completely remotely via a secure video call (e.g., HIPAA-compliant Zoom 
call with screen sharing when needed), audio phone call, or emailed survey. When/if feasible, preferred, 
and safe according to University research standards and current county-level guidance/restrictions, visits 
may also involve in-person meetings between the study participant and study staff (though the 
experimental condition lactation consultants will always deliver the intervention remotely). In-person 
visits may occur at the hospital/clinics before/after a prenatal visit or another mutually agreed upon 
convenient, private place. The details of study visits, according to assigned intervention are detailed 
below. Experimental Condition (AME): With the assistance of study staff, who will facilitate all study 
visits, participants randomized to AME will complete a test video call at enrollment, if possible, with the 
telelactation provider who are available for on-demand, one-on-one visits, 24/7) to increase familiarity 
with the service prior to AME instruction. Note that for subsequent study visits, if for any reason an 
IBCLC is not available, the study may use a substitute remotely-based IBCLC who is trained in study 
procedures. Participants will be taught the AME technique at the 37 week study visit after first viewing an 

introductory video demonstrating the technique. At the visit, study staff will initiate a 3-way 
meeting/connection with an available, remote International Board-Certified Lactation Consultant 
(IBCLC) and the study participant if the visit is remote (e.g., Zoom video call). If the study visit is in-
person, study staff will initiate remote 2-way connection between themselves and study participant with a 
remote IBCLC via a secure video platform (e.g., Zoom). After connecting, the remote IBCLC will 
provide video-based expert instruction and guided feedback on AME and milk collection as the 
participant engages in the technique. Note that IBCLCs are trained in hand-expression as a fundamental 
professional skill and will receive additional training and oversight by study personnel (see intervention 
fidelity below). For participants whose study visits are conducted completely remotely, these meetings 
will occur via a secure HIPAA-compliant platform like Zoom which allows study participant, study staff, 
and IBCLC to see/converse with each other simultaneously. This will require that participants use their 
own electronic device (e.g., smart phone, laptop) for the visit. These meetings will be scheduled a 
convenient time for the participant, IBCLC, and study staff. When a video-based remote connection is not 
possible or problematic (e.g., WiFi issues), study staff will initiate a 3-way audio only phone call instead 
with the IBCLC and participant, and hand expression education will occur over audio to the extent 
possible, with subsequent referral to supplementary streaming videos demonstrating hand expression. As 
per our pilot study protocol, AME will continue for a maximum of 10 minutes during study visits 
(participants will also be advised to do AME for no longer than 10 minutes during their independent 
practice between study sessions). For any in-person study visits, any milk output will be collected into 
study-provided containers and syringes and stored for future analyses as per the protocol outlined below 
(disposition of antenatal milk). During remote sessions, any AME milk that is collected may be labeled as 
milk that may be given to the study, and frozen by the participant. This milk may then be collected and 
aliquoted by study staff at a later date (e.g., no contact porch pick-up of milk at participant's home by 
study staff members). For all AME sessions, additional breastfeeding education will be provided by the 
IBCLC as requested by participant and documented by study staff. Study staff will facilitate the overall 
visit (e.g., introductions, provision of milk collection containers). IBCLCs will reinforce/provide feedback 
on AME technique at each weekly study visit until delivery, with a similar format to the initial visit. 
Around the time of the initial 37 week visit (this may be before or after the visit, dependent on mode of 
AME education delivery), study staff will provide participants oral and written instructions to continue 
AME 1-2 times/day at home until delivery. Instructions (reinforced in weekly visits) will also contain 
information on milk storage, transport to the hospital if participant is storing milk at home, and use; AME 
contraindications; and when and how to seek assistance for any problems (please see attached: brochures 
in "other" documents). Please note that for participants whose visits will occur remotely, members of 
study staff will drop off supplies for AME (e.g., collection containers, labels, syringes, refrigerator boxes 
for transport of milk to hospital) before the first scheduled visit, so that participants have supplies at the 
time of their first session. These will be done in accordance with any county standards in-place at the time 
(i.e., no-contact porch drop-off deliveries, PPE worn if any in-person contact). Compliance with home 
practice, including AME timing, milk volume obtained, and any problems, will be assessed from after the 
first study visit until delivery via daily web-based survey "diaries" (if participant declines web-based 
diaries or there are technical problems with web-based diaries, participants may be provided written 
diaries to be returned to study personnel at a time/place to be arranged, e.g., no contact porch pick up). 
Web-based survey diaries will be administered with an automated SMS notification sent daily to the 
participant with up to 3 reminders through the day to complete. The responses to web-based diaries will 
be automatically recorded in a secure Access study database; if participant completes written diaries, their 
answers will be manually entered in Access database by study staff. With regard to the SMS alert system 
for the web-based diaries, a two-way text messaging system has been built at the University and 
associated hospital for this purpose (as has the survey/diary system itself); the system utilizes a server 

within the hospital system to manage all text message dialogue. The server stores all pre-specified 
libraries of assessment and contingent responses (e.g., automated responses specific to inputted 
information). The server will send queries or messages at specific times and schedules based on pre-
specified study requirements. The server is connected to a modem which conducts all text message traffic. 
All incoming and outgoing text message dialogue is time stamped and recorded, accessible to 
investigators through a MS-Access system front-end. The server also has the capability to send email 
notifications of participant replies to investigators and allows the exchange of non-automated texts 
between participants and investigators. Participant phone numbers are entered into the system in two 
ways: 1. Participants text a specific code word into the modem phone number; 2. An investigator 
manually enters a participant’s phone number into a web-based front end. Intervention Fidelity for 
Telelactation Visits: The study team will work closely with the telelactation clinical leadership to train 
IBCLCs in the standardized delivery of AME education (if other IBCLCs are used, they will also be 
trained in standardized delivery of the intervention). To verify IBCLC adherence to the study’s AME 
teaching protocol, study staff will complete a checklist for each AME study visit (as well as checklists for 
control condition). For the first 20 participants receiving the AME intervention, interrater reliability 
assessment by the PI using the same checklist will occur for every fifth participant (all visits) who either 
1) provides separate, written informed consent for video-recording visits for later review by the PI (in-
person visits only), or 2) is agreeable to having the PI join the live remote session. Thereafter, depending 
on a satisfactory level of adherence to protocol, video reviews or live PI reviews may be decreased to 
every tenth participant for the remainder of the study. If participant visits are in-person, we will make an 
effort to avoid capturing identifiable features of a participant while filming (e.g., face) by aiming the 
camera at the study staff, although it remains possible that a participant may be visible or partially visible 
and their voice audible off-screen. If participant visits are remote, the PI will join the remote call, so that 
no recording takes place, and the study session checklist will be reviewed/marked in real-time. 
Disposition of antenatal milk: Similar to our pilot study, any milk samples collected during in-person 
study visits in pregnancy will be aliquoted, frozen, and stored at the University Biobank for later analyses 
(TBD) with participant permission. Any milk collected during remote study visits may be labeled as milk 
for research study and frozen in participant's home freezers. At participant and study staff convenience, 
this milk can later be given to study staff where it will be thawed, aliquoted, re-frozen, and stored at the 
University biobank for later analyses (TBD). If study staff arrange pick up of milk within 3-5 days of 
expressing, milk may simply be refrigerated by participants until the pick-up day, rather than frozen. 
Antenatal milk collected and stored by mothers at home outside of study sessions will be for use at their 
discretion (e.g., infant supplementation after delivery), and they will be provided with instructions on 
milk home storage, transport to the hospital, and use/provision to the infant. We will collaborate with 
hospital unit leaders at each birthing hospital to notify and educate unit staff who will potentially provide 
care for maternal and neonatal participants (e.g., nurses and providers in prenatal clinics, Labor & 
Delivery, postpartum, NICU) regarding our study and study procedures. A note will be placed in EMR 
alerting all providers to participants’ study participation and potential existence of antenatal milk being 
brought in with participants at time of delivery and/or during postpartum hospital stay. Participants will be 
instructed to alert hospital staff during their birth hospitalization to their study participation and whether 
they have stored milk. Guidelines for safe storage and handling of antenatal milk will be communicated to 
participants, hospital staff, and posted on the refrigerated boxes provided to participants for milk transport 
to hospital.  
Attention Control Condition (video-based infant care education): To stem threats to internal validity 
resulting from unequal attention between groups or lack of “treatment” incentivizing continued study 
participation, study staff will meet with control group participants weekly from 37 to 40 weeks of their 

pregnancy, either remotely or in-person, similar to those in the AME group. In-person visits may occur at 
the hospital/clinics or another private mutually-agreed upon location; remote visits will be via a secure 
remote platform, such as the University’s HIPAA-compliant Zoom. Visits will be approximately 10 
minutes, similar to the intervention group. In this time, participants will view a standard set of web-based 
videos addressing evidence-based infant care, unrelated to feeding/breastfeeding. Videos will focus on a 
different theme each week (e.g., safe sleep, car seat safety, managing crying/colic), downloaded from free 
and reputable patient education sites. If visit is remote, study staff will attempt to "screen share" videos so 
that we may verify that participant actually views/receives the intended education (rather than directing 
participant to view videos on their own). Data Collection and Procedures Unrelated to Intervention 
Delivery: We will collect EMR data regarding maternal pre-pregnancy body mass index (BMI) and 
gestational weight gain, maternal and infant health conditions, labor and delivery information, and 
hospital infant feeding practices from the antenatal and postpartum medical records. Prenatal, 
intrapartum, and postpartum EMR data is housed within the hospital data systems, which the study team 
will access via their research and clinical affiliation with the hospital after IRB approval. In the 
postpartum period, study measures (surveys) assessing breastfeeding practices, perceptions, problems, 
satisfaction, plans, and education/support, as well as maternal mood, birth experience, childcare plans and 
use, and maternal employment (see questionnaires), will be completed by participants in both groups at 
weeks 2, 6, and 12 weeks, and 6 and 12 months postpartum. These measures may be completed remotely 
via emailed survey, in recognition of the time constraints faced by new mothers in scheduling study visits 
and calls. When difficulties are encountered in electronic survey completion, we will call participants or, 
when feasible, meet them during regularly scheduled postpartum clinic visits to complete measures (or at 
another mutually agreed upon time/location). If a participant elects to complete postpartum measurements 
and collection of a milk sample, the survey may be completed in-person at that time, as well. A subset of 
participants will also have included into their Baseline and postpartum surveys questions on sexual 
dysfunction. Please note that this survey is necessarily concurrent with a specific timepoint, and so 
participants who have already completed their participation in the study will not be asked to 
retrospectively complete this survey. In fulfillment of Aim 3, we will conduct individual telephone 
interviews with ≈25% of participants from both groups at 6 weeks postpartum, or earlier if they indicate 
that they discontinued breastfeeding at the 2 week postpartum survey or otherwise notify us at any point 
that they have decided to not start breastfeeding, do not initiate breastfeeding, or stop breastfeeding. We 
anticipate conducting interviews with approximately 70 participants, 35 from each group, selected 
purposively based on variability in AME uptake (e.g., some participants who did not complete any AME, 
some who did it once daily, twice daily, etc.), demographics, and current breastfeeding status to achieve a 
representative group). Interviews will continue until thematic saturation is reached (estimated at ≈25% of 
sample from our prior research). Interviews will address aspects of both AME and the control condition to 
maintain participant blinding to study purpose. Specifically, we will query participants on motivating 
factors for study participation; perceived benefits/utility of AME and antenatal video-based infant 
education; experiences with and evaluation of other breastfeeding and infant education support resources; 
experienced or anticipated burdens/challenges/drawbacks to AME and the control condition; and for AME 
participants, factors/contexts impacting AME uptake and use of antenatal-expressed milk, as well as 
suggested modifications to the AME intervention or study protocol. Interviews will be conducted by a 
qualitative research consultant or study personnel. Interviews will follow a semi-structured interview 
guide, adapted from our current AME pilot RCT, and may be modified as the study progresses based on 
themes raised in prior interviews or issues encountered by study personnel. Interviews are expected to last 
30-45 minutes and will be audio-recorded and transcribed verbatim by QDAP, another secure (e.g., 
HIPAA compliant) transcription service, or study personnel. Both audio files and transcripts will be 
retained electronically without identifying information in accordance with IRB protocols.  

STATISTICAL DESIGN AND POWER  
Sample Size and Power  
The total proposed enrollment of 280 women was determined considering a feasible rate of recruitment, 
expected effect size of the AME intervention on primary outcomes, testing of multiple hypotheses, and 
anticipated rate of attrition and protocol non-adherence at 2 weeks postpartum (primary outcome 
assessment). Our recent intervention research with normal weight and overweight/obese women 
demonstrates medium sized effects (standardized mean difference, d) for the AME intervention at 1-2 
weeks postpartum compared to an education control in terms of higher levels of breastfeeding self-
efficacy (AME: M=52.59, SD=9.92, Education: M=45.71, SD=15.71, d=0.53) and greater percentage of 
breast milk feeds (AME: M=89.50, SD=20.372; Education M=78.64, SD=27.303, d=0.45). Regarding 
exclusive breastfeeding at 1-2 weeks, rates of 0.27 have been reported among overweight/obese 
women.32 With a sample size of at least 210 (105 per group), we can detect with .80 power between-
group differences in the proportions in breastfeeding exclusivity at 2 weeks postpartum as small as .172 
(medium effect size of OR=2.55 using likelihood ratio chi-square statistics) at an adjusted test-wise 
significance level of .0167. While there is a fair amount of heterogeneity in the published effect sizes for 
breastfeeding support interventions among overweight and obese women and for AME specifically, our 
estimate lies in the range of reported effect sizes in the field.12,32 While the examination of long-term 
efficacy of AME is more exploratory (Aim 2), we will be able to detect small to medium interaction 
effects between groups over time as small as f = .323 when using repeated measures F-tests with at least 
four postpartum outcome time points. Our pilot work and previous studies utilizing similar populations 
and recruitment sites indicate that we can conservatively anticipate combined study attrition and 
intervention dropout at ≈25%. To ensure 210 participants with complete follow-up to 2 weeks and no 
protocol deviations, we will enroll 280 women.  
Statistical Methods  
Preliminary Analyses: For Aims 1 and 2, detailed exploratory data analyses will first be performed, 
involving data description and data screening for anomalies (e.g., outliers, nonnormality, etc.). The results 
from this initial investigation will be used to: 1) describe  
univariate and bivariate data distributions; 2) identify imbalances between treatment groups and 
associations between the dependent variables and suspected covariates/confounders; 3) evaluate the 
amount and patterns of missing data; and 4) check for violations of statistical assumptions for the planned 
analyses. If statistical assumptions are seriously violated, data transformations or more statistically robust 
methods will be considered. Covariates/confounders will be included in models secondarily, and their 
impact on the effect of the primary independent variable on the study outcomes will be evaluated. The 
randomness of missing data will be investigated using available information on subject characteristics to 
help discern patterns in the missing data, identify the possible covert missing data mechanisms, and 
inform the choice of the strategies to handle missing data. We will conduct logistic regression models to 
compare the characteristics of participants who remained in the study versus those who dropped out to 
determine if data are missing at random. If data are ignorably missing (i.e., not related to the outcome 
itself), likelihood estimation procedures, such as those in SAS PROC MIXED, GLIMMIX and 
NLMIXED as well as Mplus, will produce unbiased estimates while allowing us to retain cases with 
missing values on the outcome variables. If needed, multiple imputation would be used to impute missing 
values on the predictor variables. If data are not ignorably missing (i.e., non-randomly missing), we may 
use pattern mixture modeling to account for informative attrition.  

Analysis Strategies for Aims 1 and 2: To examine the efficacy of the remotely-delivered AME 
intervention relative to the attention control on breastfeeding outcomes during hospitalization to the first 
two weeks postpartum (short-term; Aim 1) and up to the first 12 months (long-term; Aim 2) among 
overweight and obese (BMI ≥ 25) women, an intent-to-treat (ITT) approach will be used, where all 
participants will be included in analyses as randomized, regardless of protocol adherence/deviations, 
treatment received, or withdrawal. Adherence to the assigned intervention, however, will be monitored, 
and the sensitivity of the results under the ITT model will be explored to identify the effects of the amount 
of intervention received (e.g., number of AME study visits) and deviations in protocol on outcomes.  
The primary outcome variables of interest for the short-term efficacy of the AME intervention at 2 weeks 
postpartum (Aim 1) are 1) proportion of mothers providing 100% breast milk, 2) percentage of feedings 
that were breast milk, and 3) breastfeeding self-efficacy. Secondary breastfeeding outcomes for short-term 
efficacy include proportion of mothers with any breastfeeding, perceived milk supply, onset and days to 
lactogenesis II, and days to any formula and/or breastfeeding cessation. Secondary long-term efficacy 
outcomes (Aim 2), which will be assessed at all follow-up points until 12 months postpartum (or 
breastfeeding cessation/loss to follow-up), are duration of breastfeeding in days and any breastfeeding at 
postpartum follow-ups; the continuous and categorical type versions of breastfeeding exclusivity; and the 
proximal intervening outcomes (i.e., mediating variables) including the repeatedly measured 
breastfeeding self-efficacy and perceived milk supply.  
Generalized linear mixed-effects modeling with linear contrasts will be used to examine the effect of 
treatment assignment (AME vs. attention control) for each repeatedly assessed outcome, with treatment 
group assignment as the between-subjects factor, time as the within-subjects factor, and an interaction 
between time and treatment group. Given the level of measurement and observed data distribution of the 
particular dependent variable, an appropriate error structure and link function to the linear predictors will 
be assumed. For example, for breastfeeding exclusivity and any breast feeding, each assessed as a binary 
variable, a binomial error structure will be assumed and a logit link to the predictors will be applied, while 
for the continuous type versions of breastfeeding exclusivity and the interval-scaled breastfeeding self-
efficacy, a normal error  
distribution will be considered with an identity link to the linear predictors. Random effects for 
participants will also be included. Fixed and/or time-dependent covariates (e.g., pre-pregnancy BMI 
category [25.0-29.9; 3034.9; 35-39.9; 40+]) may be included secondarily to adjust for group imbalances 
or variables related to the dependent variables based on the literature or data screening results. Standard 
fit criteria (e.g., AIC and BIC) also will be used to identify the best-fitting repeated measures covariance 
structure. F-tests will test the main and interaction effects included in the model. Individual regression 
parameters will be estimated with confidence intervals. For each model, residual analyses will be 
conducted to identify sources of model misspecification, outliers, and influential observations. Sensitivity 
analyses will be performed to discern the impact of influential cases on modeling results. Linear contrasts 
will be specified in the repeated measures models to test whether the AME intervention demonstrates 
greater improvements in breastfeeding outcomes compared to the attention control at each time point, in 
particular, when conducting hypothesis testing on the primary short-term outcomes. Point and interval 
estimates will be obtained for each of the comparisons examined.  
For event history type outcomes (e.g., breastfeeding duration, days to the onset of lactogenesis II, days to 
any formula) Cox proportional hazards regression methods will be applied to allow for possible censoring 
of the event of interest and inclusion of the fixed and time-dependent predictors. For summary outcomes 
(e.g., proportion of breast milk in-hospital), generalized linear modeling will be applied.  

To explore possible moderators of the treatment efficacy of the AME intervention relative to the attention 
control, the generalized linear models for summary breastfeeding outcomes and the generalized linear 
mixed models for repeatedly assessed breastfeeding outcomes will be expanded to include the potentially 
moderating variable and its interactions with the other model terms (treatment group, time, treatment 
group by time). To explore possible mediation by the identified proximal/intervening variables (e.g., 
breastfeeding self-efficacy), mediational models will be fitted using structural equation modeling to allow 
for repeatedly assessed and censored proximal and distal outcomes, considering partial mediation and full 
mediation with no direct effects. From these analyses, path coefficients with confidence intervals will be 
obtained.  
Analysis Strategy for Aim 3: We will undertake a qualitative analysis for Aim 3 (perceptions of and 
experiences with AME), described within the Research Strategy. We will also descriptively analyze 
characteristics of participants who participate in these interviews for reporting purposes.