Effect of Incentives for Self-weighing, Weight Management Goals and Physical Activity Goals on Gaining Weight Healthily During Pregnancy
Phase: NA
Conditions: Gestational Weight Gain
Sponsor: University of Tennessee

Bloom Research Study 
 
Protocol and Analysis Plan (Approved by the University of Tennessee Health Science’s 
Institutional Review Board on 6/18/2019) 
 
ClinicalTrials.gov NCT03834194 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

1. Purpose  
To study the impact of different incentive stuctures and weight management practices (i.e. self-
weighing, weight goal setting, exercise goal setting) on gestational weight gain management. 
  
2. Rationale 
Gestational weight gain (GWG) is a serious public health concern, and 37% of normal weight, 
64% of overweight, and 49-64% of obese women exceed the Institute of Medicine’s GWG 
guidelines. Research has found that modest financial incentives are a promising pragmatic 
strategy for a GWG intervention. Yet, most previous weight management research that has 
utilized incentives has targeted weight outcomes rather than the behaviors necessary to 
achieve them. This study to examine the impact of frequent chances to win small, proximal 
incentives for meeting short-term goals of monthly self-weighing and larger incentives for 
meeting overall GWG goals by the end of the 36-week gestational period. 
  
3. Study/Project Population  
There will be 50 mother and baby pairs (N=100) included to account for screening failures but 
only 40 of those pairs (N=80) randomize. Pregnant participants (N=100) in their first trimester 
at an OB-GYN Specialists clinic in Memphis, TN will be randomized in a fractional factorial 
experiment. Participants must be at least 18 years old and be less than 12 weeks gestation 
upon recruitment (based on the date of their last menstrual period and then confirmed by their 
physician at their first prenatal visit), as interventions that begin prior to gestational week 12 
are more effective. 
  
4. Research Design 
Potential participants will be identified by the clinics’ health professionals (i.e., nurses, 
obstetricians) at their pregnancy confirmation visit or will be self-identified through recruitment 
materials posted in the obstetric clinic (e.g., exam rooms, lobby and bathrooms). They will 
encouraged to contact the study team if they wish to learn more about the study and 
potentially enroll in the study. Interested individuals will be evaluated for the eligibility criteria 
(see above) and written informed consent will be obtained. 
  
Upon recruitment, individuals who are interested in learning more about the study will be 
directed to the Way to Health web portal. Upon reaching the portal, potential participants will 
be asked to create an account and will then be informed of the details of the study, including its 
objectives, duration, requirements, and financial payments. If participants are still interested in 
participating, the Way to Health portal will take them through an automated online informed 
consent. The consent document will be divided into sections and potential participants will 
have to click a button to advance through each section. This is to help ensure that participants 
read the consent form thoroughly by breaking down the form into manageable blocks of text. 
Successive screens will explain the voluntary nature of the study, the risks and benefits of 
participation, alternatives to participation, and that participants can withdraw from the study at 
any time. On the final consent screen, potential participants who click a clearly delineated 
button stating that they agree to participate in the study will be considered to have consented 
to enroll. After consenting, participants will complete an online questionnaire to determine 

their eligibility (i.e. whether participants are 18 years or older, whether they are no more than 
12 weeks pregnant, and whether they have wireless internet or a Bluetooth connected device). 
Eligible participants will first answer a few questions about the number of pregnancies they 
have prior to the current one, age, annual household income, marital status, employment 
status, household size, education level, race, and ethnicity. Then, they will be randomized to 
one of the study arms and led through an automated description of the details specific to that 
arm. Participants will be provided with details regarding how to contact the research team via 
email or phone at any time if they subsequently wish to withdraw from the study. This contact 
information will remain easily accessible via the participants’ individual Way to Health web 
portal dashboards throughout the study. 
  
Participants (N = 40) will be randomized to one of 8 conditions , with combinations of 3 
different components of incentive for GWG management and physical activity. Assessments will 
be conducted at baseline (i.e., in the first trimester), 32 weeks gestation and 36 weeks 
gestation (if the participant has not yet delivered) and will include measures of body weight and 
treatment satisfaction. Participants will be asked to complete daily weigh-ins using the scale 
provided by the study, as well as wear a physical activity tracker (i.e. Fitbit). 
 
Self-Weighing (Lottery) 
Participants randomized to an arm that contains the self-weighing (lottery) component will be 
asked to pick a number between 00 and 99 at randomization, and will be informed that there 
will be a daily lottery, for which they will be eligible if they have weighed themselves in the 
previous day on the Withings e-scale. Then, for each day of their pregnancy, participants will be 
informed of the study’s randomly-generated winning lottery number. Participants who weighed 
themselves the previous day with a one- or two-digit match will be also specifically notified of 
their reward. A two-digit match (1 in 100 chance) will yield a $15 incentive and a single-digit 
match (1 in 5 chance; that is, if the participant’s lottery number is 27, an example of a one-digit 
match is 77) will yield a $2 incentive. A maximum of $112 could be earned over the pregnancy. 
Participants will receive their weekly winnings from weigh-in on Mondays of the following 
week. 
  
Self-Weighing (Certain Loss) 
Participants randomized to an arm that contains the self-weighing (certain loss) component will 
have a balance shown at the beginning of the study on the participant dashboard and each day 
that they do not weigh, $0.50 will be subtracted from this account. The beginning balance will 
be based on the number of days until 36 weeks gestation for each participant, which will vary 
slightly due to when participants enroll in the study. Participants will receive their weekly 
payout (a maximum of $3.50 for 7 days) from weigh-in on Mondays of the following week. A 
maximum of $112 could be earned over the pregnancy. 
  
Monthly GWG component 
Participants randomized to an arm that contains the monthly GWG incentive component will 
receive $14 per month if they have gained within the recommended monthly range for their 
BMI category (Table 2). “Ineligible for incentive” participants will be specifically notified that 

they would have received $14 had they had gained within the recommended range for the 
month, drawing on research showing that loss aversion can be motivating. Participants will 
receive their monthly balance on the first weekday of the following month. A maximum of $112 
could be earned over the pregnancy. 
 
 
 
Overall GWG component 
Participants randomized to an arm that contains the overall GWG incentive component will be 
given the Institute of Medicine gestational weight gain recommendation based on their body 
mass index at randomization, adjusted for data collection at 36 weeks (Table 3). If they achieve 
the goal at 36 weeks, they will receive $112 after the data collection visit. 
  
Table 3. Overall weight gain goals by weight status (adjusted goals based on data collection at 
36 weeks gestation) 
  
 
  
Weekly physical activity 
Participants randomized to an arm that contains the physical activity component will be ask to 
achieve a 150 minute physical activity goal for each week based on the guideline from the 
American College of Obstetricians and Gynecologists (ACOG), 21 and they will receive $3.50 if 
they meet their activity goal for the week. Participants who do not meet the activity goal will be 
notified that they would have received $3.50 had they meet their activity goal, drawing on 
research showing that loss aversion can be motivating. Participants will receive their weekly 
payout on Mondays of the following week. 
 
The total amount that any one participant can earn through the incentives is $336. 
  
Measures will be obtained by trained research staff who are blinded to treatment assignment 
and who will be located within the obstetric clinic. Baseline measures will be obtained just prior 

to randomization. In-person follow-up data collection visits will be scheduled at gestational 
week 32 and week 36. Incentives ($30 for each follow-up visit) will be used to obtain high 
retention at all follow-up data collection visits. In addition, the research staff will attempt to 
schedule the data collection visits before or after regular office visits, in order to facilitate 
retention. 
  
5. Study/Project Procedures  
a. recruitment  
b. randomization into study arms  
c. participants receive feedback about whether their numbers were drawn in the lottery and 
whether they won the incentive pending weight management results  
d. study team analyzes whether different incentive structure affects participants' gestational 
weight gain  
  
6. Outcome Measures  
 
Intervention Satisfaction: At 32 weeks gestation, participants will be asked to offer insight into 
program acceptability in each condition, as well as satisfaction to the program in general. We 
will examine feedback on specific intervention aspects, which will inform program refinement 
and future implementation. 
 
Recruitment yields observed from enrollment survey: The number of participants initially 
recruited for the study will be closely monitored. 
 
Program retention observed from enrollment and follow-up surveys: The number of 
participants stayed in the study within the time frame of the study will be closely monitored. 
 
Gestational Weight Gain (i.e., baseline to final prenatal visit): At all measurement visits, weight 
will be recorded in kilograms on a calibrated research-grade scale. Weight will be measured on 
a calibrated digital scale in duplicate, with the participant wearing light clothing and no shoes. 
While we will obtain the mother’s weight at baseline, we will also obtain self-reported 
preconception weight (before the last menstrual period). We will calculate the participant’s 
GWG goal based on self-reported preconception BMI. Strong concordance between self-
reported preconception weight and measured pregravid weight has been demonstrated. 22 
The difficulty of anticipating when a final weight should be obtained to capture the fullest 
extent of GWG was considered, and we elected to use an approach that afforded two possible 
weights that would be available for analytic purposes. The Week 36 weight will be the primary 
outcome except for mothers who deliver prior to 36 weeks, in which case we will use the Week 
32 weight. Thus, we will have a final observation of GWG for all participants, regardless of 
whether they deliver earlier than 36 weeks. However, only approximately 11% of pregnant 
women have their child before 37 weeks; 23 thus, we expect that we will be able to collect 
Week 36 data on most participants. 
  
Other Measures 

Height: Height will be recorded in centimeters. 
  
Demographics:  Participants will complete a questionnaire regarding their age, annual 
household income, marital status, employment status, education level, race, and ethnicity. 
  
Weight Self-Monitoring: We will electronically monitor daily self-weighing as a measure of 
treatment engagement (coded each day as present or absent). 
  
Physical Activity: We will electronically monitor participants’ weekly physical activity as a 
measure of treatment engagement (measured in active minutes). 
 
Analysis Plan 
 
This is a feasibility study, the primary purpose of which is to gather data that would evaluate 
the feasibility of recruitment, randomization, and retention, as well as treatment engagement 
and intervention satisfaction. An additional aim of this study is to pilot the intervention 
components, consistent with the preparatory stage of the multiphase optimization strategy 
framework. The trial was not powered to detect a significant difference among the conditions 
on treatment engagement or GWG. 
 
We will describe characteristics of the sample using counts and percentages for categorical data 
and means and SDs for continuous data. All analyses will be implemented using R (version 
4.0.2; The R Foundation for Statistical Computing).