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Table 2 Covariates/moderating variables and measurement

From: Effect of antenatal milk expression education on lactation outcomes in birthing people with pre-pregnancy body mass index ≥25: protocol for a randomized, controlled trial

Variable

Measurement

Source

Assessment timing

Intervention receipt/dose

Number of AME study visits and home-AME sessions

Investigator study tracking system, SMS queries

Daily from 37 wk. visit to birth

Antenatal milk volume

Total volume of antenatal milk expressed during study and average volume per AME session, in milliliters

SMS queries

Daily/weekly from 37 wks to birth

Demographic characteristics

Age, race, ethnicity, gender, Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), education, employment, relationship status, size of household

IFPS-II adapted and investigator-created items

Enrollment

Breastfeeding attitudes and intentions/plans

Sum scale score measuring extent of agreement with statements about breastfeeding attitudes on Likert scale; sum scale score measuring extent of agreement with statements about breastfeeding duration and exclusivity on Likert scale; anticipated infant age of formula/ other foods introduction and stopping breast milk feeds

Iowa Infant Feeding Attitude Scale (13 items) [57]; Infant Feeding Intentions Scale (3 items)a [58]; IFPS-II adapted items

Enrollment

Prior breastfeeding exposures, inter-generational effects

Whether participant and partner were breastfed (yes/no), proportion of friends/relatives that breastfed, perceived importance of others’ feeding opinions on Likert-scale

IFPS-II adapted items

Enrollment

Birth characteristics and birth center course

Birth mode, anesthesia, neonatal intensive care unit admission, infant birthweight, length of birth center admittance

Birth center EHR abstraction

Birth center admittance

Participant and infant health status

Various chronic, pregnancy, birth associated morbidities checklist

Prenatal and birth center EHR abstraction, investigator-created survey items

Enrollment and birth center admittance

Participant weight

Pre-pregnancy body mass index, gestational weight gain

Prenatal and birth center EHR abstraction

Enrollment and birth center admittance

Anxiety and depression

Frequency of feelings or thoughts

Perceived Stress Scale (4 items) [59]; PRAMS anxiety-depression (3 items) [60]

Enrollment, PP wks 2, 6, 12; 6 & 12 mos

Breastfeeding practices in birth center and home and milk expression details

Timing of first direct breastfeed, average LATCH score at birth center [61], number of lactation consults, number of direct breastfeeds and expressed milk feeds 24 hours prior to birth center discharge; mode of own milk feeds, frequency and methods used to express and feed one’s own milk

Birth center EHR abstraction, IFPS-II adapted and investigator-created items

Birth center admittance and PP wks 2, 6, 12; 6 & 12 mos

Breastfeeding support and education

Checklist of support from various resources, workplace breastfeeding support checklist, extent of agreement about support quality

IFPS-II adapted and investigator-created items, Breastfeeding Friendly Worksites Scorecard adapted items [62]

Enrollment, PP wks 2, 6, 12

Breastfeeding problems

Checklists of breastfeeding problems, reasons for formula use, reasons for breastfeeding cessation

IFPS-II adapted items

PP wks 2, 6, 12; 6 & 12 mos

Breastfeeding satisfaction

Extent of agreement with statements about breastfeeding

MIBSS subscale of H&H Lactation Scale (5 items) [33]

PP wks 2, 6, 12

Embodied weight stigma

Subscale score of instrument assessing frequency of body image psychological discomfort, shame

Weight- and Body-Related

Shame and Guilt Scale (WEB–SG), Shame subscale (6 items) [63]

Enrollment

Traumatic birth experiences

Sum scale of Likert-scale instrument assessing stress, fear, and partner support surrounding birth

Birth Experiences Questionnaire (10 items) [64]

2 wk

Racial discrimination

Sum scale of instrument assessing frequency of perceived racial discrimination experiences

Everyday Discrimination Scale (9-item) [65]

Enrollment

  1. EHR electronic health record, PP postpartum, wk.(s) week(s)
  2. aOnly items 3–5 included from Infant Feeding Intentions Scale, as items 1–2 part of study eligibility (score range 0–12, with higher score indicative of stronger intention to exclusively breastfeed up to 6 months postpartum)