Gender of participants was not explicitly assessed in this study. Thus, gender inclusive terms are used throughout to account for participants in this study who may not have identified as a “woman” or “mother.” When describing infant feeding, we also attempt to use the most specific, gender inclusive descriptors. Sometimes this was precluded, as surveys options were designed with gendered or non-specific terms (e.g., “breast milk” vs. “my own milk”). When referencing others’ research or work, we use their stated terminology.
Design
In this pilot randomized controlled trial, we recruited nulliparous people in their third pregnancy trimester and used sealed envelope block randomization to assign them to a structured AME intervention or an education control. Participants completed an enrollment/baseline study visit between 340/7 and 366/7 weeks of pregnancy. Study visits to deliver the assigned intervention were scheduled weekly from 37 to 406/7 weeks of pregnancy or until the infant’s birth, whichever occurred first (maximum of four visits in pregnancy). Visits were scheduled based on participant preference—often immediately following a prenatal visit in a clinical research suite adjacent to the prenatal practice. In the postpartum period, we met with participants to administer surveys during the birth hospitalization (1–4 days postpartum), at 1–2 weeks postpartum, and 3–4 months postpartum. Measured outcomes of interest at postpartum follow-ups included breastfeeding self-efficacy, perceived milk supply, perceived onset of lactogenesis II (copious milk production), and infant feeding status/formula use. No formal sample size estimation in terms of testing hypotheses was conducted; instead, the target sample size (n = 45) was based on a predefined timeframe and budget that would generate feasibility data for a larger trial. Participants were compensated up to $50 for their participation, based on number of study visits completed.
Participants and setting
We recruited participants between December 2016 and February 2018 from a hospital-based midwife practice at UPMC Magee-Womens Hospital (Pittsburgh, Pennsylvania). Our primary recruitment strategy was electronic health record review of select eligibility criteria (parity, gestational age), followed by in-person approach of potentially eligible patients at a prenatal visit between 34 and 366/7 weeks of pregnancy to assess interest in study participation. Study flyers with contact information were also posted in the midwife office for patient self-referral.
Interested patients were screened for full eligibility, provided written informed consent, and randomized prior to completing baseline study measures. Eligible participants were at least 18 years old, nulliparous, pregnant with a single fetus, planned to exclusively breastfeed/provide their own milk to their infant for the first four months postpartum, did not have any known physiologic risk factors for insufficient milk supply (e.g., breast hypoplasia, polycystic ovarian syndrome, diabetes, breast reduction surgery), and did not have any conditions constituting a high-risk pregnancy (e.g., vaginal bleeding after the first trimester, fetal congenital anomalies, polyhydramnios, current smoking) [22].
AME intervention
At an introductory visit to AME during week 37 of pregnancy, participants viewed a video modeling hand-expression of milk [23]. This video exemplar was chosen because it featured close-up footage of a model self-expressing milk using similar techniques advised by the study IBCLC during participant individual instruction (e.g., breast massage prior to and during expression, “c” or “u” shape finger placement back from the nipple, 3-step Marmet technique [24], rhythmic pace while alternating between breasts). Because the model in the video was several days postpartum, participants were cautioned that the volume and appearance of any milk expressed would likely differ.
Following the video, participants were invited to engage in hands-on, guided practice of AME beginning with breast massage and utilizing the Marmet technique [24] with an International Board Certified Lactation Consultant (IBCLC; author JRD). After instruction/practice at the initial visit, we provided participants written and verbal instructions for safe expression, collection, and storage of antenatal milk in the home setting. At subsequent weekly study visits during pregnancy, participants met with the lactation consultant to reinforce AME technique, address questions about AME or breastfeeding, and collect a milk sample if possible for later analyses of macronutrient and immunological composition of antenatal milk (milk samples were also collected from participants in both groups at each postpartum follow-up for comparison). Similar to the protocol for home milk expression described by Forster and colleagues [25], participants were instructed to engage in at-home milk expression and collection one to two times per day for up to ten minutes and record this in a written diary, which was collected at subsequent study visits. Participants were provided sterile, flip-top containers (11 mL Snappies® colostrum collectors) in which to collect and freeze antenatal milk and instructions on how to transport and store antenatal milk at the birth hospital.
Education control
Participants in the education control group met with study staff during study visits in pregnancy to receive handouts from Lactation Education Resources [26]. Handouts addressed a new theme each week pertaining to breastfeeding preparation and prevention of common lactation problems (Week 37: “Sore Nipples”; Week 38: “Five Keys to Successful Breastfeeding”; Week 39: “Signs of a Good Feeding” and “Is my Baby Getting Enough?”; Week 40: “I wish someone had told me …”). Control group participants did not receive any education on AME or additional lactation education from study staff. Handouts did not address AME. The rationale for offering handouts to the control group was to provide contact episodes with study staff similar in frequency to the AME group and to minimize attrition by offering an educational incentive.
Participants assigned to AME were not provided the hand-outs that the control group received. Participants in both groups may have received lactation education outside of the study, as we did limit or replace any education offered by the prenatal practice, other care providers, or community-based resources.
Data collection and measurement
At enrollment, participants completed a survey assessing demographics, obstetric and medical history, and breastfeeding attitude (Iowa Infant Feeding Attitude Scale; score range 17–85, with higher scores indicative of more favorable attitude toward breastfeeding) [27]. Breastfeeding intentions/plans were assessed at enrollment with two questions, “After your baby is born, how long do you plan to exclusively breastfeed (i.e., feed baby ONLY breast milk with no formula or other foods)?” and “ After your baby is born, how long do you plan to continue ANY breastfeeding or breast milk feeds?”. Both questions were multiple choice with by-month groupings (e.g., < 6 months) and an “unsure” option.
At enrollment and postpartum visits, surveys included an assessment of prenatal and postpartum breastfeeding self-efficacy, respectively (Breastfeeding Self-Efficacy Scale-SF; score range 14–70 with higher scores indicative of higher self-efficacy) [28, 29]. At enrollment and postpartum visits, we also administered a combined measure of stress, anxiety, and depression, as important correlates of lactation outcomes (Perceived Stress Scale-4 [30], PROMIS Emotional Distress-Anxiety 4-item bank [31], 3-item Pregnancy Risk Assessment Monitoring System (PRAMS) Depression/Anxiety [32]; score range 11–55 with higher scores indicative of higher levels of anxiety, stress, and depressive symptoms).
In a daily written diary, participants in the AME group tracked number and duration of daily home AME sessions, approximate volume of AME milk collected via visual estimation (using 5 mL line on container), and any problems experienced with AME. The latter was assessed via open-ended questions, “Any cramping or side effects during or after expressing?” and “Additional comments?”. At each study visit for AME participants, we recorded volume of milk expressed, problems experienced during AME at that particular visit and as verbalized by the participant (checklist of common concerns/issues previously reported about AME [33] and a free-text field), and whether the participant had experienced any of the following during or directly after AME since the prior study visit: prolonged uterine tightening lasting longer than 1 min, frequent uterine tightening (> 5 times in 10 min), vaginal bleeding, or reduced fetal movement.
We collected infant feeding data from the electronic health record (EHR) during the birth hospitalization, including initiation of direct chest/breastfeeding (any and timing post-birth), and receipt and total volume of expressed milk and infant formula. Additional data collected from the EHR included pregnancy complications and characteristics of the labor and birth. Data were abstracted independently by two researchers and any discrepancies resolved through re-review of EHR data and discussion with the first author.
Postpartum surveys assessed perception of insufficient milk using two methods: 1) a single investigator-created item asking “Do you feel you make enough breast milk to satisfy your baby?” with answer options of “yes,” “no,” or “unsure” (dichotomized for analysis to yes = “no perceived insufficient milk” and no/unsure = “perceived insufficient milk”); and 2) score on the Perceived Infant Breastfeeding Satiety subscale (5 items total) within the H&H Lactation Scale [34]; possible scores ranged from 0–35, wherein lower scores represent lower confidence that one is making enough milk. Infant Satiety subscale scores at one week postpartum have demonstrated predictive validity with breastfeeding continuation at eight weeks. The subscale also exhibited concurrent validity with perception of insufficient milk at eight weeks [34].
Postpartum surveys also assessed current infant feeding status with the following survey item: “How are you currently feeding your baby?” Answer options included “breast milk only,” “formula only,” and “both formula and breast milk.” While it was unlikely that any study infants were receiving pasteurized donor human milk (based on eligibility criteria within the health system), it is a possibility that infants were receiving milk from another lactating parent (i.e., informally shared milk).
Whether any antenatally-expressed milk had been fed to the infant was assessed in each postpartum survey with a dichotomous survey item: “Since your baby was born, have you given him/her any milk that was hand-expressed while you were still pregnant?”. A follow-up free-text item asked participants to estimate the total volume of antenatal milk in milliliters that they had fed to their infant since birth.
The 1–2 week postpartum survey assessed onset of lactogenesis II in days postpartum by asking, “How long did it take for your milk to come in after your baby was born (i.e., when did you notice a big increase in the amount of milk)?”, with the following answer options: 1 day or less, 2 days, 3 days, 4 days, more than 4 days, my milk never came in, and I don't remember when my milk came in. Answer options were then collapsed to < 4 days (normal onset) or ≥ 4 days (delayed onset), which corresponds with research indicating an average onset of lactogenesis II between 50–73 h, with delayed lactogenesis typically classified as > 72 h postpartum [35, 36]. No participants selected that their milk never came in. One participant did not remember when their milk came in and was not included in descriptive statistics for this variable. The language of the question was adapted from a validated two-question assessment of lactogenesis II based on maternal perception, which demonstrated high sensitivity and specificity for detecting delayed lactogenesis II compared to the gold standard of infant test weights [37]. However, the validated assessment queried postpartum individuals three times daily, beginning at 24-h postpartum and recorded responses to the nearest hour. Our adaptation to timing the assessment at 1–2 weeks postpartum was intended to minimize cumulative participant survey burden in the postpartum period. In addition, our answer options were adapted from a by-hour recall to a by-day recall, based anticipated difficulty for participants in recalling details at 1–2 weeks postpartum.
Qualitative interviews were conducted with participants assigned to AME to explore their study experiences and assess acceptability of the intervention. Those results are published elsewhere [19].
Analysis
Feasibility of recruitment and retention was assessed via screen-to-consent ratios, attrition rates, and incidence of unintentional intervention cross-over. We calculated descriptive statistics for sample characteristics, uptake of the AME intervention (frequency of expressing episodes, completion of study visits), problems with AME, and lactation and perinatal health outcomes using SPSS v. 27 (IBM Corporation, 2020).