A Pilot Feasibility Randomized Controlled Trial of Effects of Opaque Bottles on Maternal Sensitivity, Infant Intake, and Infant Weight Status

Background Conventional clear infant feeding bottles provide visual cues about the amount of milk consumed, which may decrease caregivers’ sensitivity to infant cues, increase infant intake, and lead to greater infant weight gain. Objective This study examined feasibility, adherence, acceptability, and preliminary effectiveness of an intervention wherein families received clear versus opaque bottles. Design A pilot feasibility randomized controlled trial was conducted. Participants /Setting: Participants included mothers (N = 76) with young infants (2.9 ± 1.4 months old). Data collection occurred between December 2018 and July 2022 and within San Luis Obispo and Santa Barbara Counties, California. All assessments occurred within participants’ homes. Intervention Participants were randomized to use clear (Clear group, n = 38) or opaque bottles (Opaque group, n = 38) for 12 weeks. Main Outcome Measures We assessed feasibility of recruitment and retention, participant perceptions of study bottles, participant adherence to the intervention, maternal sensitivity to cues, infant intake (ml and ml/kg), and infant weight-for-length z-scores (WLZ). Statistical Analyses Performed Data were analyzed using linear regression, chi-square analysis, and repeated measures analysis of variance (ANOVA). Results Of 842 potential participants, 295 (35%) could not be reached after initial contact, 166 (20%) declined to participate, and 305 (36%) were ineligible. Of those who declined, 16 (10%) declined because they did not want to use study bottles. No differences were observed for loss to follow-up for Clear (8 of 38, 21%) versus Opaque (5 of 38, 13%) groups (p = 0.36) or for reported use of assigned bottles for Clear (89.8% ± 24.5% of daily feedings) versus Opaque (90.1% ± 22.1%) groups (p = 0.96). No group differences were observed for sensitivity to cues (p = 0.52) or intake (ml, p = 0.53 or ml/kg, p = 0.56) at follow-up. Opaque group infants had lower WLZ at follow-up compared to Clear group infants (mean difference, 0.47; 95% confidence interval, 0.08, 0.86; ηp2 = 0.17), adjusting for baseline WLZ. Conclusions Relative to providing clear bottles, providing families with opaque bottles appeared feasible and acceptable with good adherence. Although preliminary, study findings suggest the potential of opaque bottles to support healthier weight outcomes for bottle-fed infants.