Integrating Ultrasound Biomechanics and Clinical Assessments to Examine Breastfeeding Function: Novel Insights into Tongue Mobility, Milk Transfer, and Reflux Symptoms

Background Breastfeeding is a dynamic co-occupation between mother and infant, influenced by both anatomical and functional factors. Tongue mobility plays a critical role and may impact maternal nipple pain, as well as infant feeding efficiency and quality. Breastfeeding biomechanics, evaluated using tools such as ultrasound, and clinical aspects, assessed through questionnaires and examinations, have largely been studied independently. The aim of this study was to explore correlations between gastroesophageal reflux symptoms, milk transfer rate, and both established and novel ultrasound-based measurements. Methods A prospective cross-sectional study was conducted including 21 mother-infant dyads (infants aged 3–6 weeks). Data collection included demographic questionnaires, clinical assessments of tongue mobility and breastfeeding self-efficacy, as well as real-time ultrasound imaging of the tongue and nipple during feeding. Milk transfer rate was measured by pre- and post-feed infant weight. Statistical analyses included Mann-Whitney tests, Spearman’s correlations, and linear regression to explore associations between clinical and biomechanical parameters. Results Milk transfer rate was significantly associated with ultrasound measurements, including tongue-nipple distances and angles, and maternal nipple pain scores (r in the range 0.49–0.59, and 0.029 − 0.012 respectively). Significant predictors for milk transfer rate were pain at attachment and the angle between the Hard Soft Palate Junction (HSPJ) and the nipple in the Tongue Up (TU) position, together explaining 58.2% of the variance (p = 0.002). A transfer rate threshold of 4.5 g/min demarcated qualitative changes in the ultrasound measurements. Higher pain scores and restricted tongue mobility correlated with lower milk transfer rates (ranges of r = 0.509–0.558, p = 0.02–0.036). Gastroesophageal reflux symptoms were negatively correlated with nipple diameter changes during feeding (r=-0.6, p = 0.009). Pacifier use was associated with reduced tongue lateralization (r=-0.589, p = 0.006). Conclusions This study highlights the interplay between breastfeeding biomechanics and clinical symptoms. Milk transfer rate emerged as an indicator of breastfeeding efficiency, influenced by both maternal and infant factors. These findings suggest a potential mechanistic link between feeding quality and the presence of gastroesophageal reflux symptoms. Incorporating time-based milk transfer assessments and ultrasound measurements into clinical practice may enhance diagnostic precision and therapeutic strategies. Clinicians are encouraged to assess breastfeeding quality in cases of reflux symptoms and provide targeted interventions for pacifier users to improve tongue mobility when necessary.