BackgroundWhether infants use suction or peristaltic tongue movements or a combination to extract milk during breast-feeding is controversial. The aims of this pilot study were 1] to evaluate the feasibility of using 3D ultrasound scanning to visualise infant tongue movements; and 2] to ascertain whether peristaltic tongue movements could be demonstrated during breast-feeding. Methods15 healthy term infants, aged 2weeks to 4months were scanned during breast-feeding, using a real-time 3D ultrasound system, with a 7MHz transducer placed sub-mentally. Results1] The method proved feasible, with 72% of bi-plane datasets and 56% of real-time 3D datasets providing adequate coverage [>75%] of the infant tongue. 2] Peristaltic tongue movement was observed in 13 of 15 infants [83%] from real-time or reformatted truly mid-sagittal views under 3D guidance. ConclusionsThis is the first study to demonstrate the feasibility of using 3D ultrasound to visualise infant tongue movements during breast-feeding. Peristaltic infant tongue movement was present in the majority of infants when the image plane was truly mid-sagittal but was not apparent if the image was slightly off the mid-sagittal plane. This should be considered in studies investigating the relative importance of vacuum and peristalsis for milk transfer.