Feeding by sucking is one of the first activities of daily life performed by infants. Sucking plays a fundamental role in neurological development and may be considered a good early predictor of neuromotor development. In this paper, a new method for ecological assessment of infants' nutritive sucking behavior is presented and experimentally validated. Preliminary data on healthy newborn subjects are first acquired to define the main technical specifications of a novel instrumented device. This device is designed to be easily integrated in a commercially available feeding bottle, allowing clinical method development for screening large numbers of subjects. The new approach proposed allows: 1) accurate measurement of intra-oral pressure for neuromotor control analysis and 2) estimation of milk volume delivered to the mouth within variation between estimated and reference volumes.