The Sucking Efficiency (SEF) is one of the main parameters used to monitor and assess the sucking pattern development in infants. Since Nutritive Sucking (NS) is one of the earliest motor activity performed by infants, its objective monitoring may allow to assess neurological and motor development of newborns. This work proposes a new ecological and low-cost method for SEF monitoring, specifically designed for feeding bottles. The methodology, based on the measure of the hydrostatic pressure exerted by the liquid at the teat base, is presented and experimentally validated at different operative conditions. Results show how the proposed method allows to estimate the minimum volume an infant ingests during a burst of sucks with a relative error within the range of [3-7]% depending on the inclination of the liquid reservoir