The objective of the present study was to elucidate the anatomical features of the structure of the middle ear and eustachian tube in the breast-fed infants of different gestational age that may be responsible for the formation of exudates (fluids). We have examined 150 temporal bones obtained from the children’s cadavers that were allocated to three groups as follows: 50 temporal bones obtained at weeks 26—30 weeks of gestation (group 1), 44 bones 31—36 weeks of gestation (group 2), and 37—40 weeks of gestation (full-term babies, group 3),The analysis of the data obtained on an individual bases revealed either increase or decreases in the selected characteristics of the eustachian tube in comparison with the respective average values as well as the well apparent predominance of a single change or a combination of alteration of several parameters in one case in 26—30 weeks and 31—36 weeks groups. No significant changes were found in group 1. It is concluded that the presence of a single change or a combination of two or three abnormal changes in the parameters of the bone structures of the eustachian tube can affect the development of the secretory process in the middle ear especially in the children born after 36 weeks of pregnancy.