While still in the womb, the child recognizes the mother's voice and, even at birth, prefers to listen to speech rather than other sounds. Very early after birth, it is able to distinguish the mother's speech from the speech of others around it. From the moment of birth, the mother turns to the child and speaks to it, even though she knows that the child cannot yet understand language. The mother does this intuitively – with simplified language, shorter sentences, slower speech tempo and overemphasized prosody. The purpose of this work was to analyze the characteristics of mothers' speech during semi-structured interactions between mothers and children in their natural environment. Mothers and children aged 3, 6, 9, 12, 18 and 24 months were included in the study. During the interaction, mothers used the selected toys with instruction to present new toys to their children. This was done to create consistent conditions for all mothers and children, regardless of age. The interactions were recorded and subsequently evaluated. Both the linguistic features of the mother's speech and the features of the mother's communication were analyzed. The focus of the analysis was on developmental changes in the mother's language features as a function of the child's age. Results showed a slight increase in the mean length of utterance, the most common measure of syntactic complexity of speech, as the child's age increased. Thus, the mother's sensitivity to requests for simplified language decreases as the child ages, and the language becomes richer. Analysis of the collected data suggests that the linguistic features of maternal speech primarily reflect the mother's desire to attract the child's attention and to achieve communication and interaction with the child. This is manifested, as the results of this study show, in numerous repetitions of the same words, a high proportion of attention-seeking verbs, asking many questions, using the child's name to attract attention and using here-and-now themes. Also, during the first two years of child's life, the mother's communication with the children tends to serve the purpose of sharing interests and experiences with the children. During this time, mothers sometimes use gestures to support language. The data obtained from this study not only provide a more comprehensive understanding of an important environmental factor that enhances the orderly pattern of communication development and language acquisition, but also point to the need to pay special attention to the mother's language in stimulating the language and communication skills of children with developmental disabilities.