Introduction.

Breastfeeding is a determinant for survival but natural process, its extension could harm the development of language? The objective is to determine the existence of scientific evidence on adverse or harmful effects of maternal or prolonged breastfeeding language development in infants of two or more years.

Method.

This is a secondary research literature in which the following databases are reviewed: Annual Reviews, Clinical Key, EBSCO, EBSCOHOST, Google Scholar, JAMA Network, Ovid and PubMed, to obtain 100 items. Once analyzed and applied the inclusion criteria, 19 papers were selected to answer the question PICO.

Results.

According to the design of the studies, nine of them present a level of evidence II-2, since they were cohort studies and case-control studies; then seven were constituted by literature reviews, of which four were systematic reviews; two are classified in level III of evidence because they were descriptive studies, a mixed descriptive and a qualitative one and, finally, one was constituted by a clinical trial that corresponds to the level of evidence I.

Conclusions.

Breastfeeding has a positive effect on language development: there is a causal relationship between duration of breastfeeding and receptive language and verbal and nonverbal intelligence.