Inclusion Criteria:  Breastfeeding women with healthy full-term, singleton infants older than 1 months weeks and younger than 6 months. Provide written informed consent  Exclusion Criteria:  Immunocompromised suppressed women (i.e. HIV, following treatment with immunosuppressants or chemotherapy). Currently being treated for cancer Current infection being treated with antibiotics. Women who carry out a complete deferred breastfeeding. Women with babies presenting any syndrome, cleft lip or facial malformations. Currently tandem breastfeeding. Women who have had a premature delivery