The case of a premature intra-uterine growth retardation (IUGR) infant, born from caesarean section to a mother with hemolysis, elevated liver enzymes, low platelets (HELLP) syndrome, and admitted to NICU for low birth weight is reported. The baby girl was fed with pasteurized maternal milk, and she had a normal growth. Before discharge, at the age of 23 days of life, she started to be breast-fed from the mother. Suddenly, the infant presented inconsolable crying, and then she appeared pale, hypothermic, and irritable. Eventually she showed apneic spells and hyperglycemia. A purple rash in the left submandibular area was noted. This rash rapidly progressed to painful hardening of the area. The neck ultrasonography revealed the presence of non-vascularized oval mass in the left submandibular area with an irregular sonostructure. The diagnosis of sepsis and submandibular phlegmon was confirmed by a positive blood culture for serotype III group B Streptococcus agalactiae. The polymerase chain reaction (PCR) assay for group B Streptococcus showed the presence of the same serotype in mother's milk. At 24 months of age the infant's neurodevelopment was normal.