ABSTRACT
BACKGROUND: Upper lip tie (ULT) articles have been recorded in Medline since 1998, while "labial frenum" articles have been recorded since 1946. OBJECTIVE: to study the existing medical literature on ULT (or labial frenum or fraenum) as they relate to breastfeeding. MATERIALS AND METHODS: Medline search engine was used to determine and subsequently retrieve all articles published on ULT from 1946 to 2018. Key-words of upper lip tie OR labial frenum were used for the search. We also used Google Scholar and Embase to widen our search, and used the PRISMA criteria for systematic reviews (SRs). Articles were classified as case reports (or series), reviews, editorials (or opinions), cohort studies, clinical trials (nonrandomized), randomized controlled trials (RCT), and SRs according to Medline's own classification. We systematically summarized all articles published to date. RESULTS AND CONCLUSION: No RCT were found, and the evidence for routine ULT release in infants with breastfeeding difficulties is poor. The classification system proposed by Kotlow has not been found reliable both in terms of inter and intraobserver agreement and in terms of predicting the severity of the breastfeeding difficulties.