Background. Ankyloglossia, commonly known as tongue-tie, reduces tongue mobility through restriction of the lingual frenulum. A recent professional consensus notes that tongue-tie is one possible reason for breastfeeding challenges. Prevalence reporting of tongue-tie has been variable, and an understanding of which infants benefit most from treatment is unknown.Screening and treatment guidelines have not been developed, mainly due to low-level evidence in published research. Despite this, there has been a substantial increase in tongue-tie treatment via frenotomy in the last 15 years. Purpose. The purpose of this program of research was to improve our understanding of tongue- tie and its impact on infant feeding. Eight specific aims were developed to achieve this purpose: 1) identify the prevalence rate of anyloglossia in infants age birth through 12 months; 2) review and evaluate the diagnostic criteria used to diagnose ankyloglossia; 3) identify and summarize original research addressing the impact of ankyloglossia on infant feeding, comparing symptoms of problematic feeding before and after frenotomy; 4) review the quality of the feeding-related outcome measures and psychometric properties of the assessment tools used; 5) describe changes in problematic feeding symptoms, as measured by the NeoEAT, pre- and post-frenotomy; 6) explore the contribution of infant age to the magnitude of change in problematic feeding pre- and post-frenotomy; 7) describe changes in maternal symptoms pre- and post-frenotomy; and 8) evaluate the relationships between maternal symptoms and symptoms of problematic feedingpre- and post-frenotomy. Methods. First, we performed a systematic review and meta-analysis of the literature on tongue- tie to determine the prevalence of the anomaly in the infant population and critiqued the methods used to achieve tongue-tie diagnosis. Second, we identified and summarized original research addressing the impact of tongue-tie on infant feeding, comparing symptoms of problematic feeding before and after frenotomy. In this same study, we evaluated the psychometric properties of the assessment tools used in the published research. Next, we assessed maternal and infant symptoms of problematic feeding pre- and post-frenotomy. In this same study, we utilized a comprehensive evaluation of infant feeding symptoms using a validated measure. Results. Cumulatively, this dissertation research has identified symptoms in both mothers and their infants in the setting of tongue-tie. Each of the eight specific aims proposed for this dissertation were addressed. Specifically, through the meta-analysis and systematic review, we determined 1) prevalence of tongue-tie is higher than previously thought, affecting 8% of the infant population, 2) current screening tools for tongue-tie require psychometric evaluation, 3) LATCH scores and maternal self-efficacy improve following frenotomy but little is known about the effect of frenotomy on infant feeding, and 4) infant feeding has not been evaluated comprehensively or with a validated measure for babies with tongue-tie. The research study conducted in Chapter IV found that 5) infants with severe tongue-tie experienced significant improvements in problematic feeding symptoms following tongue-tie correction as measured by the NeoEAT, 6) regardless of infant age, improvements in symptoms of problematic feeding were seen post-frenotomy in babies with severe tongue-tie, 7) maternal symptoms previously thought to occur in the setting of tongue-tie improved following frenotomy (e.g., painful or difficult latch), and 8) symptoms that have not been assessed in earlier research also improved after tongue-tie correction (e.g., chewing on nipple, incomplete breast drainage, and over supply of breastmilk). Conclusions. The program of research in this dissertation has made meaningful contributions to the literature on tongue-tie. Through the production of the first meta-analysis of prevalence data, a thorough evaluation of the available research, and the determination of maternal and infant symptoms associated with tongue-tie, we have crafted recommendations for future research and recommendations for improvements in the clinical management of infants with this oral anomaly.