The Effect of Twin Birth on Neonatal and Infant Mortality Rates: A Systematic Review

Background and aims: Twin birth may account for higher mortality rates in infants and neonates. To investigate the potential relationship between twin birth and infant and neonatal mortality rates (NMRs), a systematic review was conducted. Methods: To gather the evidence for the relationship between twin birth and its potential effect on mortality during infancy and neonatal periods, a systematic review was conducted. The most important used databases were PubMed, Google Scholar, Web of Science, Scopus, ProQuest, Cochrane and Springer. Then, the databases were searched by appropriate keywords. After reviewing and evaluating the collected studies, trends in the different countries were compared. Results: A total of 13 790 related studies were found, of which 128 studies were selected in the first step. The studies which were not related to the subject, in addition to repetitive studies, were excluded from the search in the second step based on inclusion and exclusion criteria by reviewing the abstract and, in some cases, the full article. Finally, 7 studies entered the last step. Conclusion: This study showed that the mortality could be higher among twins than among non-twins, especially among boy