In the context of the increasing fertility treatments and consolidating of medical resources, the number of multiple pregnancies delivered at perinatal centers is recently increasing. However, few reports focused on the rate of multiple births delivered at perinatal centers. In this study conducted at a tertiary perinatal center, Hyogo Prefectural Kobe Children’s Hospital Perinatal Center, 9,559 newborns who delivered between 1995 and 2020, and their mothers were investigated. During the study period, the rate of mothers with more than 35 years of life increased from 10.4 to 34.2%. Concurrently, the rate of pregnancy with fertility treatments, including timing of intercourse, artificial insemination with husband, ovulation induction, and assisted reproductive technologies, also increased from 2.3 to 26.3%. As a result, the rates of multiple pregnancies and births were increased from 7.7 and 15.3% to 22.3 and 37.2%, respectively. At our tertiary perinatal center, multiple pregnancies and births are significantly increasing during recent decades.