Prevention of Recurrent Spontaneous Preterm Delivery Using Probiotics (Clostridium butyricum, Enterococcus faecium, and Bacillus subtilis; PPP Trial): Protocol for a Prospective, Single-Arm, Nonblinded, Multicenter Trial

Satoshi Yoneda   ^{1 *} , MD, PhD ;   Tohru Kobayashi   ^{2 *} , MD, PhD ;   Kayoko Kikuchi   ^{3 *} , PhD ;   Shintaro Iwamoto   ^{4 *} , MD, PhD ;   Tsuyoshi Teramoto   ^{5 *} , PhD ;   Daisuke Chujo   ^{5 *} , MD, PhD ;   Katsufumi Otsuki   ^{6 *} , MD, PhD ;   Akihito Nakai   ^{7 *} , MD, PhD ;   Shigeru Saito   ^{8 *} , MD, PhD

¹ Department of Obstetrics and Gynecology, University of Toyama, Toyama, Japan

² Department of Data Science, Clinical Research Center, National Center for Child Health and Development, Tokyo, Japan

³ Center for Translational Research, Translational Research Headquarters, Fujita Health University, Aichi, Japan

⁴ Biostatistics Unit, Department of Data Science, Clinical Research Center, National Center for Child Health and Development, Tokyo, Japan

⁵ Center for Clinical Research, Toyama University Hospital, Toyama, Japan

⁶ Department of Obstetrics and Gynecology, Showa University Koto Toyosu Hospital, Tokyo, Japan

⁷ Department of Obstetrics and Gynecology, Nippon Medical School Tama-Nagayama Hospital, Tokyo, Japan

⁸ University of Toyama, Toyama, Japan

*all authors contributed equally