Acknowledgments
The authors are grateful to the following staff members for their great support in data collection: Yuri Asano, Mio Sano, Natsumi Tsuchiya, Miyuki Takeuchi, Sana Ohno, Nozomi Kobayashi, Asami Nagatani, Hitomi Yuasa, and Saori Ikeda, who are the members of the Recurrence Prevention Committee, Japan Obstetric Compensation System for Cerebral Palsy, Public Interest Incorporated Foundation Japan Council for Quality Health Care.
Conflict of interest: We declare no competing interests.
Author contributions statement: JH, NM, TI, and TI conceived the study. JH wrote the initial protocol, analyzed the data, and wrote the first draft of the manuscript. All authors collected data and analyzed cases of CP. JH, MN, TI, and EJ coordinated the study and JH, MN, TI, and EJ produced the database. Statistical analyses were performed by ST and NT. All authors contributed to writing the manuscript. TI, SS, KI, ST, AN, KF, TM, ST, HS, MI and TI are the guarantors for the study. All authors had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis. The lead author affirms that this manuscript is an honest, accurate, and transparent account of the study being reported; that no important aspects of the study have been omitted; and that any discrepancies from the study as planned have been explained.
Funding: None.
Details of ethics approval: Alll procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki declaration and its later amendments or comparable ethical standards. The study protocol was approved by the Institutional Review Boards (IRBs) of the JOCSC (No.26-01, Aug. 5th 2014).
Data sharing: No additional data is available.