Footnotes

• JZ and TL contributed equally to this article.

• Acknowledgements The authors thank all the families for participating.

• Contributors All authors were involved in drafting the article or revising it critically for important intellectual content, and all authors approved the final version to be published. CDB and QG were involved with conception and design, JZ and TL, acquisition of the data, and JZ, TL, SC and XFH, analysis and interpretation of the data. JZ and TL contributed equally to this article.

• Competing interests None.

• Patient consent Obtained.

• Ethics approval The local ethics committee at Renji Hospital, Shanghai Jiao Tong University School of medicine.

• Provenance and peer review Not commissioned; externally peer reviewed.