Acknowledgements
We thank Silvia Andreozzi and Mauro Bucciarelli for their valuable technical support and assistance to the operation of the web-based data collection system.
We thank Clarissa Bostford for language editing.
Our heartfelt thanks go to all the clinicians working in the national network of maternity units (Appendix 1) for the assistance offered to women and for collecting the data, we thank all women who agreed to participate in the study.
Disclosure of interest
All authors have completed the ICMJE uniform disclosure form and declare no support from any organisation for the submitted work; no financial relationships with any organisations that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.