We would like to thank the Managing Editor of the Pregancy and Childbrith Group, Sonja Henderson, for her encouragement and advice that led to the registration of the topic for this protocol. We also thank Frances Kellie, the current Managing Editor of the Pregnancy and Chilbirth Group, for her numerous encouragements and words of advice.

Special thanks to Tamara Kredo, Elizabeth Pienaar, Babalwa Zani, Joy Oliver, Solange Durao, Charles Okwundu and Kholiswa Dube of the South African Cochrane Centre for encouraging us in the writing of protocols for systematic reviews. We are grateful to the Nigerian branch of the South African Cochrane Centre (SACC) and GJ Hofmeyr of the Effective Care Research unit, East London, for training us in the conduct of protocol writing. We would also like to thank Denise Atherton, the Administrative Assistant of the Cochrane Pregnancy and Childbirth Group for all her support towards the completion of this protocol.

George Eleje (GE) was awarded a fellowship by the South African Cochrane Centre through a grant received from the Effective Health Care Research Consortium (www.evidence4health.org), which is funded by UKaid from the UK Government for International Development. GE acknowledges the Faculty of Medicine, College of Health Sciences, Nnamdi Azikiwe University, Nnewi Campus, for providing the enabling environment for staff development that allowed him to attend the Fellowship Course in South Africa.

As part of the prepublication editorial process, this protocol has been commented on by three peers (an editor and two referees who are external to the editorial team), a member of Cochrane Pregnancy and Childbirth's international panel of consumers and the Group's Statistical Adviser.

This project was supported by the National Institute for Health Research, via Cochrane Infrastructure funding to Cochrane Pregnancy and Childbirth. The views and opinions expressed therein are those of the authors and do not necessarily reflect those of the Systematic Reviews Programme, NIHR, NHS or the Department of Health.