Funding for this research was provided by:
Health Technology Assessment Programme (12/01/50)
World Health Organization (not available)
Received: 23 April 2018
Accepted: 22 August 2019
First Online: 2 September 2019
Ethics approval and consent to participate
: The work uses pseudonymised data from clinical trials with ethical approvals from the relevant local committees. The National Institute for Health Research approved the development of the i-WIP IPD repository under the research grant contract (No. 12/01/50). Also the outline of this work has been assessed and approved by the i-WIP Data Access Committee.
: The submitted work is a secondary analysis using IPD data from randomised trials and does not require publication consent from the participants of the original trials. All investigators gave consent to use IPD from their trials for this analysis and the publication of its results.
: FGS is a member of the editorial board (Associate Editor) of BMC Pregnancy and Childbirth. The remaining authors declare that they have no competing interests.