Date	Event	Description
20 January 2021	New search has been performed	Search updated. All potentially eligible studies and studies already included in the review were assessed for trustworthiness. Three studies that were in the previous version of the review did not meet Pregnancy and Childbirth trustworthiness criteria and have not been included in this update. None of the studies identified in the search update met the trustworthiness criteria. No new studies added.
22 June 2020	New citation required but conclusions have not changed	Conclusions unchanged after removing data from studies that did not meet Pregnancy and Childbirth trustworthiness criteria.
3 May 2011	Amended	Corrected typo.