Received: 30 October 2017
Accepted: 9 January 2018
First Online: 22 January 2018
Ethics approval and consent to participate
: The study received ethical clearance from the Research Board at the Department of Obstetrics and Gynecology, Faculty of Medicine, University of Khartoum, Sudan.
: Not applicable.
: The authors declared that they have no competing interests.
: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.