Number of days from insertion of intrauterine device or intrauterine system to first major event in patients receiving frequent or infrequent systematic checks. Number of days from insertion of intrauterine device or intrauterine system to first major event in patients receiving frequent or infrequent systematic checks. Isabel B Draper et al. J Fam Plann Reprod Health Care 2012;38:15-18 Copyright © by the BMJ Publishing Group Ltd & the Faculty of Sexual & Reproductive Healthcare of the Royal College of Obstetricians & Gynaecologists. All rights reserved.