Predictors of cesarean section following elective post-dates induction of labor in nullipara with uncomplicated singleton vertex pregnancies Fawaz E. Edris, MD, FRCSC, Peter von Dadelszen, DPhil, FRCSC, Laurie M. Ainsworth, MSc, Robert M. Liston, FRCOG, FRCSC. D uring an uncomplicated pregnancy, the risk of interrupting the pregnancy outweighs the risks of allowing the pregnancy to continue naturally until the onset of spontaneous labor. However, induction of labor has therapeutic merit when the beneits of an From the Department of Obstetrics and Gynecology, Children’s and Women’s Health Centre of British Columbia (Edris, von Dadelszen, Liston), and Centre for Healthcare Innovation and Improvement (von Dadelszen), and Clinical Research Support Unit, British Columbia, Research Institute for Children’s and Women’s Health, (Ainsworth), University of British Columbia, Vancouver, Canada. Received 21st November 2005. Accepted for publication in inal form 24th April 2006. Address correspondence and reprint request to: Dr. Fawaz Edris, University of Western Ontario, 202-665 Windermere Rd, London, Ontario, Canada. Tel. +1 (519) 9133033. Fax. +1 (519) 6633162. E-mail: fawazedris@yahoo.ca 1167 expedited delivery outweigh the risks of continuing the pregnancy. In response to the post-term trial, 1 post-term pregnancy is the most common indication for induction in our institution. In nullipara, overall induction is associated with twice the risk of cesarean Objectives: Although “post-dates” is among the most common indications for induction of labor, no studies have identiied the predictors of cesarean section (C/S) in that population. The high cesarean rate in our institution for this group of women triggered us to assess different induction practices to elicit potential causes. Methods: We conducted a hospital-based retrospective cohort analysis using chart reviews of all nullipara women with induced labor at the Children’s and Women’s Health Centre of British Columbia, Vancouver, Canada, during the 2-year period, April 1998 to March 2000. The C/S rate was compared among 3 groups of women who were divided according to their induction method. Results: Three hundred and thirty-nine women meeting the inclusion criteria were induced. Of the 25 women who received oxytocin “ideally” and the 111 women who did not, 7 (28%) and 53 (48%) were delivered by C/S, (χ 2 =3.228 ABSTRACT p=0.07; relative risks 0.59 [95% conidence interval 0.30, 1.13]). A signiicantly lower C/S rate (χ 2 =21.9, p<0.0005) was found among women induced with prostaglandin (PG) alone (19.4%) compared with those induced with PG and oxytocin, whether oxytocin was given “ideally” (38.3%) or “not ideally” (45.4%). Of women who received oxytocin, there was no difference in chorioamnionitis (χ 2 =0.485, p=0.49) between those who had an early membrane rupture (with or pre-oxytocin, 22.4%) and those who had membrane rupture following a period of oxytocin infusion (18.5%). Conclusion: The need for oxytocin or >2 doses of PG is associated with increased risk of C/S. Whether oxytocin was given according to protocol (ideally) or not, made no difference to the C/S risk in this population. Saudi Med J 2006; Vol. 27 (8): 1167-1172 10Predictors20051330.indd 1167 7/18/06 12:54:45 PM