Labor dystocia and its association with interpregnancy interval Bao-Ping Zhu, MD, MS, a, * Violanda Grigorescu, MD, MSPH, b Thu Le, PhD, b Mei Lin, MD, MSc, a Glenn Copeland, MBA, b Maurice Barone, PhD, b George Turabelidze, MD, PhD a Office of Epidemiology, Missouri Department of Health and Senior Services, a Jefferson City, MO; Bureau of Epidemiology, Michigan Department of Community Health, Lansing, MI b Received for publication August 23, 2005; revised November 9, 2005; accepted December 5, 2005 KEY WORDS Interpregnancy interval Dystocia Objective: The purpose of this study was to evaluate the prevalence of labor dystocia and its association with interpregnancy interval. Study design: We linked the birth data for Michigan infants who were born from 1994 to 2002 with the hospital discharge data. The International Classification of Diseases (9th revision, clin- ical modifications, ICD-9-CM) codes that indicate labor dystocia were identified by a physician panel and classified as functional and mechanical dystocia. We estimated the prevalence of labor dystocia and used stratified and logistic regression analyses to evaluate labor dystocia in relation to interpregnancy interval, controlling for other reproductive risk factors. Results: Overall, 20.8% of the births involved labor dystocia (11.1% functional; 12.5% mechan- ical). Both functional and mechanical dystocia were more prevalent in first births than in subse- quent births; mechanical dystocia was more prevalent in multiple births than in singleton births. In singleton births to multiparous mothers, labor dystocia was associated with the interpregnancy interval in a dose-response fashion. Compared with an interpregnancy interval of !2 years, the adjusted odds ratios that was associated with interpregnancy intervals of 2 to 3, 4 to 5, 6 to 7, 8 to 9, and 10C years were 1.06 (95% CI, 1.04-1.08), 1.15 (95% CI, 1.12-1.17), 1.25 (95% CI, 1.21- 1.29), 1.31 (95% CI, 1.26-1.37), and 1.50 (95% CI, 1.45-1.56), respectively, when we controlled for other reproductive risk factors. Functional dystocia was associated more strongly with inter- pregnancy interval than mechanical dystocia. Conclusion: Labor dystocia is common. In singleton births to multiparous mothers, labor dysto- cia increased with interpregnancy interval. Ó 2006 Mosby, Inc. All rights reserved. Labor dystocia, also known as ‘‘dysfunctional labor’’ or ‘‘difficult childbirth,’’ is common among women during labor and delivery and can have serious con- sequences (including maternal deaths), especially in * Reprint requests: Bao-Ping Zhu, MD, MS, Office of Epidemiol- ogy, Missouri Department of Health and Senior Services, 330 Wild- wood Dr, PO Box 570, Jefferson City, MO 65102. E-mail: BaoPing.Zhu@dhss.mo.gov 0002-9378/$ - see front matter Ó 2006 Mosby, Inc. All rights reserved. doi:10.1016/j.ajog.2005.12.016 American Journal of Obstetrics and Gynecology (2006) 195, 121–8 www.ajog.org