Poster session II Diabetes, labor, medical-surgical-disease, obstetric quality & safety, prematurity, ultrasound-imaging: Abstracts 237 – 386| Volume 206, ISSUE 1, SUPPLEMENT , S151, January 01, 2012

318: The association between induction of labor and primary cesarean delivery in the Northeastern U.S. between 1996 and 2004


      The annual incidence rates of labor induction and cesarean delivery have increased dramatically over the past decade. We aim to examine the association between induction of labor and cesarean delivery among low risk nulliparous women in the northeastern U.S. over time.

      Study Design

      This was a retrospective cohort study of non-anomalous, singleton, term, vertex live births by nulliparous women in the northeastern U.S. states between 1996 and 2004 using the U.S. Natality birth data. We excluded medical and obstetric conditions, yielding a low-risk population. The association between labor induction and cesarean delivery was examined by time trend in 2-year intervals using chi-square test and multivariable logistic regression. Population-based expected and observed numbers of cesareans over time were estimated using baseline cesarean risk and adjusted odds ratio based on induction of labor.


      There were 1,300,393 live births meeting study criteria; of these, 21.4% had cesarean delivery. Compared to women without induction of labor, those induced had about 1.5 times the adjusted odds of cesarean: 1.58 for 1996 and 1998, 1.55 for 2000, 1.54 for 2002, and 1.55 for 2004. Of note, these odds ratios remained stable over the study period. However, the difference between observed and expected numbers of cesarean sections increased over time (Figure).


      While nulliparous women who had induction of labor had higher odds of cesarean, this effect estimates were stable over time. However, the actual number of cesarean deliveries increasingly deviated from the expected amounts, suggesting that increase in labor induction only provides partial explanation for the current cesarean epidemic.