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who had a spontaneous vaginal delivery between 2004-2008. Cases were defined as women who had a max OT dose during labor 20 mU/min, while women in the control group had a max OT dose dur- ing labor of 20 mU/min. Exclusion criteria included no oxytocin administration during labor, operative vaginal or cesarean deliveries, multiple gestations, major fetal anomalies, nonvertex presentation, and prior cesarean delivery. Maternal factors evaluated included age, race, parity, body mass index (BMI), insurance status, diabetes and preeclampsia. Fetal factors assessed were gestational age and birth- weight 4000 gm. Induction of labor (IOL), Bishop score on admis- sion 6, regional anesthesia use and magnesium administration were also evaluated. Univariable analyses and multivariable logistic regres- sion was performed. Contraction parameters including frequency, baseline tone, and Montevideo units were compared between the groups. RESULTS: Max OT doses 20 mU/min were administered to 124 women (5%), while 2375 women received max OT doses 20 mU/ min. Factors associated with higher max OT dose after adjusting for relevant confounders included BMI, diabetes, birthweight 4000 gm and IOL. Contraction parameters did not differ between the groups. CONCLUSION: We identified clinical factors associated with a need for higher oxytocin doses to achieve a vaginal delivery. This data may be helpful to practitioners managing patients with these characteristics during labor. 314 Montevideo units: a poor predictor of second stage outcomes Heather Frey 1 , Methodius Tuuli 1 , Kimberly Roehl 1 , Anthony Odibo 1 , George Macones 1 , Alison Cahill 1 1 Washington University in St. Louis, Obstetrics and Gynecology, St. Louis, MO OBJECTIVE: Montevideo units (MVUs) are routinely used to evaluate adequacy of contractions, however studies suggest that the definition of normal contractions as 200 MVUs may not predict mode of de- livery (MOD). We sought to estimate the association between MVUs in the last 30 minutes (min) of labor and second stage outcomes. STUDY DESIGN: This retrospective cohort study included all women with intrauterine pressure catheters admitted at term to a single center from 2004-2008 who reached the second stage. Multiple gestations and major fetal anomalies were excluded. Contraction data during the last 30 min of labor was abstracted. Women with average contractions 200 MVUs were compared to women with contractions 200 MVUs. Primary outcomes were MOD, a composite neonatal outcome (arterial cord pH 7.1, 5-minute Apgar 7 or intensive care unit admission), and postpartum hemorrhage (PPH). We adjusted for parity, regional anesthesia, and oxytocin use with logistic regression. Receiver operating characteristic (ROC) curves were constructed to evaluate the predictive ability of MVUs. RESULTS: Contractions were “adequate” in 1,265 (53.7%) women, while 1,902 women had average contractions 200 MVUs. MVUs 200 was associated with a lower rate of operative delivery (cesarean, vacuum or forceps) (12.3% vs. 20.7%, aOR 0.52, p0.01) but no difference in the composite neonatal outcome (2.3% vs. 3.1%, p0.21) or PPH (2.4% vs. 2.5%, p0.79). Cord pH 7.1 was more common in women with 200 MVUs (2.0% vs. 0.9%, aOR 2.22, p0.03). ROC curves demonstrated that average MVUs were poorly predictive of MOD (AUC0.67), neonatal outcome (AUC0.58), and PPH (AUC0.59). ROC analyses were performed using alternate values to define contraction adequacy (MVUs 100, 150, 200, 250, 300), and regardless of the value used, MVUs were not predictive of the outcomes. CONCLUSION: While MVUs 30 min prior to delivery are associated with MOD, they are not predictive of second stage outcomes. Alternative measures of contractions should be studied and possibly incorporated into obstetric practice. 315 Differences in contraction patterns of women in spontaneous and non-spontaneous labor who deliver vaginally Heather Frey 1 , Methodius Tuuli 1 , Kimberly Roehl 1 , Anthony Odibo 1 , George Macones 1 , Alison Cahill 1 1 Washington University in St. Louis, Obstetrics and Gynecology, St. Louis, MO OBJECTIVE: To characterize and compare contraction patterns during the second stage of labor in women whose labor is augmented or induced (non-spontaneous) to those who spontaneously labor. STUDY DESIGN: A retrospective cohort study of all consecutive term births to women with intrauterine pressure catheters who had a spon- taneous vaginal delivery (SVD) admitted between 2004-2008 to a sin- gle hospital center. Multiple gestations, pregnancies complicated by major fetal anomalies, and women who delivered by cesarean or op- erative vaginal delivery were excluded. Uterine contraction patterns in the last thirty minutes prior to delivery were abstracted by formally trained obstetric research nurses. Contraction frequency, duration, Montevideo units (MVUs), and baseline uterine tone were compared in women with augmented or induced labor and women who spon- taneously labored. Logistic regression was used to adjust for maternal age, body mass index, preeclampsia, and parity. RESULTS: 1,647 women with induced or augmented labor were com- pared to 329 women with spontaneous labor. In both groups, the second stage of labor was characterized by an average of 200 MVUs in nearly half of women. The proportion of women with 200 MVUs was significantly higher among women in spontaneous labor (50.4% vs. 42.5%, aOR 1.40, p0.01). Spontaneous labor was also associated with a higher rate of baseline uterine tone 20 mmHg (72.0% vs. *n (%); †Adjusted for birthweight 4000gm, induction; ‡Adjusted for BMI, induction; ^Adjusted for birthweight 4000gm, BMI. Predicting operative delivery with varying MVUs www.AJOG.org Clinical Obstetrics, Diabetes, Labor, Medical-Surgical-Disease, Physiology/Endocrinology, Prematurity Poster Session II Supplement to JANUARY 2013 American Journal of Obstetrics & Gynecology S141
