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www.AJOG.org Clinical Obstetrics, Diabetes, Labor, Medical-Surgical-Disease, Physiology/Endocrinology, Prematurity Poster Session II

who had a spontaneous vaginal delivery between 2004-2008. Caseswere defined as women who had a max OT dose during labor �20mU/min, while women in the control group had a max OT dose dur-ing labor of �20 mU/min. Exclusion criteria included no oxytocinadministration 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 andpreeclampsia. 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 werealso evaluated. Univariable analyses and multivariable logistic regres-sion was performed. Contraction parameters including frequency,baseline tone, and Montevideo units were compared between thegroups.RESULTS: Max OT doses �20 mU/min were administered to 124

omen (5%), while 2375 women received max OT doses �20 mU/in. Factors associated with higher max OT dose after adjusting for

elevant confounders included BMI, diabetes, birthweight �4000 gmnd IOL. Contraction parameters did not differ between the groups.

CONCLUSION: We identified clinical factors associated with a need forhigher oxytocin doses to achieve a vaginal delivery. This data may behelpful to practitioners managing patients with these characteristicsduring labor.

314 Montevideo units: a poor predictorf second stage outcomes

Heather Frey1, Methodius Tuuli1, Kimberly Roehl1,nthony Odibo1, George Macones1, Alison Cahill1

1Washington University in St. Louis, Obstetrics and Gynecology,t. Louis, MO

OBJECTIVE: Montevideo units (MVUs) are routinely used to evaluatedequacy of contractions, however studies suggest that the definitionf normal contractions as �200 MVUs may not predict mode of de-

ivery (MOD). We sought to estimate the association between MVUsn the last 30 minutes (min) of labor and second stage outcomes.

STUDY DESIGN: This retrospective cohort study included all womenwith intrauterine pressure catheters admitted at term to a single centerfrom 2004-2008 who reached the second stage. Multiple gestationsand major fetal anomalies were excluded. Contraction data during thelast 30 min of labor was abstracted. Women with average contractions�200 MVUs were compared to women with contractions �200MVUs. Primary outcomes were MOD, a composite neonatal outcome(arterial cord pH �7.1, 5-minute Apgar �7 or intensive care unitadmission), and postpartum hemorrhage (PPH). We adjusted forparity, regional anesthesia, and oxytocin use with logistic regression.Receiver operating characteristic (ROC) curves were constructed toevaluate the predictive ability of MVUs.RESULTS: Contractions were “adequate” in 1,265 (53.7%) women,

hile 1,902 women had average contractions �200 MVUs. MVUs

*n (%); †Adjusted for birthweight �4000gm, induction; ‡Adjusted for BMI, induction; ^Adjusted forbirthweight �4000gm, BMI.

200 was associated with a lower rate of operative delivery (cesarean,

Supplem

vacuum or forceps) (12.3% vs. 20.7%, aOR 0.52, p�0.01) but nodifference in the composite neonatal outcome (2.3% vs. 3.1%,p�0.21) or PPH (2.4% vs. 2.5%, p�0.79). Cord pH �7.1 was morecommon in women with �200 MVUs (2.0% vs. 0.9%, aOR 2.22,p�0.03). ROC curves demonstrated that average MVUs were poorlypredictive of MOD (AUC�0.67), neonatal outcome (AUC�0.58),and PPH (AUC�0.59). ROC analyses were performed using alternatevalues to define contraction adequacy (MVUs �100, 150, 200, 250,300), and regardless of the value used, MVUs were not predictive ofthe outcomes.CONCLUSION: While MVUs 30 min prior to delivery are associated withMOD, they are not predictive of second stage outcomes. Alternativemeasures of contractions should be studied and possibly incorporatedinto obstetric practice.

315 Differences in contraction patterns of women inpontaneous and non-spontaneous labor whoeliver vaginally

Heather Frey1, Methodius Tuuli1, Kimberly Roehl1, Anthonydibo1, George Macones1, Alison Cahill1

1Washington University in St. Louis, Obstetrics and Gynecology,t. Louis, MO

OBJECTIVE: To characterize and compare contraction patterns duringhe second stage of labor in women whose labor is augmented ornduced (non-spontaneous) to those who spontaneously labor.

STUDY DESIGN: A retrospective cohort study of all consecutive termbirths 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 bymajor fetal anomalies, and women who delivered by cesarean or op-erative vaginal delivery were excluded. Uterine contraction patterns inthe last thirty minutes prior to delivery were abstracted by formallytrained obstetric research nurses. Contraction frequency, duration,Montevideo units (MVUs), and baseline uterine tone were comparedin women with augmented or induced labor and women who spon-taneously labored. Logistic regression was used to adjust for maternalage, body mass index, preeclampsia, and parity.RESULTS: 1,647 women with induced or augmented labor were com-

ared to 329 women with spontaneous labor. In both groups, theecond stage of labor was characterized by an average of �200 MVUsn 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, p�0.01). Spontaneous labor was also associated

Predicting operative delivery with varying MVUs

with a higher rate of baseline uterine tone �20 mmHg (72.0% vs.

ent to JANUARY 2013 American Journal of Obstetrics & Gynecology S141