87 ARE THERE DIFFERENCES IN MECHANICAL FETAL RESPONSE BETWEEN ROUTINEAND SHOULDER DYSTOCIA DELIVERIES? ROBERT ALLEN1, STEPHANIE CHA1,LINDSAY KRANKER1, TARA JOHNSON1, EDITH GUREWITSCH2, 1Johns HopkinsUniversity, Biomedical Engineering, Baltimore, Maryland, 2Johns HopkinsUniversity, Gynecology and Obstetrics, Baltimore, Maryland

OBJECTIVE: Previous simulations of shoulder dystocia (SD) explored theeffect of SD itself on the mechanical response of the fetus. Our objective was toperform an experimental study to explore the variations in fetal response dueto routine, unilateral SD (USD) and bilateral SD (BSD) deliveries.

STUDY DESIGN: Using a biofidelic maternal model, an instrumented fetalmodel and a data-acquisition system, we performed 30 experiments. Forroutine deliveries, we engaged the fetal head and allowed it to progressthrough cardinal movements using typical uterine contraction forces of 20-35lbs, stopping the delivery when the head restituted to LOA presentation. ForUSD deliveries, we obstructed the anterior shoulder on the symphysis pubis;for BSD, the posterior shoulder was also impacted on the sacral promontory.Fetal shoulder widths were varied from 11.5, 12.9 and 12.1 cm, respectively forroutine, USD and BSD deliveries. For each delivery we continuously measuredhead rotation (HR), brachial plexus (BP) stretch and neck extension (NE),selecting peak values for analysis. Maximum BP stretch, NE and HR werecompared among groups using ANOVA, with P!0.05 considered significant.

RESULTS: The table lists mean peak BP stretch, HR and NE amongroutine, USD and BSD deliveries. There are no differences among the threetypes of delivery for anterior BP stretch, HR and NE.

CONCLUSION: Quantifiable mechanical response occurs in routine and SDdeliveries. Posterior BP stretch is significantly longer for routine deliveries thaneither USD or BSD deliveries.

88 PREDICTING CEPHALOPELVIC DISPROPORTION (CPD) IN LABOR UTILIZINGUTERINE TOCODYNAMOMETRY JANYNE ALTHAUS (F)1, RITA DRIGGERS1,SCOTT PETERSEN1, ALICE COOTAUCO1, KARIN BLAKEMORE1, 1Johns HopkinsUniversity, Gynecology and Obstetrics, Baltimore, Maryland

OBJECTIVE: To determine if intrapartum contractions of a particular shape(rapid rise with slower return to baseline) are predictive of CPD.

STUDY DESIGN: Prospective cohorts of 100 women each who underwentspontaneous vaginal delivery (SVD) vs Cesarean section (C/S) for CPD orarrest of labor were consecutively identified. Inclusion criteria included term,singleton pregnancies, nulliparity and absence of fetal anomalies. One hour ofinterpretable EFM was obtained in active labor. Fall to rise (F:R) ratio wascalculated by measuring the time for a contraction to return to baseline fromits peak (‘‘fall’’) and the time for a contraction to rise to its peak (‘‘rise’’); F:Rswere then averaged over the number of contractions. Data were analyzed usingStudent’s t-test, Chi-square, Fisher’s exact tests and ANOVA whereappropriate.

RESULTS: The average F:R ratio was 1.55 for SVD vs 1.77 for C/S(p=0.0003). ANOVA revealed this difference persists when controlling forpotentially confounding factors. (Table) Increasing F:Rs were associated withhigher birthweights (p=0.06). The positive predictive value (PPV) for CPDincreased with increasing F:R in the study subjects: F:R = 1.2, PPV = 50%;F:R = 1.4, PPV=54%; F:R = 1.6 PPV=63%; F:R = 1.8 PPV = 70%;F:R = 2.0, PPV=73%.

CONCLUSION: Our study demonstrates a uterine contraction configurationthat is more common in those labors destined for C/S due to CPD. Thissuggests the activation of a potential feedback mechanism by the uterus as itadapts to a relative or absolute CPD.

Maternal demographics

SVD C/S p-value

Age (yrs) 23.5 25.6 0.032Gestational age (wks) 39.3 40.0 !0.001Race (%white) 23 30 0.226Diabetes (%) 3 2 1.00Magnesium in labor (%) 4 5 1.00Epidural (%) 89 96 0.105Pitocin (%) 77 88 0.041Induction (%) 45 65 0.003IUPC (%) 38 59 0.005ROM (%) 79 87 0.132Chorioamnionitis 8 23 0.003Birthweight (g) 3218 3562 !0.0001F:R 1.55 1.77 0.00003

89 COMPLICATION RATES IN MULTIPARAS UNDERGOING LABOR INDUCTIONCOMPARED TO MULTIPARAS EXPERIENCING SPONTANEOUS LABORLEAH BATTISTA (F)1, DAVID LAGREW2, ANNA MCKEOWN1, DEBORAH WING1,1University of California, Irvine, OB/Gyn Maternal Fetal Medicine, Orange,California, 2Saddleback Memorial Medical Center, Maternal FetalMedicine, Laguna Hills, California

OBJECTIVE: The increased complication rates including cesarean sectionrates are clearly demonstrated for nulliparas undergoing labor inductioncompared to those experiencing spontaneous labor. The goal of this investi-gation is to compare complication rates in multiparas undergoing laborinduction compared to multiparas experiencing spontaneous labor.

STUDY DESIGN: A retrospective cohort using a quality assurance databaseof prospectively collected data. All multiparas with term, singleton pregnanciesin vertex presentation without contraindications to labor at four hospitalsfrom 1/2003-12/2004 undergoing labor induction and spontaneous labor wereidentified. The groups were compared for various complications of labor anddelivery in the mothers and infants. Statistical analysis was done using c2

analysis with rate ratios to compare differences.RESULTS: There were a total of 2,416 women undergoing labor induction

and 8,016 women experiencing spontaneous labor in this time period. Wheninduced patients were compared to spontaneous labor patients, cesareansection 7.5% vs.5.4%, RR 1.4 (1.19-1.66), estimated blood loss O500cc 9.4%vs. 6.5%, RR 1.62 (1.26-1.69) and O12 hours labor duration 26.3% vs. 9.8%,RR 2.69 (2.45-2.95) were found to be significantly more common. There wereno differences in vaginal/perineal lacerations, estimated blood loss greater than1000cc, admissions to the NICU, APGAR scores, or operative vaginal deliverybetween the two groups.

CONCLUSION: Labor induction in multiparas increased cesarean sectionrates, blood loss and chances for prolonged labor. These risks should be sharedwith paients undergoing labor induction.

90 FETAL SAFETY OF UTERO-VAGINAL SODIUM NITROPRUSSIDE APPLICATION INSHEEP IMMACOLATA BLASI1, BRYAN RICHARDSON2, BRAD MATUSHEWSKI2,SHANNON HEMSTREET2, FABIO FACCHINETTI1, 1University of Modena & ReggioEmilia, Mother-infant Dept., Modena, Italy, 2University of Western Ontario,Physiology & Pharmacology, London, Ontario, Canada

OBJECTIVE: The aim of this study is to evaluate the safety of SodiumNitroprusside (SNP) administration in the cervix of near term sheep.

STUDY DESIGN: Chronically catheterized pregnant sheep at w 0.9 gestationwere divided into three study groups: Cerv group (n=8) received 0.1 mg/kgestimated maternal body weight of SNP gel (2%) in the extra-amniotic spacenear the internal os of the cervix; Plac group (n=6) received a placebo gel in asimilar volume at the same site; Vag group (n=5) received SNP gel in a similarvolume in the vaginal posterior fornix. SNP or placebo gel were administeredat 9 am on day one of study with fetal blood gas/pH and blood pressure (FBP)monitored immediately before (time 0) and for 24 hours thereafter.

RESULTS: No significant changes were induced by SNP or by Plac except aslight transient increase of fetal lactate just after SNP administration in thecervical than in vaginal group. We also recorded a decrease of fetal BaseExcess. Nonetheless, they are minimal and unlikely to be of any clinicalsignificance. FBP does increase in the SNP groups indicating a effect of thedrug which is not surprising but generally well tolerated to the extent fetalblood gases and pH remain little changed. However, this may not be the casein the IUGR fetus with a compromise in placental function and oxygenationwho may not tolerate so readily these cardiovascular effects if umbilical bloodflow is also effected.

CONCLUSION: These data demonstrate few, if any, effects of intrauterineand vaginal SNP administration on both cellular oxygenation and cardiovas-cular indexes. Thus, such treatment could be considered a safe procedure forfetus.

(data reported as mean D/� SEM, * [ p! 0.05 vs baseline)

Lactate FBP

Time Cerv Vag Plac Cerv Vag Plac

0 .8G.1 1G0.1 .7G.2 35G5.6 40G5 38G6.50.45 .9G.1* 1.2G0.2 1G.6 39G2.3* 45G3* 39G5.62.5 .8G.1 1.1G0.1 .9G.3 38G6.9 43G3 32G9.36 .8G.1 1.1G0.1 .8G.2 38G4.5 45G3* 35G7.811 .8G.1 1.4G0.2* 1.1G.7 43G9.3 45G3 36G8.624 1G.2 1.2G0.2 1G.3 46G11.2 48G5 41G11

S38 SMFM Abstracts