544 FORCEPS VS. VACUUM: WHICH IS ASSOCIATED WITH THE GREATEST MORBIDITY?AARON B. CAUGHEY1, PER SANDBERG2, MARYA ZLATNIK1, JULIAN T. PARER1, MARI-PAULE THIET1, RUSSELL K. LAROS JR1, 1University of California, San Francisco,Obstetrics, Gynecology and Reproductive Sciences, San Francisco, California,2California Pacific Medical Center, Obstetrics and Gynecology, San Francisco,California

OBJECTIVE: To compare perinatal outcomes between forceps and vacuumassisted deliveries. Our hypothesis was that the force vectors achieved in forcepsdelivery will lead to fewer shoulder dystocia, but greater perineal lacerations.

STUDY DESIGN: This is a retrospective cohort study of 4120 term, cephalic,singleton, operative vaginal deliveries at a single institution. Outcomes examinedincluded rates of shoulder dystocia, perineal and cervical lacerations, andneonatal trauma. Potential confounders including maternal age, birthweight,ethnicity, parity, gestational age, station at delivery, episiotomy, attendingphysician, anesthesia, and lengths of 1st and 2nd stages of labor were controlledfor using multivariate logistic regression.

RESULTS: In the study population, there were 2045 (49.6%) forceps and 2075(50.4%) vacuum assisted deliveries. Of note, the rate of shoulder dystocia washigher among women undergoing vacuum assisted delivery (3.5% vs. 1.5%, P!.001). Other differences are reported in the table below. These differences inperinatal complication rate persisted when controlling for the confounders listedabove with adjusted odds ratio for shoulder dystocia being 3.05 (95% CI 1.85–5.04), and 3rd or 4th degree lacerations being 0.65 (95% CI 0.55–0.75) whencomparing vacuum to forceps.

CONCLUSION: Vacuum assisted vaginal birth is more often associated withshoulder dystocia and cephalohematoma. Forceps delivery is more oftenassociated with 3rd and 4th degree perineal lacerations as well as cervicallacerations. These differences in complications rates should be considered amongother factors when determining the optimal mode of delivery.

Outcomes Forceps Vacuum P value

Shoulder dystocia 1.5% 3.5% ! .0013rd/4th degree 36.9% 26.8% ! .001Cervical lac 3.0% 1.5% ! .001Birth trauma* 1.7% 2.1% .389Cephalo- hematoma 4.5% 14.8% ! .001

* Birth trauma includes: skull fx, clavicle fx, erbs palsy, intracranial hemorrhage,and facial nerve palsy.

545 OBSTETRIC OUTCOME OF SECOND DELIVERY FOLLOWING FIRST DELIVERY OFA MACROSOMIC INFANT (O4.5KG) RHONA MAHONY1, MICHAEL E. FOLEY1,LESLIE DALY2, COLM O’HERLIHY1, 1University college Dublin, Obstetrics andGynaecology, Dublin, Ireland, 2University College Dublin, Public HealthMedicine & Epidemiology, Dublin, Ireland, Ireland

OBJECTIVE: Fetal macrosomia is associated with dystocia and increasedmaternal and perinatal morbidity and predisposes to macrosomia in subsequentpregnancies. Our aim was to evaluate obstetric outcome of second delivery inwomen whose first baby was macrosomic.

STUDY DESIGN: The obstetric outcome of second delivery of primiparouswomen whose first infant weighed >4.5 kg, delivering during the four years1997-2000 was analyzed. A control group of 300 consecutive women deliveringa first infant weighing 3.0-3.5 kg in 1997 was used for comparison.

RESULTS: Among 13,020 primiparas delivering during the study period, 301(2.6%) infants were macrosomic. A similar proportion in both groups- 52% ofmacrosomics and 57% of controls- returned for second delivery before 2004.Compared with controls, first macrosomic deliveries were characterised byhigher rates of instrumental (23% vs 16%; P = ! .01) and intrapartumcesarean delivery (23% vs 10.7%; P ! .01). At second delivery, recurrence ofmacrosomia was 102/156 (65%). 27 (9%) compared with 8 (3%) controlsunderwent prelabor cesarean and the intrapartum cesarean rate was significantlygreater than controls (14/129, [10.7%] vs 7/164 [4.2%], P ! .05). Among theprevious macrosomic group 103/104 women (99%) who labored following firstvaginal delivery had a subsequent vaginal delivery compared with 11/25 (44%)who labored after primiparous cesarean delivery (P ! .001). Similarly, 119/123(97%) of controls had a second vaginal delivery following primiparous vaginaldelivery compared with 7/10 (70%) following primiparous cesarean. Recurrencerates of macrosomia were similar (65% vs 64%) in vaginal and cesareandeliveries.

CONCLUSION: First vaginal delivery of a macrosomic infant was associatedwith a high (99%) incidence of second vaginal delivery, despite a two-thirdsrecurrence of macrosomia. Women who underwent primiparous cesarean withfetal macrosomia had a high risk of repeat intrapartum cesarean deliverywhether macrosomia recurred or not.

S154 SMFM Abstracts

546 TIMING AND COMPLICATIONS OF ABDOMINAL CERCLAGE: PRECONCEPTUAL VSANTEPARTUM PLACEMENT NICOLE SMITH1, THOMAS MCELRATH1, AVIVA LEE-PARRITZ2, 1Brigham and Women’s Hospital, Obstetrics and Gynecology,Boston, Massachusetts, 2Boston University, Obstetrics and Gynecology,Boston, Massachusetts

OBJECTIVE: Current literature supports the efficacy of abdominal cerclage,while reporting varying rates of complications. However, prior studies do notdistinguish between preconceptual and antepartum placement. This studycompares rates of surgical and pregnancy-related complications in these twogroups.

STUDY DESIGN: A retrospective case series was performed, including allwomen undergoing abdominal cerclage placement at Brigham & Women’sHospital from 1998-2003. We compared pregnancy history, intraoperativecomplications, and pregnancy outcome. Fisher’s exact and Student’s T testswere used for all comparisons.

RESULTS: A total of 28 women underwent abdominal cerclage placement.Results are summarized in the Table.

Comparison of indications and outcomes

PreconceptualN = 19

AntepartumN = 9 P value

Indications for cerclagePrior pregnancy of !24 wk 68%(13) 67%(6) .99Prior vaginal cerclage 68%(13) 56%(5) .67Prior cervical surgery 21%(4) 33%(3) .64

Operative complicationsNeed for transfusion 0 1 .33Post op temp O 100.4 0 1 .33Rupture of membranes N/A 1 -Pregnancy loss within 7 d N/A 2 -

Pregnancy outcomesNumber achieving pregnancy 9 9 .01Cunently pregnant 2 0 -GA O36 wk 5 6 .66Infants requiring NICU stay 0 0 1.00Second trimester loss 0 3 .07Cervical dilation despite cerclage 0 1 .30

CONCLUSION: This case review suggests that pregnancy complicationsresulting in second trimester loss were more common with antepartumplacement of abdominal cerclage. While preconceptual cerclage carries lesssurgical risk, not all women will go on to subsequent pregnancy, thus somelaparotomies may be performed unnecessarily. Patients must be counseled as tothe higher potential for fetal risk associated with antepartum placementcompared with the risk of unnecessary laparotomy and hospitalization withpreconceptual procedures.

547 EVALUATION OF THE MAXIMAL PRESSURE EXERTED BY OBSTETRIC FORCEPS ONA FETAL HEAD MANNEQUIN MODEL ALFREDO GEI1, KIMBERLY HENNAN2,VICTOR SUAREZ3, GARY HANKINS4, 1University of Texas Medical Branch atGalveston, Obstetrics and Gynecology, Galveston, Texas, 2University of TexasMedical Branch at Galveston, Obstetrics, Gynecology and ReproductiveSciences, Galveston, Texas, 3University of Texas Medical Branch atGalveston, Obstetrics and Gyneclogy, Galveston, Texas, 4University of TexasMedical Branch at Galveston, Obstretics & Gynecology, Galveston, Texas

OBJECTIVE: To quantify the maximal pressure exerted by the application ofdifferent forceps on a fetal head model.

STUDY DESIGN: Planar impressions of the following forceps blades wereobtained: De-Lee Simpson (DLS), Simpson-Luikart (SL), Kielland-Luikart(KL), Naegele (N), Tucker-McLane (TML) and Piper (P). Corresponding piecesof pressure-sensitive paper (350-1400 psi and 1400-7100 psi) were cut with 1 cmmargins from the blade’s edge and taped to the blade’s inner surface from theexterior portion of the forceps. For standardization, a single application wasperformed for 10 seconds by one of the authors. In all cases a symmetricbifronto-biparietal grip was used with the plane of the shanks kept at 2.5 cmbelow the anterior edge of the posterior fontanel and the handle closed to fullapposition. The developing sheets were separated from the blades and scannedwith a Fujifilm scanner to calculate the area of contact, maximal pressure,average force and a histogram of pressure. Comparisons were made betweendifferent instruments, fenestrated and non-fenestrated and right and left bladesusing Student’s t test, one way ANOVA and Tukey tests as appropriate.Significance: P ! .05.

RESULTS: Two sets of impressions per forceps per film were obtained. Thearea of contact between the blades and the head (above the film’s range ofdetection) averaged 0.06 sq. The highest pressure was exerted by the TM forceps(1531.4 G 27.4 psi) and the lowest by the LK (987.3 G 118.1 psi). The LKforceps generated significantly lower pressure than the N (P= .01), P (P = .02)and TM (P = .01) forceps. No differences were noted between fenestrated andnon fenestrated forceps, right or left blades or between different forcepsregarding average or maximal pressure, average force or area of contact. Nomeasureable impressions were recorded with the highest sensitivity paper (1400-7100 psi).

CONCLUSION: Biparieto-malar symmetric applications of commonly usedforceps on a fetal head mannequin model result in distal points of pressurereaching or exceeding 1000 psi.