539 ELECTIVE LABOR INDUCTION AND LABOR PROGRESSION INNULLIPARAS JUN ZHANG1, JAMES TROENDLE2, ANJEL VAHRATIAN1,ANTHONY SCISCIONE3, MATTHEW HOFFMAN4, 1National Institutes ofHealth, Epidemiology Branch, Bethesda, MD 2National Institutes of Health,Biostatistics Branch, Bethesda, MD 3Newark, DE; 4Christiana Hospital,Newark, DE

OBJECTIVE: Why does elective induction of labor, especially with unfavor-able cervix, increase risk of cesarean delivery in nulliparous women? Is it due tophysician factors or abnormal labor progression or both? We compared laborprogression pattern (labor curves) in electively induced versus spontaneouslabor in term, singleton nulliparas.

STUDY DESIGN: From 2002-2003, there were 1307 deliveries withspontaneous labor (SP), 320 with elective induction (OX), and 237 with electiveinduction following cervical ripening (OX + CR) at the Christiana Care HealthSystem, DE. Foley catheter was the only method for cervical ripening, andoxytocin was the only method for induction. We examined labor progressioncm-by-cm of cervical dilation using an interval censored regression andadjusting for mother’s race, epidural use, fetal size, and gestational age.

RESULTS: 61%of womenwith SP used oxytocin for augmentation. Before 5cm, OX + CR group had significantly slower labor than SP and OX groups(Table). However, OX + CR group had similar active phase as the SP group. OXgroup had slightly faster active phase than the SP group, probably due tooxytocin use. Cesarean rate was significantly higher in the OX + CR group,which was partly due to large excess in the number of ‘‘dystocia’’ cases in earlylabor.

CONCLUSION: The pattern of labor progression differs substantially ininduced labor compared to that in spontaneous labor. Women with electiveinduction following cervical ripening may need more time before interventionis considered.

540 RANDOMIZED STUDY ON TWO DINOPROSTONE ADMINISTRATIONROUTES FOR CERVICAL PRIMING AND LABOR INDUCTION IN LOW-BISHOP PREGNANCY NICOLA STROBELT1, MARTA RATTI1, GIULIAZANI1, VIRGINIO MEREGALLI2, 1San Gerardo Hospital Monza, Universityof Milano-Bicocca, Ob/Gyn, Monza, Italy 2Ospedale Carate Brianza, Ob/Gyn, Carate Brianza, Milano, Italy

OBJECTIVE: Dinoprostone vaginal insert was compared to dinoprostonecervical gel in few studies, enrolling patients with different Bishop scores (BS),gestational ages (GA), and treatments in controls. Present study comparesvaginal insert to cervical gel in patients with low inducibility at term.

STUDY DESIGN: Prospective, multicenter, randomized trial, with parity-based randomization. Admission criteria: single pregnancy with BS of 0-4, GA 37-41.0 weeks, intact membranes, no previous CS or bleeding or abnormal CTG atadmission. Study patients (group A, 56 cases) maintained vaginal insert untillabor or PROM or for 12 hours. After 12 hours, patients with BS < 4 receiveddinoprostone vaginal gel for two administrations with 8-hour interval, patientswith BS >4 underwent amniorrhexis (AMX) and oxytocin infusion. Control arm(group B, 51 patients) received two 0.5-mg dinoprostone cervical gelapplications with 6-hour interval, with further management equal to that ofgroup A. Groups (A vs B) were comparable for nulliparity (61% vs 59%),admission median BS (3 in both), GA (39.1 wks in both), induction indications,and neonatal birthweight (3201 ± 479 vs 3163 ± 498 grams).

RESULTS: Second-line induction (vaginal PG or AMX or both) wasrequired in 52% group A patients vs 49% control patients. Group A patientsexperienced shorter induction-to-delivery time (920 ± 427 vs 1266 ± 740minutes, P < 0.01, Student’s t-test). Groups A ad B showed similar incidence ofabnormal CTG during labor (15.7% vs 10.4%, P = 0.63, chi-square),hypercynetic labor (29.4% vs 27.1%), CS (21.4% vs 21.6%), CS for fetal distress(12.5% vs 11.8%), and umbilical artery pH < 7.10 (4.9% vs 2.5%, P = 1.0,Fisher’s exact test).

CONCLUSION: Both methods require 50% of second-line inductionprocedures, but vaginal insert leads to delivery with a shorter latency time. Evenif both methods seem to be equally safe for the mother and the newborn, largerstudies should investigate neonatal outcome.

541

542

Median duration of labor progression (in min; comparison of OX vs SP andOX + CR vs SP *P < .05; **P < .01; ***P < .001; ^p = .06)

3 to4

cm

4 to5

cm

5 to6

cm

6 to7

cm

7 to8

cm

8 to9

cm

9 to10cm

Overallc/s

% c/s#5cm

SP 87 66 45 34 27 25 25 13% 33%OX 85 58 28 * 23 ^ 22 ^ 22 * 17% ^ 26%OX + CR 146 *** 118 *** 49 38 24 27 25 39% *** 52% *

December 2003Am J Obstet Gynecol

S206 SMFM Abstracts

THE RISK OF RECURRENT PRETERM BIRTH IS SIGNIFICANTLYHIGHER IN PATIENTS WITH A PREVIOUS HISTORY OF VERY EARLYPREMATURE DELIVERY ERIN CLARK1, MICHAEL S. ESPLIN1, ALISONFRASER2, ELIZABETH O’BRIEN3, GERI MINEAU4, MICHAEL W.VARNER1, 1University of Utah, Obstetrics and Gynecology, Salt Lake City,UT; 2University of Utah-Huntsman Cancer Institute, Population Sciences,Salt Lake City, UT 3University of Utah-Huntsman Cancer Institute,Population Sciences, Salt Lake City, UT 4University of Utah-HuntsmanCancer Institute, Oncological Sciences, Salt Lake City, UT

OBJECTIVE: We hypothesized that the risk of recurrent PTB would besignificantly higher in women with a history of very premature PTB. Ourobjective was to quantify the risk of recurrent PTB in patients with a previoushistory of very early PTB.

STUDY DESIGN: The Utah Population Database was used to identify allwomen who had two or more deliveries in the state of Utah with the first birthoccurring between 1989 and 2001. The final database included 99,499 patientswho had 224,849 consecutive births. The relative risks for preterm birth werecalculated based on the gestational age of the previous delivery.

RESULTS: The Table depicts the rate of recurrent PTB for the 2nd birthbased on the GA of the 1st delivery. Although the rate of recurrent PTB < 32weeks was 15.9% in the next birth, the rate of recurrence fell to 7.1% in the thirdbirth and 2.8% in the fourth birth. The relative risk of PTB < 32 weeks’ gestationin the second pregnancy was significantly higher among women with a history ofPTB at < 32 weeks (RR = 27.2) as compared with women with a previous PTB at32-33 weeks (RR = 5.95).

CONCLUSION: Patients have recurrent PTB at approximately the sameGAas their previous PTB, suggesting that the etiologies for PTB differ at early vslater gestations. Although patients with prior PTB have a substantial recurrencerisk, they can be reassured by the fact that a majority subsequently deliver at ornear term. Individuals with subsequent term deliveries have an even betterprognosis.

Rates of PTB in live birth 2 based on gestational age of live birth 1

Live birth 1 < 32 wks 32-33 wks 34-36 wks >36 wks

<32 wks 15.9% 4.5% 18.8% 60.8%32-33 wks 3.5% 11.3% 19.6% 65.6%34-36 wks 1.9% 2.1% 21.0% 75.0%

FACTORS ASSOCIATED WITH PRETERM BIRTH DIFFER DEPENDINGON THE DEGREE OF PREMATURITY AT THE TIME OF DELIVERY ERINCLARK1, MICHAEL S. ESPLIN1, ALISON FRASER2, ELIZABETHO’BRIEN2, GERI MINEAU3, MICHAEL W. VARNER1, 1University of Utah,Obstetrics and Gynecology, Salt Lake City, UT 2University of Utah–HuntsmanCancer Institute, Population Sciences, Salt Lake City, UT; 3University ofUtah–Huntsman Cancer Institute, Oncological Sciences, Salt Lake City, UT

OBJECTIVE: We hypothesized that the underlying etiologies of pretermbirth (PTB) would vary based on the gestational age of the PTB. Our objectivewas to identify and compare the factors associated with PTB at < 32 weeks’, 32-33weeks’, and 34-36 weeks’ gestation.

STUDY DESIGN: The Utah Population Database was used to identify allwomen who had two or more deliveries in the state of Utah with the first birthoccurring between 1989 and 2001. The final database included 99,499 patientswho had 224,849 consecutive births. Stepwise logistic regression was performedto identify the factors most associated with preterm at < 32 weeks’, at 32-33weeks’, and at 34-36 weeks’ gestation.

RESULTS: See Table.CONCLUSION: The factors most associated with PTB <32 weeks were

different than those associated with a recurrent PTB at 32-33 weeks or at 34-36weeks, suggesting that very premature PTB may have different etiologies thanPTB at > 33 weeks’ gestation. A history of PTB at < 32 weeks is a much strongerrisk factor for subsequent PTB < 32 weeks as compared with previous PTB atlater gestational ages. However, a previous PTB at 32-33 weeks’ gestation was thestrongest risk factor for a subsequent PTB at 32-33 weeks and was even strongerthan a previous history of PTB < 32 weeks. The degree of prematurity of previousPTB must be considered when counseling patients about recurrence risks.

Odds ratios for factors associated with preterm birth (all confidence intervalswere significant to P < 0.01)

Factor PTB < 32 wks PTB 32-33 wks PTB 34-36 wks

Previous PTB <32 wks 13.00 9.33 5.52Previous PTB 32-33 wks 2.81 13.04 6.97Previous PTB 34-36 wks 1.55 1.96 4.90Placental Abruption 13.17 11.88 7.18Cervical Incompetence 6.12 5.55 3.51Eclampsia 4.33 3.83 3.38Maternal Substance Abuse 3.87 4.07 3.30Abnml Fluid (poly/oligo) 3.68 3.33 2.59Placenta Previa 2.81 3.93 5.43Chronic HTN 2.95 2.41 2.11Gestational Diabetes NS 2.08 2.79Any Uterine Bleeding 2.91 2.65 1.87Febrile Illness 2.10 1.78 1.10Pregnancy Assoc HTN 2.05 2.41 2.36Maternal Tobacco Use 1.54 1.52 1.41Preexisting Diabetes NS NS 1.70Maternal Renal Disease NS NS 1.22Rh Isoimmun NS NS 1.15