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www.AJOG.org SMFM Abstracts

55 FETAL THYMIC INVOLUTION CAN BE USED AS AN INDICATOR OF INTRAUTERINEINFECTION IN PATIENTS WITH PRETERM PREMATURE RUPTURE OF MEMBRANES(PPROM) JOAQUIN SANTOLAYA-FORGAS1, JUAN DELEON2, FRANCISCO GAMEZ2,RICARDO PEREZ2, EUGENIA ANTOLIN2, PILAR PINTADO2, LUIS ORTIZ2, 1Harvard MedicalSchool, Brigham and Women’s Hospital, Boston, Massachusetts, 2Hospital Grego-rio Maranon, Madrid, Spain

OBJECTIVE: Our aim was to determine if fetal thymus size is a useful indicatorof intrauterine infection in patients with pPROM

STUDY DESIGN: The fetal thymus was measured sonographically in patientswith singleton pregnancies �34 W with pPROM not in labor managed conserva-tively. Induction of labor was considered after 34 weeks if labor or chorioamnionitishad not developed. Placentas/amniotic membranes were evaluated and chorioam-nionitis diagnosed if PMN-leukocytes were seen in the chorion/amnion/umbilicalcord, or in significant amounts within the subchorionic space. Neonatal sepsis wasdiagnosed on clinical grounds with a positive blood culture. Thymic measurementswere plotted on a nomogram derived from 549 normal fetuses and considered smallwhen �5th percentile for GA. Differences in outcome variables between groupswere determined by the Student=s t-test. P� 0.05 was considered significant

RESULTS: 29 patients entered the study. Mean GA at ultrasound was 28.8 W,latency period 16 days, GA at delivery 31.1 W and newborn weight 1,656 grams. 11fetuses (39,3%) had a small thymic diameter and 8 (28,6%) a small perimeter. Nodifferences were noted between groups for standard fetal biometry, maternal age,parity, administration of antenatal steroids, length of latency period, infants= sex,mode of delivery, or 5 minute Apgar scores. Figure 1 shows efficiency of a smallthymus for prediction of chorioamnionitis and sepsis

CONCLUSION: These results suggest that measurements of the fetal thymuscould be used for detection of intrauterine infection in patients with pPROM

0002-9378/$ - see front matterdoi:10.1016/j.ajog.2008.09.383

56 TIMING OF DELIVERY FOR MONOCHORIONIC VS DICHORIONIC TWINS JON BARRETT1,ORI NEVO1, ANDREA LAUSMAN1, SHARON MASLOVITZ2, 1University of Toronto, To-ronto, Ontario, Canada, 2University of Toronto, Tel Aviv, Isael, Israel

OBJECTIVE: The optimal timing of delivery for monochorionic (MC) twins iscontroversial. Delivery by 36 weeks gestation has been suggested in order to reducethe risk in MC as compared to dichorionic pregnancies (DC). This study comparesthe outcome of uncomplicated MC to a DC twins that have reached 34 weeks.

STUDY DESIGN: A cohort of MC vs DC twins were followed in a universityhospital twin clinic. DC twins were seen at 12, 18, 24, 30 and 34 weeks. MC twinswere seen every 2 weeks. After 34 weeks, timing and method of delivery was decidedupon by referring physician. Outcome measures were gestational age (GA), birthweight (BW), Apgar score, method of delivery, admission to NICU, ventilation andSB/NND rate. MC/MA twins were excluded. Chi sq analysis using SPSS was used.

RESULTS: 273 DC twins and 133 MC twins were analysed. The mean birthweight was significantly lower in the MC (2018 g) vs DC twins (2326 g) ( p�.05).There was no difference in IUGR (4.8% vs 6.7%). More MC twins were delivered �37 weeks gestation 82 (61%) vs DC twins 46 (17%) ( p�.001). More MC 83 (63%)were delivered by elective CS vs 103 (38%) DC twins. (p�0.01). There was nodifference in the rate of SVD (71% vs 76%) in women who had trial of labor. Theincidence of low Apgar score at 5 minutes was the same (0.4% vs 0.5%). There wasno difference in the neonatal or stillbirth rate. The incidence of NICU admission(21% vs 7.9%) and ventilation (13.6% vs 3.8%) was significantly increased in MC vsDC twins ( p�.001).

CONCLUSION: This study reveals that early delivery of MC twins by elective CShas become established in a twin population. This results in an increase in themorbidity of MC vs DC twins expressed in an increase in NICU admissions, ven-tilation and CS. Planned vaginal birth in MC twins is likely to be as successful as inDC twins. The practice of early and operative delivery for MC twins needs to bere-evaluated.

0002-9378/$ - see front matterdoi:10.1016/j.ajog.2008.09.384

Supplemen

57 THE NATURAL HISTORY OF MONOCHORIONIC DIAMNIOTIC PREGNANCY NICOLESMITH1, CAROL BENSON2, KATHERINE ECONOMY2, JOAQUIN SANTOLAYA2, LOUISEWILKINS-HAUG2, DAVID ACKER3, JULIAN ROBINSON4, 1Brigham and Women’s Hospital,Obstetrics and Gynecology, Boston, Massachusetts, 2Brigham and Women’s Hos-pital, Massachusetts, 3Brigham & Women’s Hospital, Department of Obstetricsand Gynecology, Boston, Massachusetts, 4Brigham and Women’s Hospital, Bos-ton, Massachusetts

OBJECTIVE: To elucidate the natural history of monochorionic diamniotic twinpregnancy

STUDY DESIGN: Retrospective review of monochorionic diamniotic twin preg-nancies that had ultrasound evaluations after 14 weeks gestation at Brigham andWomen=s Hospital between the years 2001 and 2008.

RESULTS: 419 monochorionic diamniotic twin pairs were evaluated. Of these,322 delivered after 24 weeks gestation and 304 (94%) resulted in 2 survivors, 16(5%) resulted in 1 survivor, and in 2 (0.06%) there were no survivors. In sixty otherpregnancies, both twins died, were lost to follow up, or terminated prior to 24 weeksgestation. The overall rate of twin to twin transfusion syndrome (TTTS) was 17.9%(75), and 15.9% (57) delivered after 24 weeks. Twelve placental vessel laser abla-tions and 7 cord ligations were performed. Of the 419 pregnancies, 33 had a fetaldemise at a mean age of 21.4 weeks (95% CI 19.9-22.9) with 5 (15.2%) of themoccurring after 24 weeks GA. Twenty-two (64.7%) of these losses could be associ-ated with TTTS. In 14, both fetuses were lost, including 3 after cord ligation. 4fetuses were lost after laser ablations. After a single demise, 14 pregnancies werefollowed to delivery, which occurred at a mean of 11.8 weeks (95% CI 7.4-16.4) afterdemise, and at a mean GA of 35 weeks (95% CI 33-37). The mean GA of all livebirths was 33.9 weeks (95% CI 33.5-34.3).

CONCLUSION: Although a retrospective study, this represents the largest reviewof the natural history of monochorionic diamniotic twin pregnancy reported todate. The rate of twin to twin transfusion syndrome is higher than that seen in otherlarge series, however, overall survival is better.

0002-9378/$ - see front matterdoi:10.1016/j.ajog.2008.09.385

58 RISK FACTORS FOR AORTIC DISSECTION IN THE PREGNANT WOMAN WITH MARFANSYNDROME AND MARFANOID SHINJI KATSURAGI1, NAOKO IWANAGA1, KEIKO UEDA1,KAORU YAMANAKA1, REIKO NEKI1, JUN YOSHIMATSU1, TOMOAKI IKEDA1, 1National Car-diovascular Center, Department of Perinatology, Suita, Osaka, Japan

OBJECTIVE: Aortic dissection is one of the severe complications of pregnancythat may lead to maternal death. We investigated the risk factor of aortic dissectionfor pregnant women complicated with Marfan syndrome and Marfanoid.

STUDY DESIGN: We retrospectively investigated 28 cases of Marfan syndromeand Marfanoid managed in the single institute during pregnancy from 1991 to2007. Aortic dissection was observed in 11 cases (group D (dissected)), and was notin 17 cases (group ND (not dissected)). The size of sinus of Valsalva, family historyof sudden death and aortic dissection, delivery mode, how to fulfill the criteria of theMarfan syndrome, FNB (fibrillin) gene analysis was performed in the two groups.

RESULTS: The means � SD of the maternal age and delivery weeks were 29.5 �3.0 and 30.1 � 2.0 (p�0.66), 37 � 3 and 36 � 2 (p�0.66), in group D and groupND, respectively. More cases in group D (7/11, 63.6%) were delivered by cesareansection than in group ND (3/17, 17.6%) (p�.05). There was no difference in ful-filling criteria of Marfan syndrome between the two groups. More cases were relatedwith family history of sudden death and aortic dissection in group D (6/10, 60%)than in group ND (4/12, 33%) without statistical significance. Increased size of thesinus of Valsalva ( 40mm) was observed in group D (4/4, 100%) than in group ND(3/12, 25%) (p�.005). Aortic dissection occurred before, during, and after preg-nancy in 3, 6, 1 cases, respectively. There was no maternal death in both groups. Thegene investigation was performed in 9 cases and FBN-1 was positive in 3/3 (100%)and 4/6 (67%), in groups D and ND, respectively (p�0.26).

CONCLUSION: The large size of the sinus of Valsalva was observed in the aorticdissection cases in the pregnant women complicated with Marfan syndrome andMarfanoid.

0002-9378/$ - see front matterdoi:10.1016/j.ajog.2008.09.386

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