500 LATE PRETERM DELIVERY AND THE HIGH-FREQUENCY OF SPECIAL CARE NURSERYADMISSION KARIN FUCHS1, OMAR MAURICE YOUNG1, PHYLLIS GYAMFI2, CYNTHIAGYAMFI1, 1Columbia University Medical Center, New York, New York, 2ORCMacro, Applied Research Division, Atlanta, Georgia

OBJECTIVE: To determine the frequency of admission to special care nurseriesamong late preterm infants born between 34 0/7 and 36 6/7 weeks gestation.

STUDY DESIGN: This was a retrospective cohort study of all late preterm infantsdelivered at our institution between January 2005 and December 2006. Recordswere reviewed to determine the gestational age at delivery, birth data, and newbornadmission to either the newborn nursery or to a special care nursery (includingtransitional nursery or neonatal intensive care unit). Patients with major fetal mal-formations were excluded.

RESULTS: A cohort of 740 late preterm infants was identified of which 34%(255/740) were admitted to a special care nursery. Stratified by gestational age, 72%(109/151) of infants born at 34 weeks were admitted to a special care nurserycompared to 37% (87/238) at 35 weeks and 17% (59/349) at 36 weeks (p��0.001).A higher proportion of male infants (37%; 137/369) were admitted to a special carenursery than female infants (32%; 118/371) (p�0.123).

CONCLUSION: One third of late preterm infants were admitted to a special carenursery. The admission rate to a special care nursery decreased by 50% with eachcompleted week of gestation between 34 0/7 and 36 6/7 weeks. The findings warrantfurther investigation regarding the necessity and possible prevention of these latepreterm deliveries.

0002-9378/$ - see front matterdoi:10.1016/j.ajog.2007.10.502

501 ADDITIONAL ANOMALIES MODIFY ANEUPLOIDY RISK IN FETUSES WITHOMPHALOCELE RUSSELL MILLER1, DANNY WU1, DAVID MCLEAN1, ANNE VAN DERVEER1, LYNN SIMPSON1, 1Columbia University Medical Center, The Center for Pre-natal Pediatrics, New York, New York

OBJECTIVE: To determine whether the identification of additional malforma-tions modifies the risk of aneuploidy in the setting of prenatally-diagnosed ompha-locele.

STUDY DESIGN: A retrospective series of fetal omphaloceles was identifiedwithin the anomalies database at our tertiary-care referral center between January,2003, and July, 2007. Inclusion required documentation of a comprehensive fetalanatomical survey, the prenatal diagnosis of an omphalocele, and availability oflinked karyotype results. Cases that met inclusion criteria were reviewed for thepresence of anomalies detected during prenatal ultrasonographic evaluation in ad-dition to the omphalocele. The association between additional anomalies andkaryotype results was tested using Fisher=s exact test, assuming a significance levelof 0.05.

RESULTS: 42 cases of prenatally-diagnosed omphalocele were identified, ofwhich 31 (73.8%) had documented karyotype results. 7 (22.6%) cases were aneu-ploid: four trisomy 18, one trisomy 13, one trisomy 21, and one triploidy (69, XXX).Among included cases, 20 were complex omphaloceles (defined as possessing ad-ditional anomalies) and 11 were isolated omphaloceles. 7 of 20 (35%) complexomphaloceles were aneuploid, whereas no isolated omphaloceles were aneuploid.Of euploid cases, 54.2% possessed complex omphaloceles. A p of 0.029 was calcu-lated using Fisher=s exact test, thereby suggesting a relationship between additionalanomalies and karyotype in the setting of antenatally-diagnosed omphaloceles.

CONCLUSION: The detection of additional fetal anomalies appears to modifythe risk of aneuploidy in pregnancies complicated by omphalocele. In this cohort,all isolated omphaloceles were euploid.

0002-9378/$ - see front matterdoi:10.1016/j.ajog.2007.10.503

502 ULTRASOUND ESTIMATION OF BIRTH WEIGHT AND PREDICTION OF FDR INPREGNANCIES COMPLICATED BY GASTROSCHISIS KATHERINE GESTELAND1,LEONARDO PEREIRA1, STUART WEINER2, RICHARD BROTH3, 1Oregon Health & ScienceUniversity, Division of Maternal-Fetal Medicine, Portland, Oregon, 2Thomas Jef-ferson University, Philadelphia, Pennsylvania, 3Maryland Perinatal Associates,Rockville, Maryland

OBJECTIVE: To evaluate the role of ultrasound (US) in estimating birth weight(BWT) and predicting fetal growth restriction (FGR) in pregnancies complicatedby gastroschisis (GSC).

STUDY DESIGN: A retrospective review of GSC cases evaluated by US within 2weeks (w) of delivery at two University Hospitals from 1996-2007. Charts werereviewed for gestational age (GA) at last US, GA at delivery, BWT, AC and EFW bylast US. A corrected EFW (cEFW) was calculated by combining the US EFW with acorrection for normal anticipated interval growth. The mean percentile differencein BWT and cEFW was calculated. The prevalence of FGR (BWT �10%) and theability of US to accurately diagnose FGR were determined.

RESULTS: 56 cases were identified. US consistently underestimated BWTacross all GA (Fig 1) with a mean percentile difference of 10 � 7%. The meandifference did not vary by fetal gender, GA at last US (�37, �37 w), or AC �5% onlast US. FGR was present in 13 of 56 (23%) cases. US accurately diagnosed FGR in6/13 (46%) and misdiagnosed 14/43 (32%) as FGR.

CONCLUSION: Overall, US consistently underestimates birth weight in fetuseswith GSC. The rate of FGR is increased in GSC, however, may be misdiagnosed inup to 32% of cases.

0002-9378/$ - see front matterdoi:10.1016/j.ajog.2007.10.504

503 PROGNOSTIC INDICATORS IN TWIN REVERSED ARTERIAL PERFUSION SEQUENCE:DOES SIZE MATTER? STEPHANIE MANN1, MARK P. JOHNSON1, MARA ROSNER1, R.DOUGLAS WILSON1, MICHAEL BEBBINGTON1, 1Children’s Hospital of Philadelphia,Center for Fetal Diagnosis and Treatment, Philadelphia, Pennsylvania

OBJECTIVE: Evaluate factors that correlate with a risk of complications in TRAPsequence.

STUDY DESIGN: A retrospective chart review of patients with TRAP sequen-ce.The EFW of the parabiotic twin was calculated by summing the volume of thetorso and extremities. Assuming a tissue density 1ml/1g, volumes were directlyconverted to grams.The twin weight ratio (TWR) was calculated as the ratio be-tween the pump (i.e., “normal” fetus) and its parabiotic twin.Polyhydramnios wasdefined as a DVP � 8.0 cm. Elevated combined cardiac output (CCO) was definedas a value � 600 cc/kg/min. Data were analyzed using an unpaired T-test, chisquare, and V-square.

RESULTS: 39 pregnancies were identified with TRAP sequence. 8/39 weremonoamniotic. Karyotype information was available for 36 of the pregnancies; onewas abnormal [de novo 46,XX t(5/13)]. No pump twin was hydropic at the time ofinitial presentation. 17 gestations had a TWR � 0.7; 22 were � 0.7. There was nostatistical difference in polyhydramnios or CCO between these two groups at thetime of initial presentation. Parabiotic fetuses that had cranial structures (n�16)were more likely to have primitive hearts (6/16, P � 0.02). In these 6, the pump twindid not have an increased incidence of elevated CCO or polyhydramnios. 13/39pregnancies had no intervention. In this group, 8/13 pregnancies with a TWR lessthan 0.40 AND normal AF volume, normal cardiac output, and a parabiotic fetuswith no upper body development all survived and delivered at a median GA of 37weeks.

CONCLUSION: In our small series, TRAP sequence is associated with a 3% inci-dence of aneuploidy. TWR and/or elevated cardiac output did not correlate withhydrops or polyhydramnios in the pump twin at initial evaluation. However, we donot have serial data to determine if fetuses with TWR � 0.7 or elevated CCO wouldhave developed polyhydramnios or hydrops later in pregnancy. Our data also sug-gest that surgical intervention may be unnecessary if the TWR remains less than40% AND there is no polyhydramnios, elevated CCO, or upper body developmentin the parabiotic fetus.

0002-9378/$ - see front matterdoi:10.1016/j.ajog.2007.10.505

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