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CONCLUSION: EFW10-19 as a screening tool for SGA increases thenumber of SGA neonates identified compared to EFW10 alone (falsepositive rate 9-12%). Fetuses with EFW10-19 are at increased risk ofsubsequent growth restriction and should be followed closely duringpregnancy.

357 Isolated abdominal circumference <5% is anndependent risk factor for small for gestational age infants

Amy Turitz1, Hayley Quant1, Nadav Schwartz1,ichal Elovitz1, Jamie Bastek1

1University of Pennsylvania Perelman School of Medicine, Maternal andhild Health Research Program, Obstetrics and Gynecology, Philadelphia, PA

OBJECTIVE: Evidence suggests that fetal abdominal circumferenceAC) �10% or �5% is associated with small for gestational age (SGA)eonates, but data are poor to support whether an isolated AC �5%AC5) in absence of estimated fetal weight �10% (EFW10) accuratelyredicts the development of subsequent EFW10, SGA �10%SGA10), or �5% (SGA5).

STUDY DESIGN: Retrospective cohort study (1/2008-12/2011) of allomen with singleton pregnancies 26-36 weeks and �1 growth scanerformed at our institution. Ultrasound-based weight was deter-ined by the Hadlock equation (1984) and percentile growth by thelexander growth curve. The association between isolated AC5 andFW10, SGA10, and SGA5 were compared using chi square analyses.dds of EFW10, SGA10, and SGA5 with AC5 were calculated usingVLR to control for confounders. Sensitivity (SN), specificity (SP),

ositive and negative predictive values (PPV, NPV) and areas underhe receiver-operator curve (AUC) of ultrasound parameters to pre-ict SGA10 and SGA5 were calculated.

RESULTS: The prevalence of isolated AC5 was 11.4%, EFW10 was.0%, SGA10 was 17.6%, and SGA5 was 8.3% (N�10,642). AC5 onrst growth scan (US1) was associated with a 4.0-fold increase (95%I 1.3-12.1) in the risk of EFW10 on subsequent ultrasound, a 6.0-fold

ncrease (95% CI 4.6-7.4) in SGA10, and a 5.4-fold increase (95%CI.1-7.2) in SGA5. EFW10 alone on US1 missed almost 70% of SGA10nd 56.5% of SGA5 infants. Isolated AC5 identified an additional6.0% of SGA10 and 20.8% of SGA5 neonates. Using both EFW10nd AC5 improved specificity and PPV compared to either parameterlone (Table). AUCs for EFW10 and AC5 to predict SGA were notlinically different and were only fair (10: 0.64 vs. 0.66, p�0.001; 5:.69 vs. 0.71, p�0.02).

CONCLUSION: Isolated AC5 as a screening tool for SGA increases thenumber of SGA neonates identified compared to EFW10 alone (falsepositive rate �5%). Fetuses with AC5 are at increased risk of subse-quent growth restriction and should be monitored closely duringpregnancy.

Test characteristics of EFW10 andEFW10-19 to predict SGA

NPV5, negative predictive value for SGA5; NPV10, negative predictive value for SGA10; PPV5, positivepredictive value for SGA5; PPV10, positive predictive value for SGA10; SN5, sensitvity to predict SGA5;SN10, sensitvity to predict SGA10; SP5, specificity to predict SGA5; SP10, specificity to predictSGA10.

Test characteristics for EFW10and AC5 to predict SGA

NPV5, negative predictive value for SGA5; NPV10, negative predictive value for SGA10; PPV5, positivepredictive value for SGA5; PPV10, positive predictive value for SGA10; SN5, sensitvity to predict SGA5;

2SN10, sensitvity to predict SGA10; SP5, specificity to predict SGA5; SP10, specificity to predictSGA10.

S158 American Journal of Obstetrics & Gynecology Supplement to JANUARY 2

358 Predicting infant and placental weight at birth (PLWB)sing customized models including first-trimester 3Dlacental volume, crown-rump length (CRL) andaternal characteristics

Anthony Odibo1, Alison Cahill1, Linda Odibo1, George Macones1

1Washington University in St. Louis, Obstetrics and Gynecology,t Louis, MO

OBJECTIVE: To determine if a combination of 3D placental volume,RL and maternal characteristics can be used to estimate infant birth-eight (BW) and PLWB.

STUDY DESIGN: A prospective study was performed of women withingleton pregnancies from 11 to 14 weeks. To evaluate placental vol-me (PV) 3D power Doppler was applied and the volume acquiredas analyzed using the Virtual Organ Computer-aided Analysis (VO-AL™) program by a reader blinded to pregnancy outcome. Coeffi-

ients for significant maternal variables, CRL and PV affecting fetalnd placental growth (growth potential at term) were obtained usingackward stepwise multiple regression. The predicted BW and PLWBere then compared with actual BW and placental weight. The pri-ary outcome was an absolute error between predicted BW and ac-

ual BW �500g, and between predicted PLWB and actual PLWB100g.

RESULTS: PV was rendered in 712 pregnancies. Significant variablesssociated with BW and their coefficients are shown in the Table.hese variables were used to predict the expected birthweight at term.he constant for the birthweight prediction model is: 3550g [standardrror (SE) 593g]. PV was significantly associated with PLWB with aonstant for the model of 409.2g (SE 10.6g). Of 569 patients deliveringt term, 53 (9.3%) had an absolute error �500g using predicted BW.f 149 patients with placental weight assessed at term, 15 (10.1%) had

n absolute error �100g using predicted PLWB.CONCLUSION: The findings suggest that placental weight and birth-weight can be predicted with good precision in the first-trimesterusing customized models combining 3D ultrasound and maternalcharacteristics.

359 MSAFP does not improve detection rate for open neuralube defects in patients who receive first- and early second-rimester ultrasounds for fetal anatomical survey

Ashley Roman1, Simi Gupta1, Nathan Fox2, Daniel Saltzman3,had Klauser3, Andrei Rebarber2

1New York University School of Medicine, Obstetrics and Gynecology, Nework, NY, 2Mount Sinai School of Medicine, Obstetrics and Gynecology,ew York, NY, 3Carnegie Imaging for Women, Maternal Fetal Medicine,

New York, NYOBJECTIVE: Maternal serum alpha-fetoprotein (MSAFP) is used todentify patients at high risk for open neural tube defects (ONTD).

any centers have started performing anatomical surveys during therst- and early second-trimester in addition to the routine 18-20 weekcan. This study evaluates whether MSAFP improves the detectionate of ONTD in patients undergoing first- and early second-trimesternatomical surveys.

STUDY DESIGN: A historical cohort of patients undergoing fetal ultra-ound in a single ultrasound practice between May 2005 and August

Variables and coeeficients usedfor birthweight prediction

CRL, crown rump length; GA, gestational age.

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lucency ultrasound with evaluation of the fetal anatomy at 11-14weeks AND an early second trimester fetal anatomical survey between15 and 17 weeks. All cases of ONTD diagnosed in our unit were iden-tified using ICD-9 codes, and all MSAFP results over the same timeframe were queried. Groups were compared using Fisher Exact testwith p�0.05 as significance.RESULTS: Our unit performed 17,656 nuchal translucency ultra-ounds and 21,436 early anatomical surveys, and sent 11,809 speci-

ens for MSAFP during the study period. 11 ONTD were diagnosedy our unit during this time frame (incidence of 0.56 to 0.67 per 1000).1/11 ONTD (100%) were diagnosed by ultrasound; 0/11 (0%) wereetected after MSAFP screening (p�0.0001). 7/11 cases (64%) wereiagnosed during the first trimester; 4/11 (36%) were diagnosed at thearly second trimester anatomy scan. No cases of ONTD were diag-osed after 18 weeks’ gestation, and no cases of ONTD were missed byur unit (sensitivity 100%).

CONCLUSION: Ultrasound for fetal anatomical survey during the firstand early second trimester detected 100% of ONTD in our populationwith the majority identified in the first trimester. MSAFP was notuseful as a screening tool for neural tube defects in the setting of thisultrasound screening protocol.

360 Does first-trimester ultrasound predict obstetrical andeonatal outcomes in monochorionic diamnioticwin pregnancies?

Baraa Allaf1, Ali Ozhand2, Sina Haeri3, Joseph Wax4, Anthonyintzileos1, Adam Borgida5, Martin Chavez1, Sarah Davis6,amadeh Ravangard7, Melissa Spiel7, Rebecca Habenicht8, Glennarkenson9, Manisha Gandhi4, Amir Shamshirsaz10, Paulgburn10, Marjorie Meyer6, Jeff Johnson8, Allison Sadowski7,inston Campbell7, Alireza Shamshirsaz3

1Stony Brook-Winthrop University Hospitals, Obstetrics and Gynecology, Longsland, NY, 2University of Southern California, Department of Preventive

edicine, Los Angeles, CA, 3Baylor College of Medicine, Obstetrics andynecology, Houston, TX, 4Maine Medical Center, Obstetrics and

Gynecology, Portland, ME, 5Hartford Hospital, Obstetrics and Gynecology,artford, CT, 6University of Vermont College of Medicine, Obstetrics andynecology, Burlington, VT, 7University of Connecticut, Obstetrics

and Gynecology, Farmington, CT,, 8Dartmouth-Hitchcock, Obstetrics andynecology, Concord, NH, 9Baystate Medical Center, Obstetrics and

Gynecology, Springfield, MA, 10George Washington University, Obstetricsand Gynecology, Washington, DCOBJECTIVE: To determine the associations of discordant nuchal trans-ucency (NT) or crown-rump length (CRL) measurements at the timef aneuploidy screening with adverse obstetrical and neonatal out-omes.

STUDY DESIGN: A multicenter, retrospective cohort study in 9 regionalperinatal centers in the United States from 01/2006 to 06/2011. Allmonochorionic-diamniotic (MCDA) twin pregnancies with two livefetuses at the 11-14 week ultrasound examination and serial follow-upultrasonography until delivery were included. Pregnancies withknown chromosomal abnormalities or major malformations were ex-cluded. The NT and CRL discordances were calculated as the differ-ence between the two fetuses expressed as a percentage of the largermeasurement. Composite obstetrical outcome included any of thefollowing: IUFD, twin-to-twin transfusion syndrome (TTTS), intra-uterine fetal growth restriction (IUGR) or preterm birth � 28 weeks.Composite neonatal outcome included any of the following: Apgarscore � 7 at 5 minutes, respiratory distress syndrome, intraventricularhemorrhage, necrotizing enterocolitis, early onset sepsis, or neonataldemise. Receiver operating characteristic (ROC) curves of NT andCRL discordance cut-offs were developed for the prediction of com-posite obstetrical and neonatal outcomes.RESULTS: A total of 180 twin pregnancies met inclusion criteria. Mean�SD) gestational age at delivery was 33 � 3.4 weeks. A total of 26.1%nd 32% of pregnancies were found to have adverse composite ob-

tetrical and neonatal outcomes, respectively. Adverse obstetrical out- n

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come included: TTTS in 14 (7.7%), IUGR in 19 (10.5%), IUFD in 13(7.2%) and preterm birth (�28 weeks) in 14 (7.7%). Neither ROCcurve was discriminating between NT or CRL discordance and theprediction of adverse composite obstetrical or neonatal outcome (Fig-ure).CONCLUSION: In our population, NT or CRL discordance in monocho-rionic-diamniotic twin pregnancies were not predictive of adversecomposite obstetrical or neonatal outcome.

361 Prediction of perinatal outcomes in monochorioniciamniotic twin pregnancies by early secondrimester ultrasound

Alireza Shamshirsaz1, Baraa Allaf2, Sina Haeri1, Ali Ozhand4,elissa Spiel3, Samadeh Ravangard3, Anthony Vintzileos2, Adam

orgida5, Glenn Markenson6, Joseph Wax7, Sarah Davis8, Amirhamshirsaz9, Rebecca Habenicht10, Manisha Gandhi1, Jeffohnson10, Marjorie Meyer8, Allison Sadowski3, Paul Ogburn2,

artin Chavez2, Winston Campbell31Baylor College of Medicine, Obstetrics and Gynecology, Houston, TX,2Stony Brook-Winthrop University Hospitals, Obstetrics and Gynecology,

tony Brook, NY, 3University of Connecticut, Obstetrics and Gynecology,Farmington, CT, 4University of Southern California, Department of

reventive Medicine, Los Angeles, CA, 5Hartford Hospital, Obstetrics andGynecology, Hartford, CT, 6Baystate Medical Center, Obstetrics andGynecology, Springfield, MA, 7Maine Medical Center, Obstetricsand Gynecology, Portland, ME, 8University of Vermont College of Medicine,

bstetrics and Gynecology, Burlington, VT, 9George WashingtonUniversity, Obstetrics and Gynecology, Washington, DC, 10Dartmouth-

itchcock, Obstetrics and Gynecology, Concord, NHOBJECTIVE: To determine the association of discordant abdominal cir-umference (AC), femoral length (FL), head circumference (HC), orstimated fetal weight (EFW) at time of early second trimester ultra-ound with adverse perinatal outcomes.

STUDY DESIGN: A multicenter, retrospective cohort study in 9 perina-al centers in the United States from 01/2006 to 06/2011. All mono-horionic-diamniotic (MCDA) twin pregnancies with two live fetusest early second trimester (16-20 weeks) ultrasound, and serial fol-ow-up ultrasonography until delivery were included. Pregnanciesith known chromosomal abnormalities or major malformationsere excluded. The AC, FL, HC or EFW discordances were calculated

s the difference between the two fetuses expressed as a percentage ofhe larger measurement. Composite obstetrical outcome included:UFD, twin-to-twin transfusion syndrome (TTTS), intrauterine fetalrowth restriction (IUGR) or preterm birth � 28 weeks. Composite

eonatal outcome included: Apgar score � 7 at 5 minutes, respiratory

ent to JANUARY 2013 American Journal of Obstetrics & Gynecology S159