3–7 September 2006, London, UK Oral communication abstracts OC20 Validation of a logistic regression model to predict the outcome of pregnancies of unknown location in a new patient population E. Kirk 1 , P. Alnaes-Katjavivi 2 , G. Condous 1 , B. Van Calster 3 , S. Van Huffel 3 , O. Istre 2 , D. Timmerman 4 , T. Bourne 1 1 Early Pregnancy and Gynaecological Scanning Unit, St George’s Hospital, University of London, United Kingdom, 2 Ulleval University Hospital, Norway, 3 Department of Electrical Engineering (ESAT), Katholieke Universiteit Leuven, Belgium, 4 Department of Obstetrics and Gynaecology, University Hospital Gasthuisberg, Katholieke Universiteit Leuven, Belgium Objectives: A logistic regression model, based on the hCG ratio (hCG 48 hours/hCG 0 hours) has previously been developed in the Early Pregnancy Unit of an inner London Hospital, to predict the outcome of pregnancies of unknown location (PULs). The aim of this study was to validate this model in a new patient population. Methods: Serum hCG levels at 0 and 48 hours were collected on women classified as PULs presenting to the emergency gynecology service of a large Norwegian hospital. The final clinical outcomes of the pregnancies were recorded. Data was entered into the model and sensitivities, specificities, positive predictive values (PPV) and negative predictive values (NPV) calculated for each of the pregnancy outcomes (failing PUL, intra-uterine pregnancy (IUP) and ectopic pregnancy (EP). Results: Data was collected on 100 PULs presenting between 01.01.05 and 10.05.05. The model predicted that there were: 36 failing PULs, 15 IUPs and 49 EPs. The true pregnancy outcomes were: 61 failing PULs, 21 IUPs and 18 EPs. The sensitivity for the prediction of EP was 88.9% with a specificity of 56.1%, a PPV of 32.7% and a NPV of 90.2%. The sensitivity for the detection of an IUP was 61.9%, with a specificity of 62.0%, a PPV of 86.7% and a NPV of 57.7%. The sensitivity for the detection of a failing PUL was 54.1%, with a sensitivity of 74.4%, a PPV of 91.7% and a NPV of 45.3%. Conclusion: This logistic regression model based on the hCG ratio can be applied to other patient populations to predict EPs in women classified as PULs. OC21 Comparison of nuchal scan and detailed morphology scan in the first-trimester screening for fetal structural abnormalities M. Chen 1 , Y. H. Lam 2 , C. P. Lee 1 , R. Tang 3 , B. Chan 1 , S. F. Wong 4 , H. Y. Tse 5 , M. H. Y. Tang 6 , K. Y. Leung 1 1 Department of Obstetrics and Gynaecology, The University of Hong Kong, Queen Mary Hospital, China, 2 Hong Kong Prenatal Diagnosis Center, China, 3 Department of Obstetrics and Gynaecology, Pamela Youde Eastern Hospital, China, 4 Department of Obstetrics and Gynaecology, Princess Margaret Hospital, China, 5 Department of Obstetrics and Gynaecology, Kwong Wah Hospital, China, 6 Prenatal Diagnostic and Counseling Department, Tsan Yuk Hospital, China Objective: To compare the effectiveness of nuchal scan at 11–14 weeks and detailed morphology scan at 12–14 weeks in the screening for fetal structural abnormalities. Methods: From March 2001 to November 2004, 8926 pregnant women were randomized into either the nuchal scan group (11–14 week NT scan followed by routine 18–23 week scan) or the detailed morphology scan group (detailed 12–14 week scan followed by routine 18–23 week scan). Results: 84 structural abnormalities from 7757 fetuses viable at the first-trimester ultrasound examination with known pregnancy outcome were analyzed. In the nuchal scan group, detection rate in the first trimester was 32.8% (21/64, 95% CI 21.6–45.7). The overall detection rate of structural abnormalities at the first and second trimester was 64.1% (41/64, 95% CI 51.1–75.7). Meanwhile, in the detailed morphology scan group, detection rate in the first trimester was 47.6% (30/63, 95% CI 34.9–60.6). The overall detection rate at the first- and second-trimester scan was 66.7% (42/63, 95% CI 53.7–78). The overall detection rate of first and second-trimester scan in the nuchal scan group did not significantly differ from that in the detailed morphology scan group (P > 0.05). Conclusions: In settings where nuchal scan is offered, a basic anatomical survey can be done in conjunction with the NT measurement. A detailed morphology scan at this early gestation may not be superior in screening for fetal abnormalities in the low risk population. The routine 18 – 23 week scan cannot be abandoned. OC22 Detection of fetal anomalies in the first and second trimesters A. Kang, H. Struben , W. Holzgreve, O. Lapaire, S. Doht, S. Tercanli UFK Basel, Switzerland Objectives: To evaluate the detection rate of fetal anomalies using first and second-trimester ultrasound. Methods: Ultrasound screening was performed in 6017 fetuses by well trained sonographers in a single ultrasound centre between 11 and 14 weeks of gestation, followed by a second-trimester ultrasound. The nuchal translucency (NT) was measured and risk calculation for chromosomal anomalies was performed in all cases. Additionally, all fetuses were explored for the presence or absence of concomitant anomalies. Fetal outcome was available in all cases. Results: The aneuploidy rate was 1.2% (n = 73), of which 60 cases (82%) were diagnosed by risk assessment using NT and maternal age. The incidence of fetal malformations (other than NT) was 2.7% (n = 161), of which 49% (79/161) were diagnosed between 11–14 weeks. The anomalies consisted of 16 cases of the central nervous system, 5 of the urinary tract, 8 of the cardiovascular system, 19 of the anterior abdominal wall and 9 of the skeletal system. Combining first and second-trimester ultrasound, the overall detection rate was 86% (139/161). 14% (22/161) of the anomalies were diagnosed in the neonatal period (such as microcephaly, spina bifida occulta, ASD, minor VSD < 2 mm, hexadactyly, unilateral club-foot, cleft soft palate). All cases of anencephaly and omphalocele were detected in the first trimester. Conclusion: There has been shown a tendency in the last decade to diagnose an increasing number of fetal anomalies between 11–14 weeks. Nearly half of the anomalies in the study group were diagnosed in this period. However the results demonstrated the necessity of a backup in the second trimester. Larger trials are needed to define specific groups of anomalies which should be diagnosed between 11–14 weeks, as shown in our preliminary results. OC23 What information on fetal anatomy can a single transabdominal first-trimester three-dimensional sweep provide? R. J. Benzie , D. E. V. Fauchon, D. Wye, R. Thavaravy Nepean Hospital, University of Sydney, Australia Objective: To determine how much of the fetal anatomy listed in The Fetal Medicine Foundation (FMF) Program software can be visualised using the stored data set of a single transabdominal three-dimensional volume sweep of the entire fetus between 11 to 13 weeks and 6 days gestation. Methods: A transabdominal three-dimensional volume sweep of the entire fetus was performed in the mid-sagittal plane. The data set was stored on the hard drive of the Voluson 730 Expert (GE Medical Systems) ultrasound machine and copied to a compact disc. It was then manipulated on the 4D View GE Medical Systems Kretz Ultrasound in Obstetrics & Gynecology 2006; 28: 359–411 365