OP30.02: Crown–rump length discordance and fetal structural abnormalities in twin pregnancies

Abstract

Conclusions: Twin pregnancies with CRL discordance >10% are at increased risk of adverse perinatal outcome and should be considered high risk pregnancies. Therefore dating seems more appropriate based on the larger CRL. OP30.02Crown-rump length discordance and fetal structural abnormalities in twin pregnancies A. Khalil Elborai, R. Townsend, F. D'Antonio, N. Tahir, A.T. Papageorghiou, A. Bhide, B. Thilaganathan St George's Hospital, London, United KingdomObjectives: Crown-rump length (CRL) discordance is associated with an increased risk of adverse pregnancy outcome in twin pregnancies. However, its predictive accuracy is poor. Furthermore, most of the studies have excluded cases with fetal structural abnormalities or aneuploidy. The aim of this study was to investigate the performance of CRL discordance in the prediction of major congenital anomalies in twin pregnancies. Methods: A retrospective study of all twin pregnancies of known chorionicity from a single tertiary fetal medicine center over a 13 year period. The diagnosis of chorionicity was determined in the first trimester and confirmed by placental examination. Pregnancies with single or double loss at the time of the scan, complicated by twin-twin transfusion syndromes, twin reversed arterial perfusion or conjoined twins were excluded from the analysis. Logistic regression analysis and Receiver-operating characteristics (ROC) were performed to evaluate the contribution of CRL discordance in determining the risk of structural anomalies. Results: 911 twin pregnancies (241 MC and 670 DC) were included and 85 (9.3%) pregnancies were complicated by structural anomaly. Logistic regression analysis demonstrated that CRL discordance (adjusted OR 1.07; 95% CI 1.04-1.11, p < 0.001) and increased nuchal translucency (NT > 3.5mm, which is the 99th centile) (adjusted OR 5.52; 95% CI 2.12-14.38, p < 0.001), but not chorionicity (p = 0.633), were independently associated with the risk of structural anomalies. This significant association persists even after adjusting for individual fetal size (p < 0.001 for both). The area under the ROC curve was 0.61 (95% CI, 0.54-0.68). At a cut-off of CRL discordance of 10%, the sensitivity and specificity were 31.8% and 86.6%, while the + ve and -ve likelihood ratios were 2.36 and 0.79, respectively. Conclusions: CRL discordance is associated with an increased risk of congenital structural defects. However, its predictive value is suboptimal. OP30.03Second trimester ultrasound measures in prediction of birthweight discordance and SGA in dichorionic twins C. Vedel, L. Rode, A. Tabor Center of Fetal Medicine, Copenhagen University Hospital, Rigshospitalet, Copenhagen, DenmarkObjectives: We wished to examine the association between second trimester discordant ultrasound measures and birthweight (BW) discordance and risk of one twin being small for gestational age (SGA) in dichorionic twins. Methods: Ultrasound data (from 22 + 0 to 24 + 6 weeks) on twin pregnancies was extracted from Astraia from 2006 to 2008 from the Danish departme...