P05.01: Is the nuchal index increased in fetuses with congenital structural heart defects? A prospective study

Abstract

Objectives:To determine if the Nuchal Index (NIx) is increased in euploid fetuses diagnosed with an isolated structural congenital heart defect (CHD) on fetal echocardiogram. Methods: A prospective case-control study was conducted from March 2002 to July 2003. All patients between 18 and 24 weeks' gestation referred for fetal echocardiography were approached for participation. Patients were excluded if other major anomalies or an abnormal karyotype were present. The NIx was calculated as the mean nuchal thickness/mean biparietal diameter × 100. Fetal cardiac axis was calculated from hard copy images in a blinded fashion. Analysis was by standard descriptive tests, 2-tailed t-test, receiver operating characteristic (ROC) curve, univariate analysis and discriminant analysis. Cases were classified as normal or abnormal as per the co-authors diagnosis at the time of the fetal echocardiogram. Results: Of the 607 echocardiograms performed, 314 were eligible. Two hundred and seven (22 abnormals and 185 normals) were recruited for a capture rate of 65.9%. The mean NIx in the abnormal and normal group was 9.3 and 7.8 respectively. This was statistically significant (p = 0.003). Using a cut-off of 10.4 at a 5% false positive rate, the sensitivity was 29% with an ROC of 0.699 [95%CI 0.582, 0.816]. Eleven of the 22 abnormal hearts and 7/185 normals had an abnormal cardiac axis. (OR 0.04 [95%CI 0.01, 0.12, p < 0.00001]). Although NIx and Nth were different between the study groups, discriminant analysis was unable to identify an adequate cut-off to allow adequate prediction of CHD. Conclusions: The NIx and CA were significantly different in fetuses with CHD in a high-risk population. However, an appropriate cutoff value could not be found in our study. Further studies in a low-risk population are warranted. P05.02 National database for fetal cardiac anomalies in 2004