LOW YIELD OF FETAL ECHOCARDIOGRAPHY WHEN NO SUSPICION OF HEART DISEASE BY REFERRING OBSTETRICIAN

Abstract

The latest statement of the American Heart Association on the diagnosis of fetal congenital heart diseases (CHD) recommended that in the presence of factors that increase the risk of CHD above 3%, a referral for a fetal echocardiogram should be done. In the last two decades, we have seen an increase in the number of indications to perform a fetal echocardiogram. There is consensus that a fetal echocardiogram is needed in high-risk situations or when heart disease is suspected. The benefits of referring moderate risk pregnancies has been questioned when no fetal heart malformation is suspected at the obstetrical screening. Our main objective was to determine the number needed to test (NNT) to detect CHD in pregnancies with risk factors, but without a suspected heart malformation after obstetrical screening. This project is nested within cohort study assessing the results of prenatal CHD screening in all pregnancies in Québec. We are reviewing all fetal echocardiograms done between 2012 and 2016 in the 4 pediatric cardiology divisions in Québec. This abstract pertains to the results of the two institutions with complete data to date. Each suspected CHD was categorized according to the International Paediatric and Congenital Cardiac Code. CHDs were further categorized as moderate/severe CHD (likely to required early intervention) and mild/insignificant CHD (unlikely to require early intervention). For each indication, we calculated the yield (% of positive) and the NNT (number of exams to detect one case). A total of 5 889 pregnancies had analysable data. Moderate/severe CHD was observed or suspected in 3.0 % of fetuses. The NNT for fetuses with suspected CHD at obstetrical screening was 2.9 for all CHDs and 3.3 for moderate/severe CHDs (see also the Table). When no CHD was suspected at obstetrical screening, the NNT increased significantly to 33 for all CHD and 143 for moderate/severe CHD. Common indications such as increased nuchal translucency, familial history of CHD, pre-gestational diabetes and exposure to medication had very low yield and high NNT. These preliminary results show that when no CHD is suspected during obstetrical screening, common indications for fetal echocardiogram have a low yield of identifying a significant CHD. The final results of the complete cohort will include post- natal data allowing calculation of obstetrical false-negative and evaluation of the impacts of the current referral pattern on healthcare resources.