PURPOSE:  This study aimed to explore the feasibility of implementation of the ISUOG 2013 guidelines on routine second-trimester examination of the fetal heart.
MATERIALS AND METHODS:  This was a prospective study in 357 women with singleton pregnancy undergoing their routine second-trimester scan. The fetal heart was examined using B-mode in different planes according to the guidelines. Potential maternal and fetal factors that can affect the rates of diagnostic-quality imaging for each of the recommended views were tested, using regression analysis. The intra- and interobserver agreement was analyzed in stored video loops.
RESULTS:  Most cardiac structures could be successfully examined with rates at or close to 100 %. Structures with a successful examination rate of ≤ 85 % included the ventricular wall fine details (55.2 %), tricuspid valve insertion (82.6 %), aortic root with clear walls (77.9 %), pulmonary artery walls (65.8 %) and clear view of the great artery walls (66.7 %). Common factors affecting the likelihood of successful examination of these structures included maternal BMI, skin-to-crux distance and the orientation of the cardiac axis. A post-hoc analysis indicated that a lack of pre-defined criteria for diagnostic quality was a constant reason for the interobserver variation.
CONCLUSION:  Most of the cardiac views can be consistently and reliably obtained, with maternal habitus being the primary factor limiting the quality of visualization. As offline interpretation may be subjective, using pre-defined quality criteria for the assessment of the images might improve interrater agreement.