22-year-old primigravida, with no family history of congenital heart disease or teratogenic drug intake, normal systemic examination and per abdomen corresponding to 35-36 weeks was referred to routine antenatal ultrasonography at 33 weeks of gestational age.
On ultrasonography, uterus showed a single live intrauterine foetus in longitudinal lie with cephalic presentation. The growth parameters were corresponding to the gestational age except for abdominal circumference which measured 4 weeks more than gestational age due to gross fetal ascites (Figure 3). Amniotic fluid was mildly increased for gestational age with an amniotic fluid index of 18 cm.
Excessive subcutaneous oedema was noted in head and neck region with resultant increased nuchal fold thickness of 10 mm (Figure 3). Bilateral pleural effusion with pericardial effusion was noted.
Foetal heart appeared enlarged, almost occupying the chest cavity. On four-chamber view, severe aneurysmal dilation of right atrium was seen associated with inferior displacement of septal and posterior leaflets of tricuspid valve with increased velocity across the valve of 85 cm/sec (Figure 2). Atrialisation of right ventricle was seen (Figure 1), suggestive of Ebstein anomaly with hydrops foetalis.
Ebstein anomaly is a rare form of cyanotic congenital cardiac anomaly accounting for less than 1% of all congenital heart diseases. It is one of the common malformations of the tricuspid valve . it is characterised by inferior displacement of septal and posterior leaflets of tricuspid valve associated with right ventricular and right atrial abnormalities . It is known to have very high perinatal mortality of about 85 % with a risk of spontaneous intrauterine death of 48% and neonatal mortality of 35% due to combination of hypoxia and severe congestive heart failure whereas tricuspid valve dysplasia has benign course, and it needs to differentiate from the former for proper management . Hence antenatal diagnosis has high level of clinical significance and antenatal fetal ultra sound and echocardiography are known to high-level accuracy in detecting it and the four-chamber view can identify intra cardiac abnormalities such as Ebstein's anomaly and tricuspid valve dysplasia. We report a case of antenatal diagnosed case of Ebstein anomaly during a routine obstetric ultra sound at 33 weeks of gestation.
It is characterised by defective development of tricuspid valve leaflets and chordae tendinae and papillary muscles arising from right ventricle. Valvular leaflets are not attached to their normal location at the annular ring, but displaced inferiorly, reducing the effective right ventricular cavity and atrialisation of right ventricle. While the anterior leaflet is rarely displaced from the atrioventricular annulus, severe tricuspid malformations show a spiral conformation, with the posterior leaflet being posterior and inferior from the septal leaflet. The septal leaflet is almost always displaced. Ebstein's anomaly is most common cause of tricuspid regurgitation and cardiac dysfunction in utero, resulting in fetal cardiomegaly, heart failure, pulmonary hypoplasia, hydrops and tachyarrhythmia .
Fetal echocardiography has a very sensitivity (91.6%) and specificity (99.9%) in antenatal diagnosis of congenital heart disease in high risk pregnancies .
Right ventricle is divided into proximal thin-walled 'atrialised' right ventricle and distal small trabecular functioning portion having a thick wall. It is commonly associated with atrial septal defects and anatomical or functional pulmonary atresia and rarely with ventricular septal defect 
Early presentation of the anomaly is associated with poor prognosis, early detection is very important in assisting the obstetricians in deciding on the termination of pregnancy, intra uterine progression of Ebstein anomaly is indicated by presence of hydrops foetalis and pulmonary hypoplasia, presence of other cardiac anomalies and discordant cardiac contractility.
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