Most common anomaly seen in fetus of mother taking lithium carbonate is:

Lithium effect on pregnant women: Lithium should not be used during pregnancy, especially in the first trimester, because of possible teratogenicity. It is known to cause Ebstein's anomaly, a cardiac abnormality. It is characterized by apical displacement of the tricuspid valve , often resulting in severe tricuspid regurgitation and marked RA enlargement .