In the mist inferior aspect of the septum width averaged 1.2 mm thick in children and 1.8 mm thick in adults.
Overall mean by Transesophageal US
anterior region 2.56 ± 0.92 mm
fossa ovalis 1.89 ± 0.75 mm
posterior region 2.95 ± 0.97 mm
Links and References
Qadir et al Measurement of interatrial septal thickness by echocardiography in patients with moderate to severe rheumatic mitral stenosis undergoing percutaneous balloon mitral valvuloplasty Int J Cardiol Heart Vasc. 2018;22:35–38. Published 2018 Dec 9.
Sweeney et al The normal anatomy of the atrial septum in the human heart Am Heart J. 1979 Aug;98(2):194-9.