Examination and Treatment for Repeated Implantation Failure

Also called a uterine malformation. Normally, the shape of the uterus is oval and the lumen is triangular, but some have a heart-shaped upper part (bicornuate uterus) and some have a partition inside (septal uterus) among other varations.
There are many cases of spontaneous pregnancy even with unusual uterine morphology, but surgery may need to be considered in cases where it is causing infertility or miscarriage. (Saravelos SH, et al. Human Reproduction Update. 2008 Vol 14, No.5, p415-29.)