The uterine horns are far more prominent in other animals (such as cows[1] and cats[2]) than they are in humans.
In the cat, implantation of the embryo occurs in one of the two uterine horns, not the body of the uterus itself.
Occasionally, if a fallopian tube does not connect, the uterine horn will fill with blood each month, and a minor one-day surgery will be performed to remove it.
The spare egg, that cannot travel the fallopian tube, is absorbed into the body.
This article incorporates text in the public domain from the 20th edition of Gray's Anatomy (1918)