This may be an explanation to explore. You may have been told that you have a unicornuate uterus, or instead, you may have had a miscarriage and are concerned that a unicornuate uterus may be responsible. What exactly is this condition and what role may it play in pregnancy and miscarriage?
A unicornuate uterus is a type of congenital uterine abnormality (müllerian duct abnormality). It is smaller than a typical uterus (often about half the normal size and usually has only one functioning fallopian tube (rather than two). The other side of the uterus may have what is called a rudimentary horn.
If the rudimentary horn is not connected to the rest of the uterus and vagina, then a woman may experience very painful periods because the menstrual blood becomes backed up (since it is unable to flow out through the vagina.)
Imaging studies, such as hysterosalpingogram (HSG) or ultrasound, may indicate that a woman most likely has a unicornuate uterus.
Source: very well family