I doubt you mean an "inverted uterus" you probably mean "retroverted uterus" which is much more common. An inverted uterus is a complication from delivery which is very painful and must be fixed right away.
A retroverted uterus can be caused by pregnancy, menopause, or another gyncological condition or it can be perfectly naturally occuring. It is where the uterus is simply tipped back towards the spine instead of forward towards the belly button. About 20% of women have it. Most of the time, women who have it feel no symptoms and it doesn't affect them.
Sometimes, women will feel pain during sex or menstruation, but that is rare.
and doggy style sex is better for women who have a retroverted uterus because of the angle the penis goes in. Don't ask me why I know that, just strange trivia.