Retroverted<unk>  is a normal variant (up to 20% of the population).
During pregnancy, a retroverted<unk>  spontaneously flips to become anteverted at 14-16 weeks gestation age.<unk>  = impregnated retroverted<unk>  that is unable to spontaneously revert because the fundus is wedged below the sacral promontory.
Growth of<unk>  during pregnancy in retroverted position leads to compression of pelvic organs leading to symptomatology.
Incarcerated uterus
The same abdominal pain differential as non-pregnant patients, plus:
Vaginal foreign body
Ectopic pregnancy
Tubo-ovarian abscess
First trimester abortion
Testicular trauma
Complete abortion