Incarceration of the gravid uterus(IGU) is a rare obstetric disorder.With the pregnancy weeks increasing,the gravid uterus transforms from a pelvic organ to an abdominal organ. In most cases,the retroverted uterus spontaneously corrects itself as the fundus rising out of the pelvis forward to its normal anatomical position between 12-14 weeks of gestation.[1] On rare occasions, the uterus remains in a retroverted position as it enlarges, becoming trapped in the pelvis between the sacral promontory and the symphysis pubis（the Douglas pouch or the uterovesical pouch）,[2]this is called incarceration of the gravid uterus. If it is not treated timely, it will lead to severe complications such as premature rupture of membrane , miscarriage or even the rupture of uterus, bladder and renal failure. Therefore, early diagnosis is the key to reducing complications .