Retroversion of the uterus is found in approximately 11 to 19% of women at the time of conception . Usually the uterus assumes a normal position at about the twelfth week of pregnancy, when the expanding organ enters the abdomen. Retroversion only rarely persists after 14-16 weeks. If retroversion persists, the fundus becomes incarcerated in the pelvic cavity. Incarceration of the gravid uterus occurs in approximately one of 3000 pregnancies [1, 2]. Contributing factors can be pelvic adhesions, endometriosis, ovarian tumors, leiomyoma and uterus anomalies [2, 4, 6–10]. Early recognition of incarceration of a retroverted uterus is of high importance, because correction may still be possible and pregnancy can proceed normally.
The obstetrician should always consider the possibility of turning the uterus to an upward position . In the presented case, we considered turning the uterus in upward position, but no attempts were undertaken due to the late presentation, absence of symptoms and increased risk for premature labour.
Some authors suggest that patients carry more risk of recurrence of retroversion of the uterus . Our case report is the fourth case of recurrent incarceration of the gravid uterus in literature. One previous case, describes a woman with uterus didelphus , in the other two cases no plausible cause for the condition were found [9, 11]. We recommend that women with a history of an incarcerated retroverted gravid uterus, in later pregnancies should be examined early in pregnancy.
Retroversion of the gravid uterus presenting as late as in the third trimester been scarcely reported. According to Singh and co-workers, only 28 cases were reported in the English literature between 1967 and 2006 . Incarceration may lead to increased foetal mortality and maternal morbidity and diagnosis of uterine incarceration is difficult due to variable clinical manifestations, ultrasound findings and physical examination.
Clinical manifestations occur after the first trimester and can be divided into four categories;  Obstetric and gynaecological symptoms, e.g. bleeding, miscarriages due to compromised uterine circulation;  Pressure symptoms, e.g. lower abdominal pain;  Urinary symptoms, e.g. urinary frequency, dysuria, incontinence; and  Gastrointestinal symptoms, e.g. rectal pressure, tenesmus, constipation [2, 3, 10]. Only few cases are described where no obvious causes or symptoms were found [5, 7, 11], as in our case. Ultrasound examination may show a drawn up bladder along with absence of the anterior uterine wall. However, as in the presented case, ultrasound can be misleading. During the first pregnancy we didn't find signs that made us suspect distorted anatomy. Our patient was diagnosed with a foetus in breech position and a complete placenta previa by ultrasound. However, caesarean section revealed an incarcerated, retroverted uterus; hence the ultrasound based diagnosis was erroneous. Four past cases of uterus incarceration have described similar findings. Similar to the presented case, three cases describe spontaneous rupture of the membranes and oligohydramnios in the setting of placenta previa [4, 5, 13]. This unusual combination may therefore indicate a uterus incarceration.
Indicators for an incarcerated uterus at physical examination include low fundal height, a filled cul-de-sac and an unreachable cervix 2. The cervix wasn't palpable, but was visible with transvaginal ultrasound, during her first pregnancy the possibility of an incarcerated uterus was not considered. It was unknown whether the patient had a retroverted uterus prior to pregnancy. When uterus incarceration occurs, the cervix becomes displaced upward above the symphysis, making vaginal delivery impracticable. Two previous cases of vaginal deliveries resulted in foetal death [14, 15]. Therefore, if incarceration of a retroverted gravid uterus is suspected a caesarean section must be planned. Hence, preoperative recognition of retroversion is essential and can prevent intraoperative complications. Herein, it is of great importance to bear in mind that the distorted anatomy due to uterus incarceration can result in maternal morbidity. Previous cases note trauma to the bladder, vagina, and cervix as well as delivery through the posterior wall of the uterus [1, 5, 7, 12]. The current case illustrates the practical difficulties of this distorted anatomy, which resulted in two transvaginal caesarean sections. Transvaginal caesarean in the setting of retroverted incarcerated uterus has only scarcely been described. Uma and co-workers  described a patient with an incarcerated fibroid gravid uterus. They preformed a transvaginal caesarean section resulting in a completely detached uterus at the level of the vagina. Due to this complication, a hysterectomy was performed.
To our knowledge our case is the first case which describes two successful transvaginal caesarean sections. Still, in hindsight we wouldn't recommend a transvaginal caesarean section. Preoperative recognition of retroversion is essential and can prevent intraoperative complications.
Due to the incarceration of the uterus the cervix, vagina and bladder might become elongated. Localization of the elongated vagina, cervix, as well as the urethra and bladder are essential for surgery. Proceeding to caesarean section without correct diagnosis will cause difficulties identifying these structures and in opening the lower uterine segment. This may lead to bladder injuries, vaginal transsection and trans- or supracervical hysterectomy. Magnetic resonance imaging offers a non/invasive method to confirm the diagnosis and to reconstruct the exact anatomy . In this case we unfortunately did not think of this possibility. After this visualization of the anatomy we would recommend a median laparotomy and if possible, restoration of normal anatomy [1, 4, 12]. When normal anatomy cannot be restored, the incision in the uterus should if possible be made in the lower uterine segment, for this prevents future maternal morbidity. If this is not possible a high (corporal) incision is required.