Recurrent Uterine Incarceration in Pregnancy

To editor: Incarcerated gravid uterus is a rare complication of pregnancy, with an estimated incidence of 1 in 3000 to 10,000 pregnancies.[1,2] It is observed in approximately 15% of women in early pregnancy. In most cases, the uterus spontaneously returns to its normal position by 14–16 weeks of gestation; however, in a small subset of patients, the uterus becomes trapped between the sacral promontory and the pubic symphysis, preventing spontaneous correction.[3–6] Written informed consent was obtained from the patient for publication of this case and the accompanying images. No studies involving human participants were conducted by the authors in the preparation of this report. A 31-year-old woman, gravida 2 para 1, was admitted at 37 weeks of gestation for an elective cesarean section. At 8 weeks, ultrasound revealed a double uterus with the fetus located in the left uterine cavity. At 23 weeks (Supplementary Fig. 1, https://links.lww.com/MFM/A102), ultrasound showed the placenta extending 7.2 cm beyond the cervical internal os, while MRI revealed abnormal uterine positioning, with the cervix lying between the anterior abdominal wall and the uterus. By 30 weeks (Supplementary Fig. 2, https://links.lww.com/MFM/A102), ultrasound indicated breech presentation with the placenta on the lateral wall, its lower edge covering the cervical os. At 36 weeks (Supplementary Fig. 3, https://links.lww.com/MFM/A102), repeat magnetic resonance imaging (MRI) demonstrated extreme retroflexion: the uterine body was tilted posteriorly into the pouch of Douglas, with elongation of the cervix and vagina (~9 cm) displaced between the anterior abdominal wall and uterus. The placenta involved the fundus, anterior and posterior walls of the middle and upper uterine body, and the right posterior wall. Cesarean delivery was performed at 37 weeks. The lower uterine segment was located directly beneath the incision. Exploration revealed extreme retroflexion (~180°), with the posterior serosa adherent to the lower segment. A transverse incision near the uterine base was made to deliver a healthy male infant weighing 3215 g with Apgar score of 10. Following delivery, the uterus spontaneously returned to its normal shape and position. At the 6-week postpartum follow-up, two uterine cavities were still visible, suggesting a folded uterus that had not been restored. The patient had a notable obstetric history. In 2016, she underwent cesarean section for suspected placenta previa, which intraoperatively proved to be uterine torsion and incarceration. Multiple attempts at manual reduction failed. A uterine incision was made 5 cm above the fetal head, obliquely through the right uterine wall, ~2 cm from the cornua. Postpartum follow-up again revealed two uterine cavities, initially suspected to represent a septate uterus but later considered a persistent folded uterus. At that time, the patient was advised to avoid future pregnancy, but she did not comply. Various risk factors have been associated with uterine incarceration, including a history of pelvic or abdominal surgery, inflammatory conditions, endometriosis, abnormal uterine morphology, myomas in atypical locations, and structural anomalies of the pelvis (e.g., a deeper sacral promontory). The mechanism underlying recurrent uterine incarceration remains poorly understood, partly due to the limited number of reported cases. Recurrence may result from unresolved predisposing factors from a prior episode, such as an abnormally shaped uterus or pelvic adhesions caused by uterine scarring at the fundus. Notably, there are no reports in the literature regarding the effectiveness of manual reduction prior to pregnancy. Existing evidence suggests that uterine incarceration is uncommon in early gestation, as most cases spontaneously resolve once the uterus enlarges beyond the pelvic cavity. Clinically, patients typically present with urinary retention or pelvic discomfort after 16 weeks of gestation. In this case, the patient experienced uterine incarceration during her first pregnancy, with early ultrasound suggesting a septate uterus due to the presence of two apparent uterine cavities, which were in fact a single folded cavity. Notably, she did not exhibit urinary retention or abdominal pain during that pregnancy. Six weeks postpartum, ultrasound again suggested a septate uterus. During her subsequent conception, early pregnancy ultrasound continued to show a septate uterus, indicating that the folded uterus did not impede natural conception. Consequently, no manual or surgical reduction was performed during the early or mid-pregnancy stages; instead, the patient was closely monitored with ultrasound every two weeks and MRI monthly. Complications associated with an incarcerated uterus can include abnormal fetal positioning and altered uterine morphology, potentially leading to premature rupture of membranes, spontaneous abortion, or preterm delivery. The incarcerated uterus may displace the cervix anteriorly and compress the uterine body against the bladder, resulting in urinary tract inflammation and dysuria. Prolonged or excessive compression can further lead to myometrial necrosis, uterine rupture, or thrombosis.[1–3] We reviewed case reports published between 1991 and 2015, summarizing four cases in total (see Supplementary Table 1, https://links.lww.com/MFM/A102 for details).[7] Most patients underwent cesarean delivery, with the timing of delivery influenced by the presence or absence of clinical symptoms. Patients without complications generally delivered at later gestational ages and had favorable neonatal outcomes. Similar experiences have been reported in China. Gao et al.[8] summarized six cases of uterine incarceration managed at their hospital, of which four patients presented with lower abdominal pain. Notably, urinary retention was the initial symptom in all cases. Manual reduction was successfully performed after bladder decompression in each patient. Except for one case delivered by cesarean section due to complications, the remaining five cases underwent vaginal delivery. Fang et al.[9] reported a case of uterine incarceration in which the patient experienced abdominal pain and vaginal bleeding at 12 weeks of gestation. Ultrasound confirmed the diagnosis, and manual reduction was successfully performed vaginally at 16 weeks. The patient continued routine prenatal care and ultimately delivered vaginally at term. Based on the available international literature, the decision to perform manual reduction appears to depend on the underlying cause of uterine incarceration. In cases where incarceration results from uterine adhesions, scarring, or pelvic structural abnormalities, manual reduction may not be feasible. Conversely, for asymptomatic patients, including those without significant abdominal pain or urinary retention, routine manual reduction during pregnancy may be unnecessary. Diagnosis can be optimized through a combination of physical examination, ultrasound, and MRI, particularly when guided by characteristic symptoms and risk factors. Regardless of gestational age or symptom severity, cesarean section is generally the preferred mode of delivery. With timely and appropriate management, both maternal and neonatal outcomes are typically favorable. Acknowledgements We thank Li Wang for assistance of Ultrasound figures preparation. Funding None. Conflicts of Interest None. Data Availability The datasets generated during and/or analyzed during the current study are not publicly available, but are available from the corresponding author on reasonable request.