Uterine rupture, the rupture of the uterine body or lower segment of the uterus, can occur during late pregnancy and delivery. It is the most severe complication in obstetrics and may endanger the safety of the fetus and mother. The most common risk factors for uterine rupture include a history of uterine surgery, blocked decline due to cord prolapse, and improper use of uterine contraction drugs. Nevertheless, spontaneous uterine rupture also occurs in late pregnancy without associated risk factors. A study published in 2015 reported incidences of ruptured uteri among unscarred and scarred uteri with the results showing 4.54 and 28.60 per 100,000 deliveries, respectively (1).

Adenomyosis is a benign uterine disease characterized by invasion of the endometrial glands and stroma in the myometrium (2). It occurs in women of reproductive age and peaks between 30 and 50 years, and epidemiology shows that the incidence is between 7 and 50% (3).

The incidence of premature birth, uterine rupture, and other obstetric complications with adenomyosis are significantly higher than that in healthy women (4). This is related to the rupture of the myometrium and loss of muscle fibers in muscle cells, resulting in reduced uterine elasticity (5).

The traditional treatment for adenomyosis is hysterectomy, which is often considered the only solution for pain relief. However, due to the higher incidence of adenomyosis and patients' demands for fertility, hysterectomy is not a suitable treatment option for all patients. Several studies have reported various surgical methods, including laparoscopic partial adenomyosis resection and uterine trilobectomy (6). However, the risk of late uterine rupture in postoperative pregnancy is significantly higher (7). Therefore, the development of high-intensity ultrasound ablation (HIFU) offers the hope of preserving fertility.

HIFU has been widely used in gynecological patients with uterine fibroids and adenomyosis. The application of HIFU in the treatment of adenomyosis is well-established, and several studies report that ultrasound ablation can achieve the ablation of lesions and alleviate symptoms in patients without increasing the incidence of obstetric complications in subsequent pregnancies (8, 9).

However, a recent case of adenomyosis in our hospital presented with uterine rupture in the third trimester after HIFU therapy.

In 2012, the patient delivered a child via cesarean section without complications. In 2014, she visited our hospital with dysmenorrhea accompanied by increased menstrual volume. The dysmenorrhea score (Visual Analog Scale/Score, VAS) was seven, and the menstrual volume increased to double the previous menstrual volume. Magnetic resonance (MR) examination in our hospital indicated adenomyosis, which was located in the posterior wall of the uterus, with a size of 58 × 56 × 49 mm (Figure 1). Preoperative blood routine examination, coagulation function, liver and kidney function and electrocardiogram results were normal. Due to the symptoms of increased menstrual volume, the patient underwent endometrial biopsy first. Pathology revealed that the patient did not have endometrial cancer. The patient underwent HIFU at our hospital. The practical energy was 400 W, and the treatment time was 867 s. Postoperative MR (Figure 2) showed that the non-perfused area of the posterior uterine wall lesion was 59 × 40 × 43 mm, and the non-perfused volume ratio was 63.76%. After HIFU therapy, the patient was treated with gonadotropin-releasing hormone for 6 months; the dysmenorrhea score was reduced to one point when the drug was discontinued, and the menstrual volume returned to normal. However, postoperative MR images (Figure 3) showed a filling defect in the serosal layer of the posterior wall of the uterus, suggesting that ablation of the lesion broke through the serosal layer, which may lead to a serosal defect of the uterus. The patient was followed up regularly, and no enlargement of the adenomyosis lesion was found on reexamination.

This, now 34-year-old woman, conceived naturally in July 2020, and regular prenatal examinations showed normal fetal development and no apparent abnormalities in the uterus. On February 03, 2021, at 34 weeks of gestation, the patient presented with sudden dizziness, fatigue, decreased fetal movement, no fainting, nausea, vomiting, abdominal pain, vaginal bleeding, and no vaginal discharge. She was admitted to the hospital.

Physical examination showed the following: temperature 36°C; pulse rate, 94 bpm; resting heart rate, 25 beats/min; and blood pressure, 85/40 mmHg. We noted abdominal distention, abdominal softness, no tenderness, and no rebound pain. Ultrasonography indicated a single intrauterine pregnancy, the fetus was alive, and the fetal heart rate was low at 70 bpm. Emergency cesarean section was performed, and a baby boy was delivered successfully with an Apgar score of 3-6-6. During the operation, a large amount of blood was found in the pelvic and abdominal cavities (~2,500 ml), and a 12 × 6 cm rupture through the whole uterine wall was observed in the posterior wall (Figure 4). The uterine rupture location was consistent with the breakthrough position of the uterine serosal layer, as suggested by MR after HIFU surgery in 2014. The patient underwent surgery to repair her uterus. A total of 800 ml of concentrated red blood cells were transfused postoperatively. The patient and the neonate recovered well and were discharged 28 days after neonatal treatment.

Ethical review and approval was not required for the study on human participants in accordance with the local legislation and institutional requirements. Written informed consent from the [patients/ participants OR patients/participants legal guardian/next of kin] was not required to participate in this study in accordance with the national legislation and the institutional requirements.

SW was the patient's chief physician and was responsible for the patient's follow-up. This article has been modified by YH. LJ performed a cesarean section on the patient. JL and LY performed the HIFU on the patient. All authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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