Spontaneous regression of a giant uterine leiomyoma after delivery: a case report and literature review

Uterine leiomyomas are the most common benign uterine tumors that are hormone-dependent. Approximately 50-77% of women suffer from uterine leiomyomas [1]. Uterine leiomyomas gradually shrink in postmenopausal women due to hormonal changes, while they typically exhibit gradual growth during the reproductive years.The influence of pregnancy on the size of uterine leiomyomas is unclear. But most literatures suggest that pregnancy has no effect on the size of uterine leiomyomas, which may cause uterine fibroid enlargement during the first trimester and uterine fibroid shrinkage or stabilization during the second and third trimesters. During puerperium, the majority of studies reported a size reduction or no changes of Uterine leiomyomas [2, 3]. This is a rare case report of a woman with multiple uterine leiomyomas (the largest leiomyoma measuring > 8.0 cm) who experienced complete regression of the submucosal and multiple intramural leiomyomas more than 3 years postpartum.

The patient was a 40-year-old female, gravida 6, para 1, with a history of cesarean section. On December 14, 2018, an ultrasound examination (Fig. 1a) revealed multiple masses of medium-to-low echogenicity in the myometrium of the uterus, suggestive of leiomyomas. The largest leiomyoma in the posterior wall measured approximately 3.5 × 4.0 × 2.7 cm (Table 1). On September 3, 2019, the ultrasound results (Fig. 1b) confirmed an early intrauterine pregnancy. Multiple medium-to-low echogenicity lesions were observed in the myometrium, including a larger one in the posterior wall measuring approximately 5.5 × 3.5 cm. A cesarean section was performed on April 1, 2020 (36 + 4 weeks of gestation) due to premature rupture of membranes and a history of previous cesarean section. Intraoperatively, multiple leiomyoma-like masses were found in the posterior wall and bottom of the uterus, protruding into the serosal layer and not clearly into the mucosal layer. The most prominent lesion had a diameter of approximately 8.0 cm. After consulting with the patient, uterine myomectomy was withheld. One month after delivery (April 30, 2020), an ultrasound examination (Fig. 1c) showed multiple heterogeneous hypoechoic masses in the uterine region, with the largest one being 8.6 × 7.7 × 7.3 cm in the posterior wall, exhibiting capsular blood flow signals. Over two months after delivery, a follow-up ultrasound examination (Fig. 1d) revealed a hypoechoic mass of approximately 8.6 × 3.6 cm in the uterine cavity, displaying lacking blood flow signals. Myometrial echogenicity was homogeneous. No specific treatment was provided immediately, however, the patient reported lower abdominal distension and increased vaginal discharge. The leucorrhea test suggested vaginitis, and she was prescribed oral cefuroxime for 7 days. Over three months after delivery (July 24, 2020), a follow-up ultrasound examination showed a hypoechoic mass of approximately 6.5 × 3.4 cm in the uterine cavity, with visible blood flow signals and a resistance index (RI) of 0.44 (Table 1). The patient did not report significant abdominal pain, vaginal bleeding, or discharge during regular follow-up visits. The patient experienced a slightly increased menstrual flow as compared to before, without symptoms such as dizziness or weakness. Surgical treatment was recommended, but the patient declined. Annual follow-up ultrasound examinations (Fig. 1e, f and g) after delivery suggested a gradual reduction in the size of uterine leiomyomas. In the third postpartum year (May 8, 2023), the ultrasound examination (Fig. 1h) revealed no noticeable leiomyoma-like echoes in the posterior wall of the uterus (Table 1). During the whole treatment,the treatment principle is symptomatic management and regular follow-up under the condition of no severe complications, with surgical interventions pursued when required.