Diagnosis of a Large Vaginal Cyst During Pregnancy.

In this report, we detail an unusual presentation of a large Müllerian cyst during pregnancy. A primigravida woman, 25 weeks and 6 days pregnant, arrived at the Obstetrics and Gynecology Emergency Department at Qatif Central Hospital, Saudi Arabia, complaining of something protruding from her vagina, accompanied by a yellowish vaginal discharge and mild back pain. After a series of initial examinations and tests, the patient was diagnosed with cervical incompetence and prolapsed fetal membranes, indicating a threat of preterm labour. However, after a lengthy hospital stay, multiple readmissions, and inconsistencies in the patient's history that contradicted the initial diagnosis, there was a rising suspicion about the nature of the vaginal mass. The patient was re-evaluated with a detailed examination and targeted pelvic ultrasound, which led to the diagnosis of a vaginal cyst. Cyst aspiration was performed before labour, but the patient was unable to deliver vaginally. Consequently, she underwent an emergency cesarean section, followed by an excision of the vaginal cyst. Histopathological analysis finally revealed that the cyst was a Müllerian cyst.