How MRI imaging for an ovarian cyst led to diagnosis of short cervix

Background: Magnetic resonance imaging (MRI) during pregnancy is a growing diagnostic modality for a variety of different indications including fetal anomalies and maternal masses. A literature search did not find any case reports diagnosing a short cervix on MRI before 20 weeks gestation. Case presentation: A 34-year-old female underwent magnetic resonance imaging for further evaluation of a known ovarian cyst which demonstrated a multiseptated cystic mass measuring 15.5 × 9.9 × 18.5 cm in the right adnexa at 19 weeks gestation. An incidental finding on MRI of “bulging of membranes into the cervical canal to the level of the external os” was noted. The patient had 3 prior full-term cesarean deliveries with no history of short cervix. Ultrasound confirmed dilated cervix with no measurable cervix. The patient underwent a rescue cerclage. Conclusion: This case describes an unmeasurable cervix diagnosed incidentally during an MRI to characterize a large adnexal mass. In pregnancy, MRI can be a useful imaging modality to evaluate fetal anatomy, placental position and implantation, and abdominal and pelvic structures. In this case, evaluation of the uterus and cervix during imaging for an adnexal mass allowed for detection of an unmeasurable cervix and intervention with a rescue cerclage.