uk-drcog MCQ (SBA): Cervical Ectropion in Pregnancy

A 28-year-old woman at 26 weeks of gestation presents to the GP with vaginal bleeding. An ultrasound at 20 weeks reported a normally sited placenta. She describes a small amount of dark red blood mixed with mucus. She has no pain and her observations are normal. On speculum examination, the cervical os is closed with a small amount of blood at the os. What is the most likely cause?