Review Question - QID 212534

A 36-year-old G4P1021 woman comes to the emergency room complaining of intense abdominal pain and vaginal bleeding. She is 9 weeks into her pregnancy and is very concerned as she experienced similar symptoms during her past pregnancy losses. Her pain is described as “stabbing, 10/10 pain that comes and goes.” When asked about her vaginal bleeding, she reports that “there were some clots initially, similar to my second day of menstruation.” She endorses joint pains that is worse in the morning, “allergic” rashes at her arms, and fatigue. She denies weight loss, chills, fever, nausea/vomiting, diarrhea, or constipation. Physical examination reveals an enlarged and irregularly shaped uterus with a partially open external os and a flesh-colored bulge. Her laboratory findings are shown below:

Serum:
Hemoglobin: 11.8 g/dL
Hematocrit: 35%
Leukocyte count:7,600 /mm^3 with normal differential
Platelet count: 200,000/mm^3
Bleeding time: 4 minutes (Normal: 2-7 minutes)
Prothrombin time: 13 seconds (Normal: 11-15 seconds)
Partial thromboplastin time (activated): 30 seconds (Normal: 25-40 seconds)

What is the most likely cause of this patient’s symptoms?