A woman in early pregnancy with light vaginal bleeding, lower abdominal pain, cramping, and shoulder pain—what is the most likely diagnosis?

• A. Ovarian torsion
• B. Miscarriage
• C. Ectopic pregnancy
• D. Pelvic inflammatory disease

Answer: (C)

This pattern points to an ectopic pregnancy. When pregnancy occurs outside the uterus, it can cause vaginal bleeding and lower abdominal cramping in the early weeks, but the presence of shoulder pain is a telling sign. Shoulder pain arises because bleeding into the peritoneal cavity from a ruptured or bleeding ectopic irritates the diaphragmatic nerves, producing referred pain to the shoulder. That combination—early pregnancy with light vaginal bleeding, cramping, and referred shoulder pain—fits ectopic pregnancy much more than the other options.

Ovarian torsion typically presents as sudden, severe, one-sided pelvic pain with little to no pregnancy-related bleeding. Miscarriage can involve bleeding and cramps, but shoulder pain due to diaphragmatic irritation is not a typical feature unless there’s significant intra-abdominal bleeding from rupture, which makes the scenario less classic for miscarriage. Pelvic inflammatory disease usually presents with fever, abnormal vaginal discharge, and cervical motion tenderness rather than the specific early-pregnancy symptoms plus referred shoulder pain.

Because ectopic pregnancy can rupture and cause life-threatening hemorrhage, this presentation requires urgent evaluation with a pregnancy test and imaging to confirm location of the pregnancy.