Differential Diagnosis

• Single most likely diagnosis
  • Early pregnancy loss or failed pregnancy: This is the most likely diagnosis given the negative UPT on Oct 18 and the subsequent spotting/bleeding. The endometrial thickness of 14.5mm on Oct 20 could indicate a non-viable pregnancy or an early miscarriage.
• Other Likely diagnoses
  • Implantation bleeding: Although the spotting/bleeding occurred a bit late for typical implantation bleeding, it's still a possibility, especially if the embryo implanted later than expected.
  • Progesterone withdrawal bleeding: The progesterone pessary was stopped on Oct 16, and the spotting/bleeding started on Oct 21, which could be a withdrawal bleed.
  • Luteal phase defect: The endometrial thickness of 14.5mm might not be sufficient to support a pregnancy, indicating a luteal phase defect.
• Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
  • Ectopic pregnancy: Although the scan on Oct 20 did not show any abnormalities, an ectopic pregnancy can be life-threatening and should be ruled out, especially if the patient experiences severe abdominal pain or heavy bleeding.
  • Molar pregnancy: A molar pregnancy can cause abnormal uterine bleeding and should be considered, especially if the endometrial thickness is excessive.
• Rare diagnoses
  • Asherman's syndrome: This condition, characterized by intrauterine adhesions, can cause abnormal uterine bleeding and recurrent pregnancy loss. However, it's a rare condition and would require further evaluation.
  • Thyroid dysfunction: Thyroid problems can cause abnormal uterine bleeding and affect fertility. Although rare, it's essential to consider thyroid function, especially if other symptoms are present.