Missed deep ovarian pregnancy behind a ruptured corpus luteum: the value of postoperative β-hCG and methotrexate

Abstract Background Ovarian pregnancy accounts for only 0.5-3% of ectopic pregnancies. Its coexistence with a ruptured corpus luteum is exceptionally rare and creates a diagnostic challenge that can lead to incomplete treatment and persistent trophoblastic disease. Case presentation A 41-year-old G4P2 woman with a history of two cesarean sections presented with amenorrhea, abdominal pain, and vaginal bleeding. Serial β-hCG levels showed a fluctuating but overall rising trend (439 → 104 → 450 → 781mIU/mL). Diagnostic laparoscopy revealed a 2 cm superficially located, actively bleeding lesion on the right ovary, which was resected and pathologically confirmed as a ruptured corpus luteum (no trophoblastic tissue). Unexpectedly, postoperative β-hCG continued to rise (860 → 894mIU/mL). Repeat transvaginal ultrasound identified a 10 × 12 × 10 mm deep intra-ovarian lesion with peripheral vascularity, spatially distinct from the surgical site. Based on the persistent β-hCG rise, absence of intrauterine or tubal pregnancy, Doppler findings, and subsequent response to MTX, a clinically diagnosed deep ovarian pregnancy was considered. The patient was successfully treated with a two-dose methotrexate (MTX) regimen, achieving β-hCG normalization (< 5mIU/mL) within 3 weeks without adverse effects. Conclusion This rare dual pathology illustrates how a symptomatic ruptured corpus luteum can act as a “decoy,” masking a deep ovarian pregnancy. The case underscores that postoperative β-hCG surveillance is indispensable for verifying complete resection, and that MTX can be a safe, effective, and fertility-preserving salvage option for residual deep trophoblastic tissue.