What is the likely diagnosis for a 40-year-old female with severe abdominal pain, four weeks after embryonic (embryo) transfer for primary infertility?

Diagnosis: Ectopic Pregnancy is Most Likely

In a 40-year-old woman presenting with severe abdominal pain four weeks after embryo transfer, ectopic pregnancy is the most probable diagnosis and must be ruled out immediately with transvaginal ultrasound and β-hCG measurement. 1, 2

Why Ectopic Pregnancy is the Primary Concern

IVF Dramatically Increases Ectopic Risk

• Ectopic pregnancy occurs in approximately 1.5-2.1% of IVF patients, which is substantially higher than the general population 3
• The 4-week timeframe post-embryo transfer corresponds precisely to when ectopic pregnancies typically present with symptoms (around 6-8 weeks gestational age) 4, 5
• Fresh embryo transfer and transfer of multiple embryos (common in IVF) are associated with higher ectopic rates 3

Abdominal Ectopic is a Documented IVF Complication

• Abdominal ectopic pregnancy, though rare, has been specifically documented after IVF-embryo transfer, even in patients with bilateral salpingectomy 6, 7, 3
• This can occur through direct peritoneal implantation during embryo transfer 7
• Severe abdominal pain is the hallmark presentation 6, 7

Why Ovarian Torsion is Less Likely (But Still Possible)

Timing Makes Torsion Less Probable

• Ovarian torsion after IVF typically occurs earlier—during or immediately after ovarian hyperstimulation, not 4 weeks post-transfer 4
• The two documented cases of post-IVF torsion presented at 6 and 8 weeks gestation, but the acute event likely occurred closer to the stimulation phase 4
• By 4 weeks post-transfer, ovarian hyperstimulation has usually resolved, reducing torsion risk

Clinical Presentation Differs

• Torsion typically presents with sudden-onset, intermittent pain (as the ovary twists and untwists), whereas ectopic rupture causes persistent, severe pain 4
• Torsion would show an enlarged ovary with decreased/absent Doppler flow on ultrasound 1, 2

Immediate Diagnostic Approach

First-Line Testing

• Obtain serum β-hCG immediately—this is mandatory in all reproductive-age women with abdominal pain 2
• Perform transvaginal ultrasound with transabdominal views—this is the single best diagnostic modality for ectopic pregnancy with 99% sensitivity and 84% specificity 1

Key Ultrasound Findings to Assess

• Look for absence of intrauterine pregnancy with β-hCG >3,000 mIU/mL—this strongly suggests ectopic pregnancy 1
• An adnexal mass without intrauterine pregnancy has a positive likelihood ratio of 111 for ectopic 1
• Assess for free fluid in the pelvis and Morrison's pouch, which suggests rupture 1
• Evaluate both ovaries for size, masses, and Doppler flow to rule out torsion 1, 2

Critical Management Points

Do Not Delay

• If ectopic pregnancy is confirmed or highly suspected, immediate obstetric consultation is required for methotrexate versus surgical management 2
• Hemodynamic instability or significant free fluid indicates rupture requiring emergency surgery 1

Consider Heterotopic Pregnancy

• In IVF patients, heterotopic pregnancy (simultaneous intrauterine and ectopic) occurs in up to 46% of abdominal ectopic cases 3
• The presence of an intrauterine pregnancy does NOT exclude ectopic pregnancy in this population 3

Bilateral or Asynchronous Ectopic is Possible

• Bilateral tubal pregnancy with asynchronous development has been documented after transfer of ≥2 embryos 5
• If β-hCG fails to decline appropriately after treating one ectopic, consider a second ectopic location 5

Common Pitfalls to Avoid

• Do not assume ovarian torsion based solely on IVF history—the timing (4 weeks post-transfer) makes ectopic far more likely 4, 3
• Do not rely on β-hCG discriminatory zone of 1,000-2,000 mIU/mL—current guidelines recommend 3,000 mIU/mL as the threshold 1
• Do not use CT as first-line imaging—ultrasound is superior for gynecological causes and avoids radiation exposure 2, 8
• Do not dismiss the possibility of abdominal ectopic even if the patient has had bilateral salpingectomy 6, 3