What is the best course of treatment for a 19-week pregnant patient with a history of endometriosis and a 4.8x4 cm ovarian endometrioma (chocolate cyst)?

Management of 4.8x4 cm Ovarian Endometrioma at 19 Weeks Gestation

Conservative management with close surveillance is the recommended approach for this patient, with surgery reserved only for acute complications such as rupture, torsion, or uncontrolled pain. 1

Rationale for Conservative Management

Natural History During Pregnancy

• Up to 70% of adnexal lesions identified during pregnancy resolve spontaneously, particularly functional cysts 1
• Endometriomas undergo decidualization during pregnancy due to high progesterone levels, causing morphological changes and potential atrophy of the endometriotic tissue 2
• The hormonal environment of pregnancy fundamentally suppresses endometriotic activity, providing therapeutic benefit 2

Surgical Risks at 19 Weeks

• Pregnant patients undergoing pelvic surgery face increased risks of fetal loss (1% for elective surgery, 5% for emergent), preterm birth (4% elective vs 12% emergent), and low birthweight compared to the general population 1
• While historically 16-20 weeks was considered optimal timing for non-emergent surgery, recent evidence shows no significant association between trimester of operation and adverse outcomes 1
• The magnitude of surgical risks must be weighed against the typically benign behavior of endometriomas during pregnancy 1

Specific Management Algorithm

Immediate Assessment

• Confirm diagnosis with combined transabdominal and transvaginal ultrasound to characterize the mass and exclude malignancy 1
• Critical caveat: Endometriomas can develop rounded vascularized papillary projections during pregnancy that mimic malignancy on imaging—this represents decidualization, not disease progression 1, 2
• Assess for acute complications: torsion (sudden severe pain, absent Doppler flow), rupture (peritoneal signs, free fluid), or hemorrhage 1

Conservative Management Protocol

• Serial ultrasound monitoring every 4-6 weeks to assess cyst size and characteristics 1
• Pain management with acetaminophen as first-line; avoid NSAIDs after first trimester 1
• Patient education about warning signs requiring immediate evaluation: sudden severe abdominal pain, fever, or signs of preterm labor 1

Indications for Surgical Intervention

Surgery should be performed only if:

• Acute torsion occurs (requires emergent laparoscopy or laparotomy with ovarian detorsion ± cystectomy) 1
• Cyst rupture with hemodynamic instability or peritonitis develops 1
• Intractable pain unresponsive to conservative measures that significantly impacts maternal well-being 1
• Rapid enlargement or development of concerning features suggesting malignancy (extremely rare: 0.8-6.8% of persistent masses) 1

Surgical Approach If Required

• Laparoscopy is feasible and preferred over laparotomy when technically possible, offering decreased blood loss, shorter operative time, reduced hospital stay, and significantly lower risk of adverse fetal outcomes (0.4% vs 1.8% composite adverse outcomes) 1
• Laparoscopy remains safe even in the second trimester, though visualization may be more challenging 1
• Ovarian cystectomy is preferred over ablation or drainage for definitive pathologic diagnosis and lower recurrence rates 3
• Avoid staging lymphadenectomy—this is not indicated for benign disease 1

Important Clinical Caveats

Diagnostic Pitfalls

• In one study of 53 suspected endometriomas on ultrasound during pregnancy, only 4 of 10 surgically excised lesions were actually endometriomas; others included mucinous cystadenomas 1
• Decidualization can cause endometriomas to lose their typical "ground glass" ultrasound appearance, making diagnosis challenging 1

Postpartum Considerations

• Definitive surgical management (if needed) should be deferred until at least 6-12 weeks postpartum when pregnancy-related changes have resolved 2
• Breastfeeding may extend symptom relief through continued anovulation 2
• Pregnancy provides long-term therapeutic benefit with reduced risk of endometriosis recurrence 2

What NOT to Do

• Do not perform elective cystectomy at 19 weeks simply because the cyst is present—the risks outweigh benefits in asymptomatic or minimally symptomatic patients 1
• Do not assume papillary projections or increased vascularity indicate malignancy—these features are expected with decidualization 1, 2
• Do not delay emergent surgery if acute complications develop—maternal safety takes priority 1