How to manage a pregnancy with a small endometrioma on the left ovary?

Management of Small Endometrioma During Pregnancy

For a pregnant patient with a confirmed intrauterine pregnancy and a small endometrioma on the left ovary, expectant management with serial ultrasound monitoring is the recommended approach, as approximately 70% of endometriomas spontaneously resolve or decrease in size during pregnancy. 1

Initial Management Strategy

Adopt a conservative "wait-and-watch" approach for small endometriomas (<10 cm) during pregnancy. 2 The natural history of endometriomas during pregnancy is generally favorable:

• 68% of endometriomas decrease in size during pregnancy, with 40% disappearing completely by the postpartum period 2
• 27% remain unchanged in size 2
• Only 5% increase in size 2
• Small endometriomas (particularly those <6 cm with smooth walls) can be safely observed 3

Ultrasound Surveillance Protocol

Perform serial ultrasound examinations to monitor cyst characteristics and size changes throughout pregnancy. 1

Key ultrasound features to document at each visit:

• Cyst diameter and any changes >1 cm (considered significant) 2
• Internal echogenicity (ground-glass appearance is typical for endometriomas) 4
• Wall characteristics (smooth vs irregular, presence of papillary projections) 4
• Vascularity on color Doppler imaging 1
• Presence of septations or solid components 4

Follow the O-RADS US criteria for premenopausal patients: typical endometriomas <10 cm warrant optional follow-up at 8-12 weeks, then annual surveillance if not surgically removed. 1

Risk Factors Requiring Heightened Surveillance

Monitor closely for clinical features associated with increased risk of complications:

• Cyst diameter ≥6 cm 2
• Progressive increase in cyst size during pregnancy 2
• Adhesions to surrounding structures 2
• Development of new vascular components or changing morphology 1
• Compression from the enlarging uterus in late pregnancy 2

The overall rupture rate is low (2.8%), but these factors increase risk. 2

Indications for Surgical Intervention

Surgery during pregnancy is reserved for specific high-risk scenarios:

Absolute Indications:

• Acute symptoms of ovarian torsion 4, 3
• Suspicion of malignancy based on ultrasound features (solid components, papillary projections, irregular walls, increased vascularity) 3
• Cyst rupture with acute abdomen 2

Relative Indications:

• Large cysts (>10 cm) with progressive growth 3
• Persistent concerning ultrasound features despite observation 4

If surgery is necessary, laparoscopic cystectomy is the preferred approach during the second trimester (14-17 weeks gestation), as it is relatively safe with appropriate precautions. 3 However, necessary surgery should not be delayed based solely on gestational age. 1

Important Caveats and Pitfalls

Beware of diagnostic uncertainty: Only 40% of cysts presumed to be endometriomas on ultrasound during pregnancy are confirmed as such on pathology. 4 Other diagnoses include mucinous cystadenomas (common misdiagnosis), serous cystadenomas, and dermoid cysts. 4

Decidualization can mimic malignancy: Endometriomas may undergo decidualization during pregnancy, creating solid-appearing components that raise concern for malignancy on imaging. 3 This phenomenon lacks specific distinguishing clinical characteristics from true malignancy. 3

Do not assume all cysts will resolve: While most improve, 19% may ultimately require surgical treatment, and recurrence rates remain significant (documented in follow-up studies). 4, 3

Postpartum Management

Perform follow-up ultrasound 6-12 weeks postpartum to reassess any persistent endometriomas. 2, 4

• If the cyst has resolved or significantly decreased, continue routine gynecologic care 2
• If the cyst persists or has grown, refer to gynecology for consideration of surgical management 4
• Counsel patients about recurrence risk (up to 35% in some series) and the potential need for definitive surgical treatment after completion of childbearing 5

The risk of malignant transformation in endometriomas is higher in postmenopausal patients, but remains a consideration that should inform long-term management decisions. 1