Most Common Adnexal Mass in Early Pregnancy and Management
The most common incidentally identified adnexal mass in early pregnancy is a simple cyst <5 cm (representing approximately 75% of all detected masses), but among masses that ultimately require surgical management, dermoid cysts are most common at 32%. 1
Understanding the Distinction
There is an important clinical distinction to clarify:
- Physiologic corpus luteum cysts are indeed present in every early pregnancy as a normal finding, but they typically measure <3 cm and are not classified as pathologic "masses" requiring clinical attention 2
- Clinically significant adnexal masses detected on ultrasound are found in 2-20 per 1,000 pregnancies, approximately 2-20 times more frequently than in age-matched non-pregnant women 1, 2
Distribution of Masses Requiring Surgical Management
Among adnexal masses that persist and require surgical intervention during pregnancy 1, 2:
| Mass Type | Incidence |
|---|---|
| Dermoid cysts (mature cystic teratoma) | 32% (18-50%) |
| Serous + mucinous cystadenomas | 19% combined |
| Endometriomas | 15% (0-24%) |
| Functional cysts | 12% (3-41%) |
| Hyperreactio luteinalis | 9% (0-14%) |
| Malignancy | 2% (0-6%) |
Management Algorithm
For Simple Cysts <5 cm with Benign Features
- Expectant management with serial ultrasound surveillance is appropriate 1, 2
- 68-72% of complex masses measuring 2.5-5 cm spontaneously resolve by 6 weeks postpartum 1, 2
- No intervention is needed unless symptoms develop (pain, torsion) 1, 2
For Masses ≥5 cm Persisting Beyond First Trimester
- Surgical intervention should be considered, preferably in the second trimester when spontaneous resolution is unlikely and uterine size still permits adequate visualization 1, 2
- Second trimester timing balances allowing time for spontaneous resolution while optimizing surgical access 1
For Masses ≥10 cm
- Surgical removal is strongly recommended because larger lesions carry markedly higher torsion risk (mean size of torsed masses ≈10 cm) 2
- Overall torsion risk in pregnancy is 3-12%, with highest incidence in large masses 2
- These masses are unlikely to resolve spontaneously 2
Diagnostic Approach
- Transvaginal ultrasound is the first-line imaging modality throughout pregnancy—highly accurate, safe, inexpensive, and widely available 2, 3
- Reported ultrasound diagnostic accuracies: 95% for dermoid tumors, 80% for endometriomas, 71% for simple cysts 2
- Gadolinium-enhanced MRI is contraindicated in pregnancy; non-contrast MRI may be used if ultrasound is nondiagnostic, though rarely needed 2
Red-Flag Features Suggesting Malignancy
Ultrasound findings that warrant heightened concern 2:
- Thick or irregular septations
- Mural nodules or papillary projections
- Solid components
- Maximum diameter >5 cm
When malignancy is suspected, laparotomy (not laparoscopy) is advised to allow appropriate oncologic staging 2
Surgical Technique When Indicated
- Laparoscopic cystectomy is strongly preferred over laparotomy for benign-appearing masses, offering 2:
- Shorter hospital stay and less postoperative pain
- Lower fetal loss rate (1% vs 5%)
- Lower preterm birth rate (4% vs 12%)
- Reduced blood loss
Technical Modifications for Pregnancy
- Left lateral decubitus positioning after first trimester 1, 2
- Insufflation pressure ≤12-15 mm Hg 1, 2
- Port placement adjusted for fundal height 1, 2
- Continuous intraoperative capnography 1, 2
- Pre- and postoperative fetal heart rate monitoring 1, 2
Critical Pitfalls to Avoid
- Do not delay necessary surgery based solely on gestational age—when intervention is indicated, it should proceed with appropriate obstetrical and anesthetic support 1
- Do not assume all functional cysts will resolve—masses ≥5 cm persisting beyond first trimester warrant surgical consideration 1, 2
- Recognize that endometriomas may undergo decidualization in pregnancy, mimicking borderline or invasive malignancy on imaging 3
- If a ≥10 cm adnexal mass is discovered incidentally during cesarean delivery, remove it during the same operation to avoid second surgery and eliminate postpartum torsion risk 2
Pregnancy-Specific Masses
- Hyperreactio luteinalis presents as bilateral ovarian enlargement with multiple thin-walled cysts, typically in third trimester, due to hCG hyperstimulation 1
- This condition regresses spontaneously after delivery and does not require intervention 1, 2