Evidence-Based Resource

Natural History Ovarian Cysts?

Evidence Level IV

Ovarian cysts are the most commonly diagnosed abdominal abnormality in prenatal females. Despite its frequent presentation, there remains a paucity of knowledge surrounding the natural history of these cysts. Controversy remains for optimal management and indications for surgical management and drainage are poorly understood. Bascietto and colleagues performed a systematic review and meta-analysis to investigate the outcomes of ovarian cysts prenatally diagnosed by ultrasound. A total of 34 studies published from 2000 to 2016 were identified, with a total of 954 fetuses included in the analysis. 33 of the studies were retrospective reviews, and 1 was a prospective cohort analysis. Results for the overall population and several subgroups were pooled and analyzed:

Resolution of the cyst:
- Overall: PP 53.8% (95% CI: 46.0-61.5%) of prenatally diagnosed cysts in fetuses were resolved during pregnancy or after birth;
- PP 69.4% (95% CI: 59.0-79.0%) of simple cysts were resolved;
- Complex cysts were less likely to resolve than simple cysts: OR 0.15 (95% CI: 0.10-0.23); and
- Cysts ≥ 40 mm were less likely to resolve than cysts < 40 mm: OR 0.03 (95% CI: 0.01-0.06)

Change of ultrasound pattern
- PP 23.6% (95% CI: 14.4-34.4%) of simple cysts changed to complex cysts during pregnancy or at birth;
- Cysts measuring ≥ 40 mm were more likely to change ultrasound pattern during pregnancy than cysts measuring < 40 mm: OR 3.16 (95% CI: 1.02-9.7); and
o Of these, PP 57.7% (95% CI: 42.9-71.8%) resulted in ovarian loss due to surgical removal or ovarian amputation

Ovarian torsion:
- Incidence: 21.8% (95% CI: 15.2-29.2%) for cysts overall, 6.0% (95% CI: 3.6-8.9%) for simple cysts, and 44.9% (96% CI: 31.7-58.54%) for complex cysts;
- Ovarian torsion for cysts ≥ 40 mm was more likely than cysts < 40 mm: OR 30.8 (95% CI: 8.6-110.0); and
- More likely for complex cysts than simple cysts: OR 59.1 (95% CI: 24.7-141.0)

Intracystic hemorrhage:
- Incidence: 6.8% (95% CI: 3.7-10.8%) of cyst cases;
- More likely for complex cysts than simple cysts: OR 28.6 (95% CI: 4.9-∞);
- More likely for cysts ≥ 40 mm than cysts < 40 mm: OR 31.7 (95% CI: 3.7-270.0); and
- Greater likelihood for simple cysts ≥ 40 mm than simple cysts < 40 mm: OR 63.4 (95% CI: 10.7-∞)

Surgery
- Surgical intervention: Overall 39.5% (95% CI: 30.1-49.3%) of fetuses with a prenatal diagnosis of
ovarian cysts had surgery, 24.6% (95% CI: 14.2–36.9%) for simple cysts, and 64.8% (95% CI:
52.2–76.3%) for complex cysts;
- Patients with cysts ≥ 40 mm were more likely to have surgery than patients with cysts < 40 mm:
OR 64.4 (95% CI: 23.6-175.0);
- Patients with complex cysts were more likely to have surgery than patients with simple cysts: OR
14.6 (95% CI: 8.5-24.8); and
- Ovarian loss due to oophorectomy or salpingo-oophorectomy occurred in 25.1% (95% CI: 17.2-
34.0%) of surgical cases

Complex cysts and cysts ≥ 40 mm were associated with an increased odds of ovarian loss: 35.1 (95% CI:
17.0-72.7) and 58.9 (95% CI: 19.2-181.0), respectively.
Following intrauterine aspiration:
- No reoccurrence either during pregnancy or after birth PP 48.9% (95% CI: 25.0–74.0%);
- Reoccurrence occurred in 37.9% (95% CI: 14.8–64.3%) of cases;
- Increase in cyst size occurred in 6.9% (95%CI: 2.0–14.5%);
- Change of ultrasound pattern from simple to complex cyst: 7.9% (95% CI: 2.6–15.8%);
- Ovarian torsion: 10.8% (95% CI: 4.4–19.7%);
- Intracystic hemorrhage: 12.8% (95% CI: 3.8–26.0%);
- Rate of preterm delivery: 5.1% (95% CI: 0.7–13.0%); and
- Rate of miscarriage: 21.8% (95% CI: 0.9–40.0%)

Misdiagnosis:
- Rate: 7.5% (95% CI: 4.4–11.4%)
o Misdiagnosis occurred for gastrointestinal anomalies: 54.1% (95% CI: 28.1–78.9%);
o Urogenital anomalies:14.9% (95% CI: 6.6–25.6%); and
o Renal anomalies:10.3% (95% CI: 4.0–19.1%)

Histopathological assessment:
- Available for 385 cases
o Cysts were either follicular or theca lutein: 93.0% (95% CI, 87.7–96.8%);
o Cystadenoma: 2.1% (95% CI, 0.9–3.7%); and
o Teratoma: 1.5% (95% CI, 0.5–2.9%)

PP = Pooled Proportion; OR = Odds Ratio; CI = Confidence Interval

Conclusions: Over half of all prenatally diagnosed ovarian cysts regress without intervention. Size and
complexity of cysts are determinants of outcomes. Larger cysts and complex cysts are associated with a
higher risk of ovarian torsion, intracystic hemorrhage, and may lead to oophorectomy.

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