Prevalence:

• 1 in 2,500 births.
• Most common intra-abdominal cyst in female fetuses.

Ultrasound diagnosis:

• Unilateral, unilocular cyst, sometimes containing a ‘daughter cyst’, in the abdomen of a female fetus >26 weeks’ gestation.
• If the cyst undergoes torsion (40% of cases) or hemorrhage the appearance is complex or solid. Rupture can result in ascites.
• Fetal ovarian cysts are sensitive to placental hormones and are more common in diabetic or rhesus isoimmunised mothers as a result of placental hyperplasia.
• Large ovarian cysts (>6 cm in diamater) can cause polyhydramnios due to compression of the bowel.

Associated abnormalities:

• Most cases are sporadic and there is no association with chromosomal abnormalities.
• A few cases are associated with genetic syndromes. The most common is McKusick - Kaufman syndrome (automosomal recessive; hydrometrocolpos, polydactyly, heart defects).
• Other defects, mainly genitourinary (renal agenesis, polycystic kidneys) and gastrointestinal (esophageal atresia, duodenal atresia and imperforate anus), are often found.

Investigations:

• Detailed ultrasound examination.

Follow up:

• Ultrasound scans every 4 weeks to monitor the evolution of the cyst. If the cyst is >6 cm ultrasound guided aspiration should be considered.

Delivery:

• Place: hospital with neonatal intensive care and facilities for pediatric surgery
• Time: 38 weeks.
• Method: induction of labor aiming for vaginal delivery.

Prognosis:

• The majority of cysts are benign and resolve spontaneously in the neonatal period. Surgery may be necessary if there is torsion.

Recurrence:

• Isolated: no increased risk of recurrence.