The presence of an ovarian cyst is traditionally considered to be an indication for operative intervention for fear of ovarian cancer and acute complications of ovarian cysts, such as torsion, rupture and obstruction of labour. Two studies described the prevalence of ovarian cysts in pregnancy before the routine use of ultrasound, when the diagnosis was based on clinical examination of women with symptoms suggestive of an adnexal mass. The vast majority of adnexal cystic masses detected in early pregnancy are functional cysts, such as corpus luteum cysts or follicular cysts. Dermoid cysts or mature cystic teratomas are the most common complex ovarian masses encountered in pregnancy, making up 24-40% of all ovarian tumours. Fimbrial cysts are usually seen on ultrasound examination as thin-walled, anechoic, unilocular adnexal masses. Ultrasound-guided cyst aspiration offers a less invasive alternative to the traditional techniques employed for surgical management of ovarian cysts in pregnancy.