Background. Ovarian cysts are met in women of various ages, most commonly occurring during a woman's childbearing years, pregnant women not being an exception. Moreover, studies conclude that ovarian cancer is among top five types of cancers detected during pregnancy. The latest data show that the incidence of ovarian cysts in pregnancy varies from 0.15 to 5.7% malignancies ranging from 0.8 to 13%. Their evolution is frequently hard to predict, some cysts stop growing or disappear, while other may rupture, torsion or cause the obstruction of the delivery pathways. Only ovarian cysts at risk of complication are to be considered. These are mainly ovarian cysts, which, whatever their echogenic features, have a size ≥5 cm. Their prevalence is estimated between 0.5 and 2 per thousand of pregnancies. Case report. Patient X, 21 y.o., primigesta, pregnant 36-37 w. a., underwent a routine gynecological and ultrasonographic examination, during which she was firstly diagnosed with a giant 195x115 mm cyst in the projection of the right adnexa, supposedly originating from the ovary. Considering the gestational term and the lack of data for cyst complications, an expectative management was chosen and a re-evaluation was scheduled in two weeks. Consequently, the woman was admitted to the IMSP IM and C 3rd level hospital for further monitoring, investigations and establishing the optimal birth management. The next performed USG showed that the dimensions of the cyst have grown to 223x123 mm, it was mainly situated in the subhepatic space, it’s precise origin was hard to determine. It was decided to finish the pregnancy via caesarean section and invite a general surgeon to the intervention, in case other surgical manipulations would be needed. The tumoral markers were determined, with no deviations found: CA125 – 13,5 (N≤ 35); HE4 – 35 (N≤70); ROMA index – 3,4 (N 0 – 11,4%). At the term of 38-39 w.a. an elective caesarean section was performed. It was established that the cyst had an ovarian origin and was fully extracted. The abdominal cavity was drained. Total haemorage-800 ml. The woman and the newborn were discharged home on the 4th postoperatory day. The histological exam revealed an ovarian dymorphus sero-mucinous cystadenome, with a 2+ to 3+ mucin reaction, follicular cysts and lonely, distrofic primordial follicles. Conclusions. Though ovarian cysts are seldom met in pregnancy, their presence may have serious repercussions on the evolution of the pregnancy and on the fetus. This is why, even in the absence of symptoms, an USG supervision combined with other methods for diagnostic is necessary. The decision upon the optimal birth way should be taken individually in each case, the histological exam being crucial for establishing the final diagnosis.