“…Several clinical cases of regressing tumors due to decidualization, infection, and rupture of ovarian endometriosis lesions during a pregnancy have been previously reported (16)(17)(18)(19)(20)(21)(22)(23); however, the frequency of those incidences was far from clear. In our current study, among the 25 ovarian endometriotic cysts, decidualization, abscess, and rupture of the ovarian endometriosis were for the first time demonstrated to occur in 12%, 4%, and 4% of the cases, respectively.…”