Low-Oestrogen IVF Protocol Leading to Successful Pregnancy in Recurrent Microinvasive Seromucinous Borderline Ovarian Tumour

A 32-year-old woman with recurrent microinvasive seromucinous borderline ovarian tumour (SMBOT) and low ovarian reserve presented for fertility preservation prior to definitive surgery. After multidisciplinary evaluation, she underwent right adnexectomy and left ovarian cystectomy, with pathology confirming microinvasive SMBOT and no extraovarian spread. Controlled ovarian stimulation using a progestin-primed ovarian stimulation (PPOS) protocol with letrozole minimised oestrogen exposure was done and resulted in eight retrieved oocytes and four blastocysts. Following an initial failed frozen embryo transfer (FET), a second stimulation cycle produced two additional blastocysts. Hysteroscopy identified chronic endometritis, which was treated before a natural-cycle frozen transfer of a single 4AA blastocyst, resulting in an ongoing singleton intrauterine pregnancy. This case demonstrates that thoughtfully planned, low-oestrogen stimulation and coordinated oncologic surveillance may allow safe fertility preservation in selected patients with recurrent microinvasive SMBOT.