After the transvaginal ultrasound and basal assessment of the ovaries, on day 2 to day 3 of the menstrual cycle, luteal estradiol priming was stopped, and FPS was started with fixed dose of rec-FSH 300?IU/day plus LH 75?IU/day for 4?days. centers. To date, 310 poor prognosis patients completed a DuoStim protocol and underwent IVF with blastocyst-stage preimplantation-genetic-testing. LPS resulted into a higher mean number of oocytes collected than FPS; however, their competence (i.e., fertilization, blastocyst, euploidy rates, and clinical outcomes after euploid single-embryo-transfer) was comparable. Importantly, the rate of patients obtaining at least one euploid blastocyst increased from L-371,257 42.3% (production of follicles. Therefore, increasing the dose of gonadotrophins administered or even adopting more powerful drugs will never compensate a reduced ovarian reserve. In this scenario, a novel COS strategy has been proposed: double stimulation in the same ovarian cycle (DuoStim). Such protocol particularly suits poor prognosis and oncological patients, who require maximizing the exploitation of their ovarian reserve in a limited time (34C36). DuoStim, by combining conventional follicular phase stimulation (FPS) with luteal phase stimulation (LPS), can be considered a valuable option in patients with reduced ovarian reserve and/or advanced maternal age to maximize the number of oocytes retrieved in a single ovarian cycle, and for patients who did not collect oocytes or did not produce competent embryos after conventional FPS (37). The very first experience with double stimulation has been reported by Kuang and colleagues (36) who showed that COS conducted in both the FPS and L-371,257 LPS of the same ovarian cycle results in SHFM6 the collection of oocytes with similar developmental competence (36). The drugs used for COS in the Shanghai protocol, as it was called in the paper, were clomiphene citrate 25?mg/day, letrozole 2.5?mg/day, and mild dose of human menopausal gonadotrophin 150C225?IU/day. Moreover, the final oocytes maturation was induced with triptorelin followed by ibuprofen 0.6?g the day of trigger and the day after, in both FPS and LPS. In 2016, we published our proof-of-concept study where a DuoStim protocol was adopted together with a pre-implantation genetic testing (PGT-A) program in poor prognosis patients (34). The most important outcome outlined by this study was that the application of DuoStim in this thorny patient population increased the chance of obtaining at least one euploid blastocyst in a single ovarian cycle from 40 to 70%. Contrary to the Shanghai protocol, the DuoStim protocol consists in a co-treatment with maximal dose of FSH plus LH and GnRh antagonist to prevent ovulation in both FPS and LPS. The rationale of administrating FSH 300?IU/day plus LH 75?IU/day in an antagonist protocol, instead of adopting a mild stimulation, is to limit the risk for cycle cancelation and possibly decrease time-to-pregnancy by maximizing the number of oocytes collected per stimulation. To this regard, mild stimulation has been associated with a reduced number of oocytes retrievable per COS cycle (38). Therefore, even if no randomized controlled trial (RCT) has been performed to compare mild versus conventional COS in a DuoStim protocol, it is reasonable to hypothesize that while the cost of the former COS approach might involve lower expense than the latter (39), effectiveness is questionable. This is especially true if we account cumulative live birth rate per started cycle as the measure of success in IVF (40, 41). The patient drop-out is then another very important issue in the treatment of poor prognosis patients. It has been reported largely variable (20C60%) among couples undergoing IVF worldwide (42C44). Still, a generally valid information cannot be produced due to heterogeneity in terms of cost, reimbursement policies, accessibility to IVF, indication for PGT-A, etc., among the different countries (45, 46). Importantly, the most significant drop-out rate involves the second attempt after a first failed IVF cycle. Furthermore, when a second attempt is performed, ~10?months often pass from the former retrieval, while the time is crucial especially for poor prognosis individuals (47). These instances might be rescued the application of a DuoStim approach, which would at least allow to conduct two retrievals in one L-371,257 ovarian cycle. A future RCT comparing double FPS versus DuoStim and entailing also the drop-out rate among the outcomes under investigation might provide an answer to this issue. Indications to Duostim Since October 2015, DuoStim has been proposed at our four centers, after considerable counseling, to.