Fig. 1

Framework of DuoStim protocol. Each square represents a day. Violet squares identify the days before the beginning of the first ovarian stimulation (OS), when pre-treatment strategies might be adopted. Purple squares represent the days of first and second OS. Gray squares represent the days when no treatment is applied; if their contour is purple, they identify the possibility of starting the second OS soon after the first retrieval, as for the Shanghai protocol. Dark pink squares represent the days of oocyte pick-up (OPU). Light blue arrows identify ovulation trigger administration. Red brackets identify the timeframe when (possible) menstruation might occur. Orange brackets identify the timeframe of LH suppression regimen administration. The ovarian cycle is framed within a dotted green larger square. All possible pre-treatment, OS, LH suppression, and trigger options are listed in the figure. In the lower right corner, all possible lab strategies are shown: fresh oocytes insemination after both OPUs or oocyte cryopreservation after the first OPU, then warmed and inseminated along with the fresh oocytes obtained from the second OPU (dotted dark blue arrow) plus cleavage-stage embryo cryopreservation or blastocyst culture and blastocyst cryopreservation with/without trophectoderm (TE) biopsy for pre-implantation genetic testing. The squares mirror the same squares in the DuoStim protocol framework. The white numbers within each square are the days after OPU. GnRH-ant, GnRH antagonist; OCP, oral contraceptive pill; HMG, human menopausal gonadotropin; CC, clomiphene citrate; LE, letrozole; PPOS, progestin-primed ovarian stimulation; NSAID, non-steroidal anti-inflammatory drug