In a traditional stimulated IVF/ICSI cycle, follicle stimulation hormone (FSH) is administered in the first 10-14 days of the cycle to recruit and grow follicles. This is called the follicular phase. The patient then has a trigger injection followed by egg collection. After egg collection, the patient either has progesterone supplements to prepare the lining for an embryo transfer or the embryos are frozen for embryo testing; this is considered the luteal phase. If the embryo transfer is unsuccessful, or the patient is having PGT and freezing their embryos, they are usually required to wait 4-6 weeks before commencing their next treatment cycle.
What is dual stimulation?
Dual stimulation involves stimulating follicle growth in the follicular phase (as with conventional IVF/ICSI) and then a second time in the luteal phase. In the initial cycle, the process is the same as it is for conventional IVF/ICSI, and viable embryos are frozen. Three days after the initial egg collection, the patient will recommence FSH to essentially complete another cycle. Additional medications may be prescribed during the second stimulation phase. Once the FSH has resulted in adequate growth of follicles in the luteal phase cycle, the patient will again have another trigger injection and egg collection. The doctor may or may not recommend a fresh embryo transfer in the second cycle.
What is the theory behind dual stimulation?
Dual stimulation is based on the theory that follicles develop in waves throughout the menstrual cycle, rather than in synchrony at the beginning of the cycle. The purpose of re-stimulating the ovaries after egg collection is to recruit follicles that may have been too immature in their development to collect in the follicular phase; essentially allowing for more eggs to be collected within one menstrual cycle, rather than having to wait for subsequent cycles.
Several small studies suggest there is an increased number of eggs collected and number of good quality embryos frozen in the luteal stimulation cycle compared with the follicular phase cycle. Dual stimulation is indicated for people who require cryopreservation urgently (eg. people undergoing chemotherapy) and for people who have previously responded poorly to ovarian stimulation.
As the studies that have been conducted are small, more research is required to conclusively determine whether these findings translate to increased number of live births.
Polat M, Mumusoglu S, Yarali Ozbek I, Bozdag G and Yarali H. Double or dual stimulation in poor ovarian responders: where do we stand? Ther Adv Reprod Health. 2021, Vol. 15: 1–13 DOI: 10.1177/26334941211024172
Luo Y , Sun L, Dong M, Zhang X, Huang L, Zhu X, Nong Y and Liu F. The best execution of the DuoStim strategy (double stimulation in the follicular and luteal phase of the same ovarian cycle) in patients who are poor ovarian responders. Luo et al. Reproductive Biology and Endocrinology (2020);18:102. https://doi.org/10.1186/s12958-020-00655-3