Flexibility in starting ovarian stimulation at different phases of the menstrual cycle for treatment of infertile women with the use of in vitro fertilization or intracytoplasmic sperm injection

We discuss how flexibly started ovarian stimulation is feasible regardless of menstrual cycle phase in in vitro fertilization or intracytoplasmic sperm injection.

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Volume 106, Issue 2, Pages 334-341


Ningxin Qin, M.M., Qiuju Chen, Ph.D., Qingqing Hong, M.D., Renfei Cai, M.D., Hongyuan Gao, M.D., Yun Wang, M.D., Lihua Sun, M.D., Shaozhen Zhang, M.D., Haiyan Guo, M.D., Yonglun Fu, M.D., Ai Ai, M.D., Hui Tian, M.D., Qifeng Lyu, Ph.D., Salim Daya, MBChB, Yanping Kuang, M.D.



To investigate flexibility in starting controlled ovarian stimulation at any phase of the menstrual cycle in infertile women undergoing treatment with assisted reproduction.


Retrospective cohort study.


Academic tertiary-care medical center.


At total of 150 infertile patients undergoing in vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) treatment. Ninety of the women also underwent frozen embryo transfer (FET) procedures.


Depending on the phase of the menstrual cycle when ovarian stimulation was started, three groups of patients were identified, namely: conventional group (ovarian stimulation started in the early follicular phase), late follicular phase group, and luteal phase group. When dominant follicles were observed, final oocyte maturation was triggered with the use of GnRH agonist and hCG. In all three groups, viable embryos were cryopreserved for subsequent transfer.

Main Outcome Measure(s)

Primary outcome: number of mature oocytes retrieved. Secondary outcomes: fertilization rate, viable embryo rate per oocyte retrieved, cancellation rate, and clinical pregnancy outcomes from FET cycles.


There were no differences in the mean number of mature oocytes retrieved in the conventional group, late follicular phase group, and luteal phase group (5.7 ± 3.6, 5.2 ± 3.7, and 5.2 ± 3.9, respectively). Similarly, no significant differences were observed in the viable embryo rate per oocyte retrieved (37.9%, 38.5%, and 43.6%), clinical pregnancy rates (41.5%, 45.5%, and 38.9%), and implantation rates (30.7%, 30.2%, and 27.1%) in the three groups.


All three ovarian stimulation protocols were observed to be equally effective. These results demonstrate that ovarian stimulation can be commenced on any day of the menstrual cycle.

Clinical Trial Registration Number


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Fertility and Sterility

Editorial Office, American Society for Reproductive Medicine

Fertility and Sterility® is an international journal for obstetricians, gynecologists, reproductive endocrinologists, urologists, basic scientists and others who treat and investigate problems of infertility and human reproductive disorders.