Pregnancy And Neonatal Outcomes Of hMG Stimulation With Or Without Letrozole In Endometrial Preparation For Frozen–Thawed Embryo Transfer In Ovulatory Women: A Large Retrospective Cohort Study

Abstract

Objective

Frozen–thawed embryo transfer enables surplus embryos derived from IVF or IVF-ICSI treatment to be stored and transferred in subsequent cycles into a more “physiologic environment”. This study aimed to investigate the clinical effect of letrozole use or hMG stimulation on pregnancy and neonatal outcomes in ovulatory patients undergoing FET.

Methods

This study includes a total of 5901 FET cycles with letrozole use (n = 1569), HMG (n =1827) or letrozole + HMG (n = 2505). In the letrozole group, 2.5 mg of letrozole was administered on menstrual cycle day 3 to 5 for 3 days for patients, and then follicle growth was monitored beginning on day 10. If the follicular diameter was ≥14 mm on the 10th day, no other ovarian stimulation drugs were needed. If the follicular diameter was <14 mm on the 10th day, 150 IU human menopausal gonadotropin (hMG) was added to stimulate follicle growth every two days (hMG + letrozole group). In hMG stimulation group, a total of 150 IU of hMG was injected every two days to stimulate development of follicles from cycle day 10 to 12.

Results

Compared with the patients undergoing hMG stimulation, the group receiving letrozole or letrozole+HMG stimulation exhibits significantly higher clinical pregnancy rates per transfer (hMG: 47.02% vs letrozole: 52.07% vs letrozole+HMG: 52.26%) and implantation rates (hMG: 31.76% vs letrozole: 34.36% vs letrozole+HMG: 34.24%). In addition, the letrozole group was associated with a statistically significantly lower incidence of miscarriage (hMG: 14.78% vs letrozole: 10.53% vs letrozole+HMG: 14.13%) and ectopic pregnancies (hMG: 1.83% vs letrozole: 0.97% vs letrozole+HMG: 1.58%) than the letrozole + HMG and HMG groups. Neonatal outcomes are similar among the three groups.

Conclusion

Our data demonstrate that the letrozole use may improve clinical pregnancy outcomes and decrease the risk of ectopic pregnancies and miscarriage in ovulatory patients who receive FET cycles.

Keywords:

• frozen–thawed embryo transfer
• Letrozole
• ovulation induction
• hMG
• clinical efficacy

Acknowledgements

We would like to appreciate Dr Qianqian Zhu‘s generous help with statistical analysis.

Abbreviations

FET, frozen–thawed embryo transfer; PCOS, polycystic ovary syndrome; ART, assisted reproductive technology; hMG, human menopausal gonadotropin.

Ethics Approval And Consent To Participate

This study was approved by the Ethics Committee (Institutional Review Board) of Shanghai Ninth People’s Hospital.

Availability Of Data And Material

The corresponding authors can be contacted regarding data requests.

Disclosure

The authors declare that they do not have any commercial or associative interest that represents a conflict of interest in connection with the published work.

Additional information

Funding

This research was supported by grants from National Natural Science Foundation of China (81801526, 81801527 and 31770989), Shanghai ninth hospital (JYLJ030).