Dataset Information

Frozen Embryo Transfer in Mildly Stimulated Cycle With Letrozole Compared to Natural Cycle in Ovulatory Women: A Large Retrospective Study.

ABSTRACT:

Objective

To evaluate the clinical effect of mild stimulation with letrozole on pregnancy outcomes in ovulatory women undergoing frozen embryo transfer (FET) compared to natural cycle.

Design

Retrospective observational study.

Setting

Tertiary care academic medical center.

Population

A total of 6,874 infertile women with regular menstrual cycles (21-35 days) met the criteria for this study in the period from 2013 to 2020.

Methods

All patients who were prepared for and underwent FET were divided into two groups: a modified natural cycle (NC) group (n=3,958) and a letrozole cycle group (n=2,916).

Main outcome measures

The primary outcome of the study was clinical pregnancy rate. Secondary outcome measures were endometrial thickness, rates of implantation, positive HCG test, live birth, early miscarriage and ectopic pregnancy.

Results

The clinical pregnancy rate was not statistically different between the modified NC-FET group and the letrozole-FFT group before (crude OR 0.99, 95% CI 0.90-1.09, P=0.902>0.05) and after propensity score matching (PSM) (crude OR 1.01, 95% CI 0.91-1.12, P=0.870>0.05). After multivariable logistic regression analysis, the clinical pregnancy rate remained insignificant before (adjusted OR 1.00, 95% CI 0.91-1.10, P=0.979>0.05) and after matching (adjusted OR 1.00, 95% CI 0.89-1.11, P=0.936>0.05), respectively. Similarly, in the crude and adjusted analysis, the positive HCG test, implantation, live birth and early miscarriage rates were also comparable in the letrozole-FFT group and modified NC-FET group before and after matching. Furthermore, the endometrial thickness of letrozole-FFT group was similar to that of modified NC-FET group with adjusted analysis.

Conclusion

Our observation suggests that mild stimulation with letrozole could produce similar pregnancy outcomes in ovulatory patients who undergo FET when compared with a natural cycle.

SUBMITTER: Li D

PROVIDER: S-EPMC8493067 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Background: Nowadays, the choice of frozen embryo transfer (FET) regimens is mainly guided by personal convenience. Clinicians prefer the predictability and reliability of artificial cycle (AC) FET and have extended its usage to general in vitro fertilization population. More recent primary studies are beginning to challenge the comparability of AC-FET and suggest reduced clinical pregnancy rate and live birth rate (LBR) compared with those in modified natural cycle (mNC) FET (ovulation triggered by human chorionic gonadotrophin) and stimulated cycle (SC) FET. Objective: To assess the pregnancy outcomes within matched mNC-FET, SC-FET, and AC-FET cycles by using propensity score matching (PSM) in a larger cohort. Methods: A total of 16,946 women who underwent their first autologous FET cycle between July 2014 and July 2017 were evaluated. PSM, using the nearest neighbor matching, were established to adjust the baseline features within the three protocols in proportion of 1:1 (mNC-FET vs. SC-FET, mNC-FET vs. AC-FET, SC-FET vs. AC-FET). Furthermore, there were 3,567, 2,917, and 3,964 cycles compared between matched mNC-FET and SC-FET, mNC-FET and AC-FET, and SC-FET and AC-FET after the PSM, respectively. Results: LBR was significant lower in the AC-FET group than that in the mNC-FET (40.0 vs. 43.3%) and SC-FET groups (40.9 vs. 46.5%). The adjusted odds ratios (95% CIs) were 1.11 (1.00, 1.24) for mNC/AC (P = 0.044) and 0.84 (0.76, 0.92) for AC/SC (P < 0.001), which indicated that the AC-FET group was associated with lowest LBR. The LBR was comparable between matched mNC-FET and SC-FET after adjusting for endometrial thickness. Moreover, a lower clinical pregnancy rate and a higher risk of early pregnancy loss were discovered in AC-FET cycles compared with those in SC-FET. Conclusion: In view of our data, AC used for scheduling FET was associated with lower LBR compared with SC and modified natural cycle. This interpretation requires future verification from well-designed prospective multicenter randomized clinical trials, although the comparisons in our study were conducted in the homogenous population after the PSM.