Efficacy of tamoxifen for infertile women with thin endometrium undergoing frozen embryo transfer: a meta-analysis

² Key Laboratory of Birth Defects and Related Diseases of Women and Children, Sichuan University, Ministry of Education, 610041 Chengdu, Sichuan, China

³ Department of Obstetrics and Gynecology, West China Guang-an Hospital, Sichuan University, 638001 Guangan, Sichuan, China

^*Correspondence: fll_guangan@sina.com (Feilang Li)
^† These authors contributed equally.

Clin. Exp. Obstet. Gynecol. 2021, 48(4), 806–811; https://doi.org/10.31083/j.ceog4804129

Submitted: 6 March 2021 | Revised: 21 March 2021 | Accepted: 1 April 2021 | Published: 15 August 2021

This is an open access article under the CC BY 4.0 license (https://creativecommons.org/licenses/by/4.0/).

Abstract

Background: This study aims to compare the effect of tamoxifen (TMX) vs. other regimens on endometrial thickness (EMT), clinical pregnancy, implantation, miscarriage, and live birth rates in women with thin endometrium undergoing frozen-thawed embryo transfer (FET). Methods: We searched the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, and CINAHL from inception to November 2020 and cross-checked the references of relevant articles. We included randomized controlled trials (RCTs) and nonrandomized controlled trials (non-RCTs) to compare TMX with other regimens for endometrium preparation in women with thin endometrium undergoing FET. We pooled weighted mean differences (WMD) with 95% confidence intervals (CI) for continuous variables (EMT) and odds ratios (OR) with 95% CI for binary variables (i.e., clinical pregnancy rate, implantation rate, and first trimester miscarriage rate). Results: An RCT and three controlled trials (2 before-after and 1 retrospective controlled trials) were included in the final review. One study including 154 women and comparing TMX-FET with natural cycle (NC)—FET showed a significant increase in EMT in the TMX cycle (7.87 $\pm{}$ 1.48 mm vs. 6.11 $\pm{}$ 0.98 mm, P $<$ 0.05). Three studies compared the EMT in the TMX and the hormone replacement treatment (HRT) cycles. The pooled analysis showed beneficial effect of TMX on EMT (WMD = 2.06, 95% CI = 1.86–2.27, P $<$ 0.00001). An RCT and a retrospective controlled trial compared TMX and ovulation induction (OI) with Letrozole/human menopause gonadotropin (hMG) for endometrium preparation in women with thin endometrium undergoing FET. No significant difference in clinical pregnancy rates (OR = 1.03, 95% CI = 0.71–1.51), implantation rate (OR = 1.03, 95% CI = 0.76–1.38), or miscarriage rate (OR = 0.91, 95% CI = 0.40–2.06) was observed. No significant difference in EMT was found between TMX and OI with Letrozole/hMG in the included studies. Conclusions: In women with thin endometrium undergoing FET, the use of TMX may result in improved EMT than other regimens. At present, evidence supporting the preferred use of TMX over other regimens as clinical pregnancy rate, implantation rate, or the first trimester miscarriage rate is insufficient.