A multicentre, randomized, double-blind, placebo-controlled trial of topical oestradiol gel for endometrial regeneration after induced abortion.

Study question: Is topical oestradiol gel effective in promoting endometrial regeneration after a surgical abortion?

Summary answer: Topical oestradiol gel is effective in promoting endometrial regeneration after a surgical abortion with few side-effects.

What is known already: Oestrogen is effective in promoting endometrial regeneration. Transdermal oestrogen has been widely used in clinical practice for endometrial regeneration after induced abortion, but high-level evidence is limited.

Study design, size, duration: We conducted a multicentre, superiority, randomized, double-blind, placebo-controlled trial. Between 9 March 2022 and 21 February 2023, 200 women were assigned in a 1:1 ratio to receive either oestradiol gel (treatment) and or oestradiol gel simulant (control) for 28 days. The participants were scheduled to have their endometrial thickness (mm) measured by ultrasonographic scan at 21-23 days post-abortion. The trial was blinded for participants, investigators, medical staff, and statistical analysts until final unblinding.

Participants/materials, setting, methods: Participants were women undergoing induced abortion within 10 weeks of gestation. A total of 200 participants were enrolled, with 100 in each group. Eighty-eight (88%) in the treatment group and 82 (82%) in the control group completed the study as per the protocol and were included in the per-protocol set (PPS). The intent-to-treat (ITT) analysis included all participants randomized to the study groups and used inverse probability weighting to account for loss to follow-up.

Main results and the role of chance: The ITT analysis showed revealed significantly greater endometrial thickness in the treatment group (mean 8.1 ± 2.5 mm) compared to the control group (mean 6.9 ± 2.1 mm) 21-23 days postabortion (mean difference 1.2 mm, 95% CI 0.7 to 1.9; P < 0.001). The median time to menstrual return was shorter in the treatment group (34 days, inter-quartile range [IQR] 30-38) than in the control group (35 days, IQR 32-42), with a difference of -1 day (95% CI -2.3 to -0.9; P = 0.036). No differences were observed in the timing or volume of bleeding in the first post-abortion cycle. The PPS analysis mirrored the ITT findings. Adverse events were minimal (6% versus 8%), and the blood profile, liver, kidney and coagulation test results were comparable between groups (all P > 0.05).

Limitations, reasons for caution: Loss to follow-up was 11% in the treatment group and 15% of controls, with no significant difference (P > 0.05). Inconsistencies in the timing of the ultrasonographic scans may have affected the accuracy of endometrial thickness measurements.

Wider implications of the findings: Our findings suggest that topical oestrogen supplementation immediately after abortion within the first 10 weeks of gestation improves endometrial regeneration and growth, thereby potentially increasing the chances of a successful subsequent pregnancy. Clinical application of these findings may improve endometrial health management practices and provide a perspective on fertility treatment and women's reproductive health.

Study funding/competing interest(s): This study was supported by a grant (FW-HKKT2021111501900) from Jianmin Pharmaceutical Group Co., Ltd (JMPG), Wuhan, Hubei, China. Both the oestradiol gel and the simulant were provided by JMPG. The funding source had no role in the study. X.Y.L. reports JMPG grant funding paid to their institutions. All other authors declare no competing interests.

Trial registration number: CHiCTR2100053565.

Trial registration date: 24 November 2021.

Date of first patient’s enrolment: 9 March 2022.