The effect of endometrial injury on ongoing pregnancy rate in unselected subfertile women undergoing in vitro fertilization: a randomized controlled trial.

STUDY QUESTION: Does endometrial injury in the cycle preceding ovarian stimulation for in vitro fertilization (IVF) improve the ongoing pregnancy rate in unselected subfertile women?

SUMMARY ANSWER: Endometrial injury induced by endometrial aspiration in the preceding cycle does not improve the ongoing pregnancy rate in unselected subfertile women undergoing IVF.

WHAT IS KNOWN ALREADY: Implantation failure remains one of the major limiting factors for IVF success. Mechanical endometrial injury in the cycle preceding ovarian stimulation of IVF treatment has been shown to improve implantation and pregnancy rates in women with repeated implantation failures. There is limited data on unselected subfertile women, especially those undergoing their first IVF treatment.

STUDY DESIGN, SIZE, DURATION: This randomized controlled trial recruited 300 unselected subfertile women scheduled for IVF/ICSI treatment between March 2011 and August 2013. Subjects were randomized into endometrial aspiration (EA) (n = 150) and non-EA (n = 150) groups according to a computer-generated randomization list.

PARTICIPANTS/MATERIALS, SETTING, METHODS: Subjects were recruited and randomized in the assisted reproductive unit at the University of Hong Kong. In the preceding cycle, women in the EA group underwent endometrial aspiration using a Pipelle catheter in mid-luteal phase. All women were treated with a cycle of IVF/ICSI. Pregnancy outcomes were compared.

MAIN RESULTS AND THE ROLE OF CHANCE: There were no significant differences in baseline or cycle characteristics between the groups. There were 209 subjects (69.7%) who were undergoing their first IVF cycle and 91 (30.3%) subjects who had repeated cycles. There was no significant difference in ongoing pregnancy rates [26.7% (40/150) versus 32.0% (48/150); RR 0.833 (95% CI 0.585-1.187), P = 0.375] in the EA and non-EA groups. The implantation rates [32.8% (67/204) versus 29.7% (68/229); RR 1.080 (95% CI 0.804-1.450), P = 0.120], clinical pregnancy rates [34.0% (51/150) versus 38.0 (57/150); RR 0.895 (95% CI 0.661-1.211), P = 0.548], miscarriage rates [30.3% (17/56) versus 18.6% (11/59), RR 1.628 (95% CI 0.838-3.164), P = 0.150] and multiple pregnancy rates [31.3% (16/51) versus 19.3% (11/57), RR 1.626 (95% CI 0.833-3.172), P = 0.154] were all comparable between the EA and non-EA groups. Subgroup analysis in women having first embryo transfer (n = 209) also demonstrated no significant difference in ongoing pregnancy rates, but for women undergoing repeated cycles (n = 91), the on-going pregnancy rate was significantly lower in the EA group than in the non-EA group.

LIMITATIONS, REASONS FOR CAUTION: The study aimed at assessing an unselected population of subfertile women by recruiting consecutive women attending our fertility clinic. However, since the majority of the recruited women (69.7%) were having their first IVF treatments, the results may not be generalizable to all women undergoing IVF.

WIDER IMPLICATIONS OF THE FINDINGS: Previous RCTs and meta-analyses have suggested improved pregnancy rates after pretreatment endometrial injury in women with repeated implantation failure. A recent RCT also showed increased pregnancy rates in unselected subfertile women after endometrial injury, although that study was terminated early and thus underpowered. Our study showed with adequate power that no significant improvement in pregnancy rates was observed after endometrial injury in unselected women undergoing IVF treatment.

STUDY FUNDING/COMPETING INTERESTS: The study was supported by the Small Project Funding 201309176012 of the Committee on Research and Conference Grants, University of Hong Kong. The authors have nothing to disclose.

TRIAL REGISTRATION NUMBER: HKCTR-1646 and NCT 01977976.