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Endometrial scratching in patients with unexplained infertility who have a good prognosis for natural conception: a
E E Preesman1, B Bui1, P M Vd Ven2
1Department of Gynaecology & Reproductive Medicine, University Medical Centre Utrecht, Utrecht, The Netherlands.
Study Question:
Does endometrial scratching improve live birth rates in patients with unexplained infertility who have a good prognosis for natural conception (Hunault score ≥ 30%)?
Summary Answer:
The cumulative live birth rate per intention-to-treat (ITT) was 64% and 57% in the endometrial scratch and control group, respectively (not statistically significant).
What Is Known Already:
Endometrial injury (also called endometrial scratching) improves embryo implantation in patients undergoing medically assisted reproduction (MAR). Due to the low quality of evidence in the currently available literature, it is not clear whether endometrial scratching will improve live birth rates in patients with unexplained infertility who have a good prognosis for natural conception.
Study Design, Size, Duration:
A multicentre open-label, randomized controlled trial was conducted at 31 hospitals in the Netherlands between November 2017 and May 2023. A total of 593 patients were randomized to endometrial scratch (intervention group) versus no intervention (control group) at the start of a period of minimum 6 months of natural conception. Follow-up continued 12 months after randomization and subsequently until live birth in the event of a pregnancy.
Participants/Materials, Setting, Methods:
Patients with unexplained infertility with a good prognosis for natural conception (Hunault score ≥ 30%) were eligible. Scratching was performed using an endometrial biopsy catheter (Pipelle de Cornier or similar catheter) covering the entire endometrial cavity. Analyses were performed according to the ITT and the per-protocol (PP) principle, the latter excluding participants who did not receive the allocated intervention. Inverse probability weighting (IPW) was used to account for differences in baseline factors when comparing the subgroups of women in the intervention arm who received the scratch in the follicular phase or the luteal phase with the control arm. As women receiving scratch in the mid-luteal phase were instructed not to become pregnant in the scratch cycle, an additional landmark analysis using IPW was performed where pregnancies in the first cycle were excluded. The primary outcome was pregnancy occurring within 12 months follow-up, leading to live birth.
Main Results And The Role Of Chance:
In total, 593 participants were randomized and assigned to the scratch group or the control group (n = 296 in scratch, n = 297 in control). Two participants were secondarily excluded, and three participants were lost to follow-up (2 withdrew consent; 1 lost to follow-up). After 12 months of follow-up, in the ITT analysis 188/294 (64%) and 168/294 (57%) pregnancies leading to live birth were observed in the scratch and control group, respectively (relative risk (RR): 1.12 [95% CI 0.98-1.28], P = 0.09; risk difference (RD): +6.8% [95% CI -1.1% to +14.7%]). In the PP analysis, 157/259 (61%) and 168/294 (57%) pregnancies leading to live birth were observed in the scratch and control group (RR: 1.06 [95% CI 0.92-1.22], P = 0.41; RD +3.5% [95% CI -4.7% to +11.7%]). Time to pregnancy leading to live birth between the scratch and the control group did not show a statistically significant difference. There were no statistically significant differences in clinical pregnancy, ongoing pregnancy, miscarriage, ectopic pregnancy, multiple pregnancy, termination of pregnancy, and immature birth between the scratch group and the control group. No severe complications due to endometrial scratching occurred.
Limitations, Reasons For Caution:
The scheduled sample size target (792 subjects) was not reached because of suboptimal enrolment due to a lower-than-expected participation rate and competition with a concurrent national study in the same study population.
Wider Implications Of The Findings:
The final analysis of the SCRaTCH-OFO study did not demonstrate a statistically significant effect of endometrial scratching on live birth rates in patients with unexplained infertility and a good prognosis for natural conception. Well-designed meta-analyses and/or trials in different patient phenotypes and under different intervention timings should provide more statistical power to assess a potential clinical benefit of endometrial scratching.
Trial Registration Number:
NL-OMON52881; https://onderzoekmetmensen.nl/nl/trial/52881; https://trialsearch.who.int/Trial2.aspx? TrialID=NL-OMON52881.
Trial Registration Date:
28 September 2017.
Date Of First Patient’S Enrolment:
17 November 2017.