Impact of Endometrial Polyps on Pregnancy Outcomes in Patients with Endometriosis and Infertility: A Systematic Review and Meta-analysis

- Figure 1 shows the selection process for the articles included in the meta-analysis. In total, 743 citations were retrieved from the database. After removing duplicate articles, 523 citations were screened. Subsequently, 508 articles were excluded after screening titles and abstracts. Finally, we carefully reviewed the full text of the remaining 15 articles, 10 of which were included in the meta-analysis. NOS was used to assess the quality of the included studies. - The characteristics of the eligible studies are shown in Table 1. Of the 10 articles included in our meta-analysis, eight were cohort studies[11,14-20] and the remaining two were case-control studies[21,22], including a total of 1,691 patients with EMs and infertility, of whom 651 patients had EP and 1040 did not have EP. All the studies were conducted in China. NOS was used to assess the quality of the included studies. All the included studies were of high quality, as shown in Table 2. Author, Year Study design NO. of sample Follow-up duration (month) Outcomes NOS EMs+EP EMs Lin SH 2018[14] Cohort 129 172 24–36 ①②③④ 8 Wang JL 2016[15] Cohort 60 60 9–44 ①②③④⑤ 6 Chen YH 2018[16] Cohort 33 33 24 ①④⑤ 6 Xu GX 2014[17] Cohort 77 42 18 ① 6 Wang Y 2014[11] Cohort 71 181 9–44 ①②③④⑤ 8 Feng X 2018[18] Cohort 105 143 12–45 ①② 8 Wang JL 2019[19] Cohort 37 65 24 ①②③④⑤ 6 Xu WN 2020[20] Cohort 30 34 36 ①② 8 Li SZ 2017[21] Case-control 50 197 18–24 ① 6 Han Q 2019[22] Case-control 59 113 12 ①②③④⑤ 6 Note. ① , ②, ③, ④ and ⑤ represent follow-up outcomes：Cumulative pregnancy rates; Natural pregnancy rates; Clinical pregnancy rates; Embryonic arrest rates; Live birth rates. EP, endometrial polyps; EMs, endometriosis. Table 1. Study characteristics Author, Year Selection Comparability Outcome Total score Representativeness of the exposed cohort Selection of non-exposed cohort Ascertainment of exposure Outcome of interest not present at the start of the study Study controls for the most important factor Study controls for any additional factor Assessment of outcome Was follow-up long enough for outcomes to occur Adequacy of follow-up of cohorts Lin SH 2018[14] 1 1 1 1 1 0 1 1 1 8 Wang JL 2016[15] 1 1 1 1 1 0 0 1 0 6 Chen YH 2018[16] 1 1 1 1 1 0 0 1 0 6 Xu GX 2014[17] 1 1 1 1 1 0 0 1 0 6 Wang Y 2014[11] 1 1 1 1 1 0 1 1 1 8 Feng X 2018[18] 1 1 1 1 1 0 1 1 1 8 Wang JL 2019[19] 1 1 1 1 1 0 0 1 0 6 Xu WN 2020[20] 1 1 1 1 1 0 1 1 1 8 Li SZ 2017[21] 1 1 1 1 0 0 1 1 0 6 Han Q 2019[22] 1 1 1 1 0 0 0 1 1 6 Table 2. Risk of bias for included studies (score) - Ten studies used cumulative pregnancy rates as an outcome. Our meta-analysis of the 10 articles showed a higher cumulative pregnancy rate in patients with EMs and infertility in the non-EP group (509/1,040, 48.94%) than those in the EP group (277/651, 42.55%). Moderate heterogeneity was observed among the studies (I2 = 74%, P < 0.001). The analysis result using the random effect model found that the combined effect size was OR = 0.81 (95% CI: 0.53–1.25, P = 0.340) (Figure 2). After excluding the study with the smallest sample size, the inter-study heterogeneity was reduced, but the results showed no change. - Seven studies reported natural pregnancy rates. The meta-analysis of these seven articles found that the combined effect size was OR = 1.34 (95% CI: 0.94-1.90, P < 0.001) (Figure 3). There was low heterogeneity among the studies (I2 = 44%, P = 0.100), and the analysis results using the fixed-effect model showed that EP can significantly reduce the natural pregnancy rates in patients with EMs and infertility (46.56% vs. 35.81%). - Five studies reported clinical pregnancy rates. The meta-analysis of these five articles found that the combined effect size was OR = 0.63 (95% CI: 0.48–0.84, P = 0.001) (Figure 4). There was low heterogeneity among the studies (I2 = 0%, P = 0.500), and the analysis results using the fixed-effect model showed that patients with EMs and infertility with EP had lower clinical pregnancy rates (111/356, 31.18%) than those in the non-EP group (243/591, 41.12%). Among them, the definition of clinical pregnancy rates was not explicitly mentioned in Wang JL 2016 and Wang JL 2019 articles[15,19]. - Six studies assessed embryonic arrest rates. The meta-analysis of these six articles found that the combined effect size was OR = 3.10 (95% CI: 1.52–6.32, P = 0.002) (Figure 5). There was low heterogeneity among the studies (I2 = 32%, P = 0.190), and the analysis results using the fixed-effects model showed that the embryonic arrest rates of patients with EMs and infertility in the EP group were higher than those in the non-EP group (5.66% vs. 1.60%). - Four studies reported live birth rates. The meta-analysis of these four articles found that the combined effect size was OR = 0.63 (95% CI: 0.42–0.96, P = 0.03) (Figure 6). There was low heterogeneity among the studies (I2 = 27%, P = 0.25), and the analysis results using the fixed effects model showed that the live birth rate of patients with EMs and infertility in the EP group was 25.40% (48/189), which was lower than that of the non-EP group (99/271, 36.53%). In Wang Y’s article[11], 13 patients were still pregnant, and the pregnancy outcomes were not yet followed up. We attempted to contact the corresponding author by email but failed to reach the author. - The funnel plot exploring the cumulative pregnancy rate difference between patients with EMs and infertility in the EP and non-EP groups was not symmetrical, indicating that the meta-analysis may have had publication bias (Figure 7). As other outcomes were not studied extensively, we did not draw additional funnel plots. - After excluding a single study, there was no obvious change in the outcomes, indicating that the sensitivity is low, and the results of our meta-analysis are robust and reliable. HTML Study Selection Study Characteristics Cumulative Pregnancy Rates Natural Pregnancy Rates Clinical Pregnancy Rates Embryonic Arrest Rates Live Birth Rates Funnel Plot Sensitivity Analyses Competing Interests The authors declare that they have no competing interests. Ethics This research is based on publicly available data and computational analysis, which does not involve any ethical concerns. &These authors contributed equally to this work.