scholarly journals Evaluation of Pregnancy Outcomes of Vitrified-Warmed Blastocyst Transfer before and after Endometrial Receptivity Analysis in Identical Patients with Recurrent Implantation Failure

2021 ◽  
pp. 1-7
Author(s):  
Yuta Kasahara ◽  
Tomoko Hashimoto ◽  
Ryo Yokomizo ◽  
Yuya Takeshige ◽  
Koki Yoshinaga ◽  
...  

Background:The clinical value of personalized embryo transfer (pET) guided by the endometrial receptivity analysis (ERA) tests for recurrent implantation failure (RIF) cases is still unclear. The aim of this study is to clarify the efficacy of ERA leading to personalization of the day of embryo transfer (ET) in RIF patients. Methods: A retrospective study was performed for 94 patients with RIF who underwent ERA between July 2015 and December 2019. Pregnancy outcomes in a previous vitrified-warmed blastocyst transfer (previous VBT) and a personalized vitrified-warmed blastocyst transfer (pVBT) in identical patients were compared. The details of each pVBT were further analyzed between patients in a non-displaced group, which indicated “receptive” cases in ERA results and those who were in the displaced group, which indicated “non-receptive” cases. Results:When the pregnancy rate, both per patient and per transfer cycle, of previous VBT and pVBT were compared, a significant increase in pVBT was observed between the two methods (5.3% vs. 62.8%, 4.4% vs. 47.9%, respectively). The pregnancy rates, implantation rates, and clinical pregnancy rates of the first pVBT were significantly higher in the displaced group than the non-displaced group. The cumulative ongoing pregnancy rate of the displaced group tended to be higher compared to that of the non-displaced group in the first pVBT, although the difference was not statistically significant (51.0% vs. 31.1%, [Formula: see text] = 0.06). Conclusions:Our study demonstrates that pVBT guided by ERA tests may improve pregnancy outcomes in RIF patients whose window of implantation (WOI) is displaced, and its effect may be more pronounced at the first pVBT. The displacement of WOI may be considered to be one of the causes of RIF, and its adjustment may contribute to the improvement of pregnancy outcomes in RIF patients.

2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
Y Dong ◽  
Y Jia ◽  
Y Sha ◽  
L Diao ◽  
S Cai ◽  
...  

Abstract Study question To evaluate whether the pregnancy outcomes could be improved in implantation failure patients by endometrial receptivity array, endometrial immune profiling, or a combination of both. Summary answer There was no statistical difference between different endometrial receptivity evaluation and treatment in improving the clinical pregnancy rate. What is known already Both endometrial receptivity array and endometrial immune profiling were promised to improve the endometrial receptivity and subsequent clinical pregnancy. However, less is known about the efficiency between each other and whether the combination could further enhance their clinical value. Study design, size, duration Between November 2019 and September 2020, 143 women with a history of at least two or more consecutive implantation failure in IVF/ICSI treatment in Chengdu Xinan Gynecology Hospital were included. They were divided into three groups: ‘ERA + Immune Profiling’ (n = 70), ‘Immune Profiling’ (n = 41), and ‘ERA’ (n = 32). Participants/materials, setting, methods Inclusion criteria were age ≤ 38, with normal uterus and uterine cavity. All patients were suggested to evaluate endometrial receptivity by ERA test (Igenomix, Valencia, Spain) and endometrial immune profiling based on immunohistochemistry simultaneously, who would be free to choose each or both evaluation approaches. Personal Embryo Transfer and/or personal medical care were adopted according to evaluation results. Clinical pregnancy was confirmed by gestational sacs observed under ultrasonography. Main results and the role of chance The overall prevalence of displaced window of implantation (WOI) is 84.3%, and nearly 74.8% (83/111) patients were diagnosed as endometrial immune dysregulation. Clinical Pregnancy rate and embryonic implantation rate decreased in the ‘Immune Test’ groups, but without a statistical difference (P = 0.311, and 0.158, respectively). Multivariable logistic regression analysis showed that different endometrial receptivity evaluation and treatment was not associated the clinical pregnancy rate, suggesting the performance of different endometrial receptivity evaluation and treatment is similar in improving the clinical pregnancy rate. Neither the immune profiling (CD56, P = 0.591; FOXP3, P = 0.195; CD68, P = 0.820; CD163, P = 0.926; CD1a, P = 0.561; CD57, P = 0.221; CD8, P = 0.427; CD138 CE, P = 0.372) nor histologic endometrial dating defined by Noyes criteria (P = 0.374) were associated with ERA phases. Limitations, reasons for caution Although the selection of evaluation approaches was based on patients’ willingness, the variances of baseline characteristics and immune profiling existed in different groups. The immunological treatment efficacy based on immune profiling was not evaluated before embryo transfer. Wider implications of the findings: To our knowledge, this is the first study comparing the pregnancy outcomes after two typical endometrial receptivity evaluation approaches. The findings highlight the unsubstitutability for each assessment, indicating that both asynchronous and pathological WOI contribute to implantation failure. Trial registration number X2019004


2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
Y Jia ◽  
Y L Sha ◽  
Z Qiu ◽  
Y H Guo ◽  
A X Tan ◽  
...  

Abstract Study question To quantify the effectiveness of endometrial receptivity analysis (ERA)-guided personalized embryo transfer (pET) in Chinese women. Summary answer ERA-guided pET may remarkably improve pregnancy and implantation rates among Chinese women with Recurrent implantation failure (RIF). What is known already RIF is a major cause of infertility, and endometrial receptivity is widely accepted to impact implantation failure. Precision prediction of the WOI, the time when the endometrium is most receptive to the implantation of the embryo, is, therefore, of great significance to improve implantation prospects. Previous studies have shown the effectiveness of ERA for the prediction of the WOI, and how pET, timed by ERA, improves implantation and pregnancy rates; however, the efficacy of ERA-guided pET remains unknown for Chinese women. Study design, size, duration Patients in Chengdu Xi’nan Gynecology Hospital (Chengdu, China) who were undergoing frozen embryo transfer (FET) at the blastocyst stage on day five or day six during the period from November 2019 through September 2020 were recruited for this study. A total of 145 eligible patients were included in the study and assigned to the ERA group (n = 67) or the control group (n = 78). Clinical pregnancy outcomes were compared between the two groups. Participants/materials, setting, methods Endometrial specimens were collected the from ERA group. Total RNA was extracted from endometrial specimens, the transcriptomic sequencing data were processed using RNA-Seq and the endometrial receptivity status was assessed by the ERA predictor. The endometrium was classified as receptive or non-receptive according to the ERA assessment, and pET was done at the time determined by ERA in the ERA group. Subjects in the control group did not receive ERA and underwent blastocyst transfer normally. Main results and the role of chance The demographic and clinical characteristics were comparable between the ERA and control groups (P > 0.05). The ERA test identified 10.45% of samples as receptive and 89.55% of samples as non-receptive in the ERA group, with 70.15% of samples presenting a pre-receptive profile. We observed higher cumulative pregnancy (74.63% vs. 64.10%) and cumulative implantation rate (47.32% vs. 21.68%) rates, and a lower biochemical pregnancy rate (18.00% vs. 34.00%) in the ERA group when compared to the control group (P < 0.05). Additionally, we found higher pregnancy (67.16% vs. 39.74%) and implantation (46.54% vs. 16.94%) rates as well as a lower biochemical pregnancy rate (17.78% vs. 45.16%) after the first ERA test in the ERA group when compared to the control group (P < 0.01). Limitations, reasons for caution First, this is a retrospective analysis, which is relatively more biased than prospective clinical trials. Second, the study sample is considerably small. Third, only 10.45% of the subjects were identified as presenting a receptive profile, which limits the comparisons of clinical outcomes between patients with receptive and non-receptive endometria. Wider implications of the findings: This study demonstrates that the ERA test helps to determine the optimal timing for embryo transfer, improve pregnancy and implantation rates in patients with RIF, and guides the clinical application of the ERA test. Trial registration number approval No. 2020–018


2021 ◽  
Vol 16 (1) ◽  
pp. 79-85
Author(s):  
Ioan BOLEAC ◽  
◽  
Manuela NEAGU ◽  
Anca CORICOVAC ◽  
Dorina CODREANU ◽  
...  

Recurrent implantation failure is represented by the failure to achieve a clinical pregnancy after transfer of at least 4 good-quality embryos in a minimum of 3 fresh or frozen cycles in a woman under the age of 40 years. One of the recent approaches in studying the window of implantation was building the expression profile of the genes of the endometrial cells. We performed a retrospective study which investigated if endometrial receptivity tests improved the outcomes of IVF procedures in patients with recurrent implantation failure. We enrolled 47 couples with RIF and divided them in 2 groups: the first group of 22 couples performed the ERA test and the embryo transfer according to the result of the test; the second group of 27 couples had the embryo transfer done without the ERA test. Our conclusion was that the ERA test did not improve the outcomes for patients with recurrent implantation failure.


2020 ◽  
Author(s):  
Meiling Yang ◽  
li Lin ◽  
Chunli Sha ◽  
Taoqiong Li ◽  
Wujiang Gao ◽  
...  

Abstract Background: In recent years, there have been emerging many reports on the pregnancy outcomes of fresh blastocyst transfer (BT) and freeze-thaw BT, but these couclusions are controversial and incomplete. To compare the pregnancy outcomes, maternal complications and neonatal outcomes of fresh and frozen-thawed BT in vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI) cycles, we conducted a meta-analysis. Methods: A meta-analysis was conducted by searching PubMed, Embase, and Cochrane Library until January 2020. Data were extracted independently by two authors. Results: 42 studies, including 12 randomized controlled trials (RCT) met the inclusion criteria. Fresh BT showed lower implantation rate (IR), pregnancy rate (PR), ongoing pregnancy rate (OPR) and higher eptopic pregnancy rate (EPR) compared with frozen-thawed BT consistent with the results of RCT. The risks of moderate or severe ovarian hyperstimulation syndrome (OHSS), placental abruption (PA) and preterm were higher in fresh BT than in the frozen-thawed BT. The risk of pregnancy-induced hypertension (PIH) and pre-eclampsia was decreased in fresh BT , however, no significant differences of risks for PIH, pre-eclampsia, OHSS, and preterm was found between the two group in the 2 RCT included. Compared with frozen-thawed BT, fresh BT appears to be associated with small for gestational age (SGA) and low birth weight (LBW). No differences in the incidences of neonatal mortality and neonatal malformations were observed between fresh and frozen-thawed BT. Conclusions: In summary, Considering the higher IR, PR, OPR, lower EPR, and the decreased risks of OHSS, PA and preterm, as well as the incidences of SGA and LBW in frozen-thawed BT, this meta-analysis indicates that frozen-thawed BT may be a better choice for mothers and babies compared with fresh BT. Key words: Fresh blastocyst transfer, frozen thawed blastocyst transfer, pregnancy outcome, maternal complications, neonatal outcomes


2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Meiling Yang ◽  
Li Lin ◽  
Chunli Sha ◽  
Taoqiong Li ◽  
Wujiang Gao ◽  
...  

Abstract Background In recent years, there have been many reports on the pregnancy outcomes of fresh blastocyst transfer (BT) and frozen-thawed BT, but the conclusions are controversial and incomplete. To compare the pregnancy outcomes, maternal complications and neonatal outcomes of fresh and frozen-thawed BT in the context of in vitro fertilization or intracytoplasmic sperm injection (IVF/ICSI) cycles, we conducted a meta-analysis. Methods A meta-analysis was conducted by searching the PubMed, Embase, and Cochrane Library databases through May 2020. Data were extracted independently by two authors. Results Fifty-four studies, including 12 randomized controlled trials (RCTs), met the inclusion criteria. Fresh BT was associated with a lower implantation rate, pregnancy rate, ongoing pregnancy rate, and clinical pregnancy rate and higher ectopic pregnancy rate than frozen-thawed BT according to the results of the RCTs. The risks of moderate or severe ovarian hyperstimulation syndrome, placental abruption, placenta previa and preterm delivery were higher for fresh BT than for frozen-thawed BT. The risk of pregnancy-induced hypertension and pre-eclampsia was lower for fresh BT; however, no significant differences in risks for gestational diabetes mellitus and preterm rupture of membrane were found between the two groups. Compared with frozen-thawed BT, fresh BT appears to be associated with small for gestational age and low birth weight. No differences in the incidences of neonatal mortality or neonatal malformation were observed between fresh and frozen-thawed BT. Conclusions At present there is an overall slight preponderance of risks in fresh cycles against frozen, however individualization is required and current knowledge does not permit to address a defintive response.


2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
S Ahuja ◽  
A Taranissi ◽  
M Taranissi

Abstract Study question Do the serum progesterone levels on the day of the endometrial receptivity analysis (ERA) biopsy correlate with the results of the ERA? Summary answer Serum progesterone levels on the day of the endometrial receptivity analysis biopsy do not correlate with the biopsy results. What is known already Endometrial receptivity is a time sensitive window characterised by maturation of the endometrium, during which the trophectodermal cells attach to the endometrial cells and invade the endometrial stromal vasculature. Progesterone is an essential element for receptivity and pregnancy. There is no consensus regarding the optimal progesterone levels in the luteal phase, for a successful pregnancy. Endometrial receptivity analysis is a diagnostic tool developed by profiling the transcriptome of over 238 genes that are expressed at different stages of the endometrial cycle. The results are reported as receptive, pre-receptive, early receptive, etc and are used to direct a personalised embryo transfer. Study design, size, duration We report a prospective study of 30 patients with a history of recurrent implantation failure (RIF). They underwent ERA testing in a medicated cycle, between early 2018 and late 2020. Participants/materials, setting, methods A large proportion of the patients we treat in our clinic (ARGC) have recurrent implantation failure. Thirty patients with RIF underwent ERA testing in a medicated cycle.They all followed the same protocol with down regulation, followed by estrogenic preparation for about 12–14 days, followed by progesterone for about 120 hours. An endometrial biopsy was taken at about 120 hours after progesterone exposure. Main results and the role of chance An ERA result was available on 28/30 patients. Eighteen were reported to be pre-receptive, seven receptive, 3 early receptive and 2 could not be analysed. The progesterone levels within 24 hours of the biopsy for the pre-receptive group ranged from 21.2–472 nmol/l, for the receptive group ranged from 27.8–152 nmol/l and for the early receptive group ranged from 54.9–162 nmol/l. Though the number of cases is small, we found no co-relation between the serum progesterone levels with the ERA results. Eighteen women underwent an embryo transfer based on the ERA results (pET-personalised embryo transfer). Eleven were positive with four live births, one early ongoing pregnancy, three miscarriages, one ectopic pregnancy, two biochemical pregnancies and seven negative results. Seven women had euploid embryo transfers-three had live births, one is viable at 11 weeks, one had a missed miscarriage and two were negative. There are no studies correlating the serum progesterone levels and the ERA results. In practice, we plan embryo transfers for women in frozen cycles by monitoring the serum progesterone levels alongside the day of the cycle. Hence, we wanted to review if the combination of the progesterone levels along with biopsy results would allow us the improve the results further. Limitations, reasons for caution This is a small study. Larger datasets are required to draw meaningful conclusions. Wider implications of the findings: If the above findings are confirmed by larger studies, we may not need to monitor serum progesterone levels during ERA biopsy cycles. Trial registration number NA


2021 ◽  
Vol 12 (1) ◽  
pp. 407-415
Author(s):  
Dalal M. Al Jarrah ◽  
Manal Taha Al Obaidi ◽  
Itlal J. AL Asadi

Endometrial receptivity plays a basic role in successful embryo implantation and pregnancy outcomes and can be assessed by many of non-invasive markers. Our study evaluated the impact of two of these markers specifically serum progesterone and endometrial thickness at embryo transfer day in prediction pregnancy outcomes on (60) patients attempting medicated frozen embryo transfer (FET) cycles. All patients were received sequential estrogen & progesterone medications for endometrial preparation then submitted to measurements of endometrial thickness (EMT) by transvaginal-ultrasound (TV-US) & serums progesterone (P) analysis at the embryo transfer day, thereafter day 3 verified-thawed embryos grades (A±B) were transferred. Compacted (decreased) EMT was seen in 48.3% of patients with higher pregnancy rate (PR) of 58.6%t than non-compacted EMT (no change or increased) which was seen in 51.7% of patients with (PR) of 29.0%, (P value=0.021). However ongoing pregnancy rate (Ong PR) not differed significantly between both groups (44.8% in compacted vs 25.8% in non-compacted, P value=0.053), also the means of serum P not differed between pregnant and non-pregnant patients (P value=0.374). ROC curves for Ong PR prediction in relations to endometrial compaction & serum progesterone at embryo transfer day were poor (AUC= 0.630, & AUC=0.576, respectively). This study suggested that endometrial compaction or serum P levels measurements at embryo transfer day were poor predictors for ongoing pregnancy where any kind of EMT changes (decreased or not) seen after P administration not significantly affect pregnancy outcomes in frozen-thaw cycles of cleavage stage embryos transfer.


2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
C Maignien ◽  
B Mathilde ◽  
B Valérie ◽  
C Ahmed ◽  
C Charles ◽  
...  

Abstract Study question Is there a relationship between progesterone levels on the day of frozen blastocyst transfer and ongoing pregnancy rate (OPR), in hormonal replacement therapy (HRT) cycles? Summary answer Women undergoing HRT-frozen embryo transfer with progesterone levels≤9.76ng/ml on the day of blastocyst transfer had a significantly lower OPR than those with progesterone levels>9.76 ng/ml. What is known already The importance of serum progesterone levels around the time of frozen embryo transfer (FET) is a burning issue, in view of the growing number of FET worldwide. However, the optimal range of serum progesterone levels is not clearly determined and discrepancies arise from the current literature. Study design, size, duration: Observational cohort study with 915 patients undergoing HRT-FET at a tertiary care university hospital, between January 2019 and March 2020. Participants/materials, setting, methods Patients undergoing single autologous blastocyst FET under HRT using exogenous estradiol and vaginal micronized progesterone for endometrial preparation. Women were only included once during the study period. The serum progesterone level was measured in the morning of the FET, in a single laboratory. The primary endpoint was OPR beyond pregnancy week 12. Statistical analysis was conducted using univariate and multivariate logistic regression models. Main results and the role of chance Mean serum progesterone level on the day of FET was 12.90 ± 4.89 ng/ml). The OPR was 35.5% (325/915) in the overall population. Patients with a progesterone level ≤ 25th percentile (≤9.76ng/ml) had a significantly lower OPR and a higher miscarriage rate (MR) compared with women with progesterone level over Centile 25 (29.6% versus 37.4%; p = 0.033 and 34.8% versus 21.3%; p = 0.008, respectively). After adjustment for the potential confounders in a multivariate analysis, a serum progesterone level ≤ 9.76 ng/ml on the day of FETand FET of a Day 6-blastocyst (versus Day 5-blastocyst) were found as independent risks factor of lower OPR. Limitations, reasons for caution The main limitation of our study is linked to its observational design. Extrapolation of our results to other laboratories, or other routes and/or doses of administering progesterone also needs to be validated. Wider implications of the findings: This study suggests that a minimum serum progesterone level is needed to optimize reproductive outcomes in autologous blastocyst FET, in HRT-cycles. Further studies are needed to evaluate if modifications of progesterone routes and/or doses may improve pregnancy chances, in an approach to individualize the management of ART patients. Trial registration number NA


2021 ◽  
Vol 36 (Supplement_1) ◽  
Author(s):  
M Alvarez ◽  
A Racca ◽  
S García ◽  
F Martínez ◽  
I González-Foruria ◽  
...  

Abstract Study question Does progesterone-supplementation (PS) from the day of β-hCG assessment improve pregnancy rates in embryo transfer-under hormonal replacement therapy (ET-HRT) in patient with Progesterone (P)<10.6 ng/mL? Summary answer Reduced P on the β-hCG day is associated with lower pregnancy-rates and higher miscarriage-rate. PS from the same day showed significant increase of reproductive outcomes. What is known already Up until now, in ART, very little has been done to understand whether the P intake should be personalized during the luteal phase. Most recent studies on the topic showed that low P levels on the day of ET-HRT or on the day before are associated with decreased pregnancy rates; however, when low P values are supplemented from the day before embryo-transfer (ET), similar results to cases with adequate P are reported. Nevertheless, little is known about the association between low P level, on the day of β-hCG (P- β-hCG) and PS from this day in ET-HRT, and pregnancy outcomes. Study design, size, duration This is a single centre, cohort, retrospective study conducted at a university-affiliated fertility centre between January 2018 and June 2020 where PS took place from the day of positive β-hCG determination when P < 10.6 ng/mL. In total 789 ET-HRT cycles were analysed of which 239 were performed in both fresh and frozen heterologous ET-HRT (het-ET), 336 in homologous ET-HRT (hom-FET) and 214 in euploid ET-HRT (eu-FET) after preimplantation genetic testing for aneuploidies IVF cycles (PGT-A). Participants/materials, setting, methods Women undergoing ET-HRT with normal P (>10.6ng/mL) on the day before ET were screened for P on the day of β-hCG. All women received vaginal P 200 mg/8 hours for the second part of HRT. PS was performed by adding P to the HRT when P- β-hCG was considered low (<10.6 ng/mL). Primary outcome: ongoing-pregnancy-rate (OPR); secondary outcome: miscarriage-rate (MR). Both were evaluated by considering PS on the day of β-hCG as a categorical variable. Main results and the role of chance Patients characteristics were comparable between groups (het-ET, hom-FET and eu-FET) although significantly lower body mass index was found when P- β-hCG>10.6 ng/mL compared to the subgroup with P- β-hCG<10.6 ng/mL and no PS (p = 0.012). Overall clinical pregnancy rate was 52.1% with no-significant differences between groups (48.5% in het-ET, 52.9% in hom-FET and 54.7% in eu-FET). P- β-hCG was considered as adequate in 75.7% (311/411) ET-HRT with positive β-hCG and low in 24.3% (100/411), with no differences between groups. In case of positive β-hCG and P- β-hCG >10.6 ng/mL, OPR was 83.6% and MR was 16.4%, with no-significant differences between groups. Among the 100 low P- β-hCG, 80 ET-HRT received PS. In this subgroup OPR was 96.2% and MR was 3.8%, with no-significant differences between groups. In 20 out of 100 ET with P- β-hCG <10.6 ng/mL, no PS was added for different reasons. This group showed the lowest OPR (30%) and the highest MR (70%), again with no between-group differences according to het-ET, hom-FET or eu-FET. Miscarriage rate was significantly higher (p < 0.001) when P- β-hCG was <10.6 ng/mL and no PS was added to HRT compared to P- β-hCG <10.6 ng/mL but with PS, and also compared to the P- β-hCG >10.6 ng/mL group. Limitations, reasons for caution The main limitation of the study is due to its retrospective nature and the small sample of patients with P- β-hCG<10.6 ng/mL that was not supplemented. Furthermore, the cut-off of P- β-hCG was arbitrarily decided upon previous studies, and lastly different routes of administration were considered for the PS. Wider implications of the findings: The results of this study showed that individualization of Progesterone supplementation in ET-HRT may be a crucial turn point in order to increase the pregnancy rates and decrease the miscarriage rates. An adequate PS should be considered in case of low P- β-hCG levels for both het-ET, hom-FET and eu-FET. Trial registration number Not applicable


2019 ◽  
Vol 36 (12) ◽  
pp. 2471-2479 ◽  
Author(s):  
Tomoko Hashimoto ◽  
Koichi Kyono

Abstract Purpose To analyze the pregnancy outcomes of IVF patients presenting eubiotic or dysbiotic endometrium at the time of embryo transfer and to analyze what bacterial profiles are suitable for embryo implantation. Methods Ninety-nine IVF patients under 40 years old undergoing vitrified-warmed blastocyst transfer in HRT cycle had concurrent endometrial microbiome analysis. Samples from the endometrium were taken from the participants at the time of mock transfer; the bacterial profiles at genus level and percentage of lactobacilli in the endometrium of the patients were analyzed. Results Thirty-one cases (31.3%) had dysbiotic endometrium. The background profiles, pregnancy rates per transfer (52.9% vs 54.8%), and miscarriage rates (11.1% vs 5.9%) were comparable between patients with eubiotic or dysbiotic endometrium. Major bacterial genera other than Lactobacillus detected in the dysbiotic endometrium were Atopobium, Gardnerella, and Streptococcus. Some patients achieved ongoing pregnancies with 0% Lactobacillus in the endometrium. The endometrial bacterial profiles of pregnant cases with dysbiotic endometrium were comparable with those of non-pregnant cases. Conclusion Analyzing microbiota at the species-level resolution may be necessary for identifying the true pathogenic bacteria of the endometrium and avoiding over-intervention against non-Lactobacillus microbiota. Further studies are necessary for analyzing the mechanism of how the pathogenic bacteria affect embryo implantation.


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