The relationship and optimal threshold of endometrial thickness with early clinical pregnancy in frozen embryo transfer cycles

A retrospective cohort study to examine factors affecting live birth after hysteroscopic treatment of intrauterine adhesions

OBJECTIVE

To evaluate independent factors that affect the chance of live birth (LB) after hysteroscopic adhesiolysis in patients with intrauterine adhesions.

DESIGN

Retrospective cohort study.

SETTING

Hysteroscopic center of Fuxing Hospital in Beijing, China.

PATIENT(S)

Patients diagnosed with Asherman syndrome between June 2020, and February 2022.

INTERVENTION(S)

Hysteroscopic adhesiolysis is followed by a second look hysteroscopy to assess the outcome and follow-up for a year.

MAIN OUTCOME MEASURE(S)

Live birth rate (LBR) without the use of assisted reproductive technologies at 12-month follow-up.

RESULT(S)

Of the 544 women included in the cohort, the pregnancy rate at the end of 1 year of follow-up was 47.6% (95% confidence interval [CI] 45.5%-49.7%), and the LBR was 41.0% (95% CI 38.9%-43.1%). Stepwise multiple logistic regression analysis identified three independent predictors of LB in decreasing order of significance: increase in menstrual flow after surgery (odds ratio [OR] 3.69, 95% CI 1.77-8.21), postoperative endometrial thickness in the midluteal phase (OR 1.53, 95% CI 1.31-1.80), and the severity of recurred adhesion at second-look hysteroscopy (OR 0.62, 95% CI 0.50-0.76). Among subjects with good independent prognostic factors, namely, increased menstrual flow after surgery, postoperative endometrial thickness in the midluteal phase >6 mm, and no or minimal recurrence of adhesions at second-look hysteroscopy, the LBR was 69.0% (95% CI 65.4%-72.6%). On the other hand, in women (n = 26) without any of the three good prognostic factors, none had a successful LB (0).

CONCLUSION(S)

Overall, the LBR after treatment for Asherman syndrome was 41.0%. The prognosis is dependent on three outcome measures after surgery, namely, improvement in menstrual flow, postoperative endometrial thickness, and the minimal degree of recurrent adhesions at second-look hysteroscopy.

Thick endometrium is associated with hypertensive disorders of pregnancy in programmed frozen-thawed embryo transfers: a retrospective analysis of 2,275 singleton deliveries

OBJECTIVE

To investigate whether endometrial thickness (EMT) acts as a contributing factor to adverse perinatal outcomes in programmed frozen-thawed embryo transfer (FET) cycles.

DESIGN

Retrospective cohort study.

SETTING

University-based reproductive medical center.

SUBJECT

The study included singleton live births resulting from programmed FET cycles that took place between January 2017 and April 2022 (N = 2,275 cycles).

EXPOSURE

The EMT measurement conducted on the day of progesterone initiation was utilized. Programmed FET cycles with EMT <7 mm were excluded from consideration. All included subjects were divided into 4 groups on the basis of the 10th, 50th, and 90th percentiles of EMT: group Ⅰ (EMT ≤8 mm, n = 193), group Ⅱ (EMT = 8.1-10 mm, n = 1,261), group Ⅲ (EMT = 10.1-12 mm, n = 615), and group Ⅳ (EMT >12 mm, n = 206). After adjusting for patient demographics and FET parameters, logistic regression analysis and restricted cubic spline were used to investigate the relationship between EMT and perinatal outcomes. The group Ⅱ (EMT = 8.1-10 mm) served as a reference.

MAIN OUTCOME MEASURE(S)

The primary outcome measure was the hypertensive disorders of pregnancy (HDP). Secondary outcomes included gestational diabetes mellitus, cesarean delivery, placenta previa, premature rupture of membrane, birthweight, preterm birth, low birthweight, macrosomia, small for gestational age, large for gestational age and neonatal morbidity.

RESULTS(S)

The incidence of HDP was substantially elevated in group Ⅳ when compared with the other groups (5.7% vs. 4.1% vs. 5.7% vs. 9.7% for groups Ⅰ-Ⅳ, respectively). In addition, group I displayed a higher incidence of cesarean deliveries, whereas both group I and group IV exhibited an elevated prevalence of placenta previa. After adjusting for confounding factors, patients in group IV exhibited a significantly increased risk of HDP (adjusted odds ratio [OR] = 2.03, 95% confidence interval [CI] 1.13-3.67) as compared with patients in the reference group. The restricted cubic spline model revealed a nonlinear association between EMT and the odds of HDP on continuous scales. In comparison to women with an EMT of 9.5 mm, there was no significant change in the risk of HDP in women with EMT between 7 and 11 mm, as indicated by adjusted ORs of 1.37 (95% CI 0.41-4.52), 1.34 (95% CI 0.73-2.47), 1.13 (95% CI 0.79-1.62), 1.04 (95% CI 0.87-1.25), and 1.46 (95% CI 0.81-2.65), respectively. However, the risk of HDP was significantly higher in women with EMT ranging from 12 to 15 mm, with adjusted ORs of 1.86 (95% CI 1.03-3.35), 2.33 (95% CI 1.32-4.12), 2.92 (95% CI 1.52-5.60), and 3.62 (95% CI 1.63-8.04), respectively.

CONCLUSION(S)

This study demonstrated a noteworthy association between EMT and adverse perinatal outcomes during the programmed FET cycles. Specifically, a thick endometrium (EMT >12 mm) was independently associated with an increased risk of developing HDP, whereas the optimal EMT for reducing the risk of HDP was at around 9-10 mm.

A critical appraisal of studies on endometrial thickness and embryo transfer outcome

A receptive endometrium is required for successful embryo implantation. Endometrial thickness, as measured by ultrasonography, is the most commonly used marker of endometrial receptivity in assisted reproductive technology cycles. Several factors simultaneously affect both endometrial thickness and probability of live birth, including age, oestradiol concentration and oocyte number, among others. Most of the studies investigating a relationship between endometrial thickness and embryo transfer outcomes are retrospective and do not adequately address confounding factors, in addition to other limitations. Despite multiple meta-analyses and studies with large numbers of cycles, controversy still exists. The difference between the results from prospective and retrospective studies is also striking. This article presents a critical appraisal of the studies on endometrial thickness and embryo transfer outcomes in order to highlight methodological issues and how they can be overcome in future studies. Currently available evidence does not seem to support a modification of management just because endometrial thickness is below an arbitrary threshold.

Association between endometrial blood and clinical outcome in frozen single blastocyst transfer cycles

Background: The success of embryo transfer cycle depends mainly on the quality of embryo and endometrial receptivity. Ultrasound examination is still the most widely used non-invasive evaluation method for its advantages of convenience, non-invasiveness and repeatability. Ultrasound-measured endometrial blood flow is one of the important evaluation indicators of morphology. Aims: To investigate the effect of the number of endometrial blood flow branches on pregnancy outcome of frozen-thawed embryo transfer cycles which have undergoing hormone replacement therapy (HRT-FET). Material and methods: A retrospective cohort study was performed looking at a total of 1390 HRT-FET cycles from our reproductive medicine center between January 2017 to December 2021, which transferred one blastocyst frozen on day 5 with good quality in morphology. Associations between endometrial blood flow branches and pregnancy outcomes were evaluated with multivariable linear regression analysis. Results: The number of endometrial blood flow branches was independently associated with clinical pregnancy (OR 1.10; 95% CI 1.02-1.20). After adjusting for potential confounders, the effect size (odds ratio) was 1.09 (95% CI 1.00-1.19), and the results showed that the clinical pregnancy rate and live birth rate of T2 and T3 groups were significantly higher than those in group T1 (p < 0.05). Subgroup analysis showed that a consistent association between the endometrial blood flow branches and clinical pregnancy in all subgroups. Conclusion: Our study provided evidence for the influence of endometrial blood flow on pregnancy outcomes. There may be an independent association between the number of endometrial blood flow branches and pregnancy outcomes in frozen-thawed single blastocyst transfer cycles.

Nomogram prediction for the prediction of clinical pregnancy in Freeze-thawed Embryo Transfer

BACKGROUND

This study aimed to identify multiple endometrial receptivity related factors by applying non-invasive, repeatable multimodal ultrasound methods. Combined with basic clinical data, we further established a practical prediction model for early clinical outcomes in Freeze-thawed Embryo Transfer (FET).

METHODS

Retrospective analysis of clinical data of infertility patients undergoing FET cycle in our Center from January 2017 to September 2019. Receiver operating characteristic (ROC) curve and decision curve analyses were performed by 500 bootstrap resamplings to assess the determination and clinical value of the nomogram, respectively.

RESULTS

A total of 2457 FET cycles were included. We developed simple nomograms that predict the early clinical outcomes in FET cycles by using the parameters of age, BMI, type and number of embryos transferred, endometrial thickness, FI, RI, PI and number of endometrial and sub-endometrial blood flow. In the training cohort, the area under the ROC curve (AUC) showed statistical accuracy (AUC = 0.698), and similar results were shown in the subsequent validation cohort (AUC = 0.699). Decision curve analysis demonstrated the clinical value of this nomogram.

CONCLUSIONS

Our nomogram can predict clinical outcomes and it can be used as a simple, affordable and widely implementable tool to provide guidance and treatment recommendations for FET patients.

The Effects of Endometrial Thickness on Pregnancy Outcomes of Fresh IVF/ICSI Embryo Transfer Cycles: An Analysis of Over 40,000 Cycles Among Five Reproductive Centers in China

OBJECTIVE

To investigate the effects of endometrial thickness (EMT) on pregnancy outcomes on hCG trigger day in fresh in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) cycles.

METHODS

A total of 42,132 fresh cycles between 1 January 2013 and 31 December 2019 were included in this retrospective cohort study. Data were collected from five reproductive centers of large academic or university hospitals in China. All patients were divided into different groups according to their endometrial thickness on hCG trigger day. Multivariate regression analysis, curve fitting and threshold effect analysis were performed.

RESULTS

After adjusting for age, body mass index, infertility type, number of embryos transferred, number of retrieved oocytes and COS (controlled ovarian stimulation) protocols, significant associations were found between endometrial thickness and clinical pregnancy rate (adjusted odds ratio [aOR]: 1.05; 95% confidence interval [CI]: 1.06-1.08, P < 0.0001), live birth rate (aOR: 1.04; 95% CI: 1.03-1.05, P < 0.0001) as well as miscarriage rate(aOR: 0.96; 95% CI: 0.94 - 0.98, P < 0.0001). When the endometrial thickness was less than 12mm, the clinical pregnancy rate and live birth rate were increased significantly by 10% and 9%(OR:1.10; 95%CI: 1.08-1.12, OR:1.09; 95%CI: 1.07-1.11), respectively, along with the increase of each millimeter increment of endometrial thickness. However, when the EMT ranged from 12-15 mm, were stable at the ideal level, that were not significantly associated with EMT growth. Additionally, clinical pregnancy rate and live birth rate were slightly reduced by 6% and 4% when EMT was ≥15mm. Meanwhile, the miscarriage rate was significantly declined by 8% (OR:0.92; 95%CI: 0.90-0.95)with each millimeter increment of EMT. And when EMT was thicker than 12mm, the miscarriage rate didn't change any more significantly.

CONCLUSIONS

Endometrial thickness exhibits a curvilinear relationship with pregnancy outcomes in fresh embryo transfer cycles. Clinical pregnancy rate, live birth rate and miscarriage rate may achieve their optimal level when EMT ≥ 12 mm, but some adverse pregnancy outcomes would be observed when EMT ≥15 mm especially for clinical pregnancy.