Comparing pregnancy outcomes between natural cycles and artificial cycles following frozen-thaw embryo transfers

Comparable ongoing pregnancy and pregnancy loss rates in natural cycle and artificial cycle frozen embryo transfers with intensive method-specific luteal phase support; a retrospective cohort study

STUDY OBJECTIVE

The absence of corpus lutea in artificial cycle (AC) frozen embryo transfers (FET) may increase the chances of pregnancy loss. In this retrospective cohort study, the efficacy of AC endometrial preparation was compared natural cycle (NC) endometrial preparation in terms of ongoing pregnancy.

METHODS

One thousand six hundred and eighteen consecutive vitrified-warmed blastocyst FET performed between December 2021 and November 2022 were included, with 1023 compared after exclusions according to the endometrial preparation method; 293 NC-FET, 143 modified NC-FET, 204 unprogrammed AC-FET, and 383 oral contraceptive pill (OCP) programmed AC-FET. Intensive method-specific luteal phase support (LPS) was administered in NC- (human chorionic gonadotropin and micronized vaginal progesterone), mNC- (micronized vaginal progesterone), and in AC-FET (micronized vaginal progesterone, intramuscular progesterone, and oral dydrogesterone).

RESULTS

Clinician choice of endometrial preparation method resulted in the NC- or AC-FET groups having distinct differences, with female age, antral follicle count and body mass index as well as the percentage of DOR or PCOS diagnosed patients significantly different. The unadjusted ongoing pregnancy and total pregnancy loss rates for NC-, mNC-, AC-, and ocp-AC-FET were 61.8 %, 55.2 %, 57.4 %, and 58.5 %, and 19.2 %, 24.0 %, 23.5 % and 23.8 %, respectively. In multivariate logistic regressions to predict the dependent outcomes of ongoing pregnancy and total pregnancy loss, none of the FET methods were selected as independent predictors.

CONCLUSION

Patients undergoing NC- and AC-FET with method-specific progesterone LPS had comparable ongoing pregnancy rates as well as total pregnancy loss rates, with NC-FET ranked first in the regression analysis.

Influencing factors and predictive model of live birth involving low-grade blastocyst frozen-thawed transfer: a retrospective study

BACKGROUND

Whether only low-grade blastocysts should undergo freeze-thaw transfer during the in vitro fertilization/intracytoplasmic sperm injection cycle remains controversial; however, high-quality embryos cannot be obtained from some patients. Therefore, we aimed to identify factors that may affect the live birth.

METHODS

A total of 662 couples with only low-grade blastocysts who voluntarily accepted freeze-thaw blastocyst transfer at a single reproductive center over a 7-year period were followed-up. According to the outcome after transfer, they were divided into live birth group and failed pregnancy group. A nomogram was constructed for predicting live births.

RESULTS

Baseline information and clinical treatment characteristics of patients in the two groups were comparable. Fifty-two of the 662 cycles (7.9%) resulted in live birth. Paternal age, maternal basal luteinizing hormone level, endometrial preparation scheme, and blastocyst development days were independent factors that affected low-grade blastocyst freeze-thaw transfer outcomes. The predictive model constructed based on these four factors presented favorable calibration and discriminatory abilities (area under the curve, 0.734; 95% confidence interval, 0.781-0.813).

CONCLUSIONS

For patients who exclusively underwent low-grade blastocyst freeze-thaw transfer, advanced paternal age and a high level of maternal basal luteinizing hormone adversely affected low-grade blastocyst freeze-thaw transfer outcomes. Artificial cycle preparation of the endometrium and day 5 blastocyst selection may improve the probability of live birth.

Treatment outcomes of blastocysts thaw cycles, comparing the presence and absence of a corpus luteum: a systematic review and meta-analysis

PURPOSE

This study aims to review the literature and perform a meta-analysis to determine if the presence of a corpus luteum has an impact on treatment outcomes in thaw cycles, where blastocyst embryos are transferred.

METHOD

PUBMED, EMBASE, CENTRAL and CINAHL were searched for papers published between January 2017 and 27 July 2020. Additional articles were selected from the reference list of the results and previous reviews. Three reviewers independently reviewed and extracted data. The meta-analysis was conducted though RevMan V.5.4.1. Studies were quality assessed with the Cochrane risk of bias tool and the Newcastle-Ottawa Scale.

RESULTS

Nine publications were included for data extraction and subsequent meta-analysis. Two studies were randomised controlled trials, and seven were cohort studies. Subgroup analysis of the different study designs was performed. While the rates of positive human chorionic gonadotropin results (relative risk, RR 1.0, 95% CI 0.95 to 1.05) and clinical pregnancies (RR 1.06, 95% CI 0.96 to 1.18) were comparable between the two groups, the rates of live births were higher in thaw cycles with a corpus luteum (RR 1.14, 95% CI 1.06 to 1.22). Analysis of pregnancy losses demonstrated that both biochemical pregnancy (early miscarriage) (RR 0.71, 95% CI 0.62 to 0.82) and miscarriages (RR 0.72, 95% CI 0.62 to 0.83) were increased in cycles without a corpus luteum.

CONCLUSION

Where clinically appropriate, the use of cycle types that have a functional corpus luteum should be favoured. There were several limitations to this study, including the quality of studies and the inherent bias of retrospective cohort studies. Further, high-quality research, particularly randomised controlled trials with blastocysts embryos, is required to further explore these findings.

PROSPERO REGISTRATION NUMBER

CRD42020209583.

Endometrial preparation methods prior to frozen embryo transfer: A retrospective cohort study comparing true natural cycle, modified natural cycle and artificial cycle

Purpose

The aim of this study was to compare the outcomes of three endometrial preparation methods prior to frozen embryo transfer (FET): Natural cycle (NC), modified natural cycle (mNC), and programmed/artificial cycle (AC) protocols. Primary outcomes investigated were clinical pregnancy rate (CPR) and live birth rate (LBR).

Methods

A retrospective study on 2080 FET cycles including patients ≤ 35 years with a BMI ≤ 30 who underwent FET with a single autologous blastocyst stage embryo at Aarhus University Hospital or Horsens Regional Hospital in the period 2013–2019. Only blastocysts frozen by vitrification were included. No luteal phase support (LPS) was used in natural cycles.

Results

In NC, mNC and AC, CPRs were 34.9%, 40.6% and 32.0%, while LBRs were 32.3%, 36.3% and 26.6%, respectively. There were no significant differences in main outcomes when comparing AC with NC [LBR: OR = 0.9 (0.6; 1.2), p = 0.4]. Compared to NC, mNC-FET displayed significantly higher positive hCG, implantation rate, CPR and LBR [LBR: OR = 1.4 (1.0; 1.9), p = 0.03]. An analysis with mNC as reference group demonstrated significantly better outcomes in the mNC group compared to AC [LBR: OR 0.6 (0.5; 0.8), p =  < 0.01].

Conclusion

The present study overall demonstrated better outcomes including LBR with mNC protocol as compared to NC and AC protocol, while comparison of AC and NC showed both protocols to be equally effective. A programmed cycle may be necessary for women with anovulatory cycles; however, normo-ovulating women may be offered a natural cycle protocol.

Trial registration number

3-3013-3047/1 and 31-1522-44. Date of registration: June 24, 2019 and April 23, 2020.

Impact of frozen thawed embryo transfer in hormone substituted cycles on thrombotic risk markers

INTRODUCTION

Fertility treatment with frozen thawed embryo transfer (FET) is widely used. Women treated in artificial cycles (AC-FET) receive high doses of estrogen in contrast to natural cycles (NC-FET), where no estrogen is administered. Estrogen substitution may be associated with increased risk of thromboembolism. Our aim is therefore to characterize changes in blood coagulation parameters defined as surrogate thrombotic risk markers in women undergoing estrogen substitution during AC-FET.

MATERIALS

In our prospective cohort study, we enrolled 34 women in either: AC-FET (n = 19) or NC-FET (n = 15). Women were recruited at the Department of Obstetrics and Gynaecology, Horsens Fertility Clinic, Denmark, from August 2019 - November 2020. Blood samples were obtained at four timepoints. Thrombin generation, platelet aggregation and fibrinolysis were evaluated as thrombotic risk markers.

RESULTS

Within the AC-FET group, we found a significantly shorter lagtime (p < 0.05) and time to peak (TTP) (p < 0.001) after hormone substitution compared to baseline. Furthermore, a significantly higher mean peak (p < 0.0001) and larger endogenous thrombin potential (ETP) (p < 0.0001) was observed. When compared to the NC-FET group, women receiving AC-FET had a significantly shorter mean TTP (p < 0.005), higher mean peak (p < 0.0001) and larger ETP (p < 0.05). Additionally, we demonstrated a significantly prolonged lysis time within the AC-FET group (p < 0.001).

CONCLUSION

Our results indicate that women receiving AC-FET have a significantly increased thrombin generation which may increase the thromboembolic risk in women being estrogen substituted.