Endocrine and biological factors influencing implantation of human embryos following cryopreservation

The effects of different endometrial preparation regimens on pregnancy outcomes in frozen-thawed embryo transfer cycles: a prospective randomized controlled study

OBJECTIVE

An increasing number of research have emerged to compare the pregnancy outcomes between the natural cycle and the hormone replacement therapy (HRT) cycle in preparing the endometrium for frozen-thawed embryo transfer (FET), but the results are controversial. This prospective randomized controlled study was hence designed to obtain more solid evidence.

MATERIALS AND METHODS

In this study, patients with regular menstrual cycle length (21-35 days) who underwent FET between January 2010 to December 2017 were recruited for this study. Upon further filtering with the selection criteria of patients being, a total of 405 patients were recruited and randomized. Finally, analysis was performed on 384 patients: 178 belonged to the natural cycle group whereas the remaining 206 were in the HRT group. The primary outcome was live birth rate, while the secondary outcomes were implantation rate, clinical pregnancy rate, early miscarriage rate, late miscarriage rate, multiple birth rate and low birth weight rate.

RESULTS

The live birth rate (37.6% vs 30.1%, p = 0.119) of natural cycle group were higher than those of the hormone replacement therapy group, although the difference was not significant. The secondary outcomes were not found to differ significantly between the two groups. Nonetheless, the endometrium was found to be thicker in the natural cycle group (10.75 mm) than the HRT group (9.00 mm) (p < 0.001).

CONCLUSION

No significant differences were observed between the pregnancy outcomes of the natural cycle group and the HRT group which comprised of patients with regular menstrual cycle length.

Higher live birth rate with stimulated rather than artificial cycle for frozen-thawed embryo transfer

OBJECTIVE

To study which endometrial preparation allows a better ongoing pregnancy rates (OPR) and live birth rate (LBR) after frozen-thawed embryo transfer (FET) between mild gonadotropin ovarian stimulation (OS) and artificial cycles (AC).

STUDY DESIGN

Retrospective follow-up study including all FET performed in one fertility center from 2013 to 2016. In the OS group, gonadotropins were followed by r-hCG triggering. Vaginal micronized progesterone (200 mg/day) was given systematically. In the AC group, estradiol (E2) was started on Day 1. Vaginal micronized progesterone (600 mg/d) was added to E2 for 12 weeks. Data were analyzed using a multiple regression model.

RESULTS

Among 1021 FETs, 35% underwent OS preparation, 65% had an AC. As expected, patients in the AC group suffered more from endometriosis (18.5% vs. 12.9%; p = .021) and polycystic ovarian syndrome (21.7% vs. 10.9%; p < .0001) than patients in the OS group. There was no difference between groups with respect to endometrial thickness, number of embryos transferred, development stage at FET, cryopreservation technique. Despite a similar clinical pregnancy rate (CPR) (24.4% vs. 20.8%; p = .189), the OPR was significantly higher in the OS than in the AC group (17.9% vs. 11%; p = .002), leading to an increased LBR (17.1% vs. 9.8%; p < .001). After adjusting for parameters usually linked to early pregnancy losses or potential bias (patient age at freezing, smoking status, PCOS, endometriosis, rank of transfer and previous miscarriages), the results remained significant.

CONCLUSION

Despite a similar CPR, LBR was significantly higher with mild OS than with the AC preparation, even after adjusting for potential confounders. In light of these results, the first-line endometrial preparation could be OS instead of an AC. In an AC, a potential defect of the luteal phase may exist, treatment could be optimized to avoid pregnancy losses. A randomized controlled trial should be undertaken to assess the role of OS and ACs in FET.

Cycle regimens for frozen-thawed embryo transfer

BACKGROUND

Among subfertile couples undergoing assisted reproductive technology (ART), pregnancy rates following frozen-thawed embryo transfer (FET) treatment cycles have historically been found to be lower than following embryo transfer undertaken two to five days following oocyte retrieval. Nevertheless, FET increases the cumulative pregnancy rate, reduces cost, is relatively simple to undertake and can be accomplished in a shorter time period than repeated in vitro fertilisation (IVF) or intracytoplasmic sperm injection (ICSI) cycles with fresh embryo transfer. FET is performed using different cycle regimens: spontaneous ovulatory (natural) cycles; cycles in which the endometrium is artificially prepared by oestrogen and progesterone hormones, commonly known as hormone therapy (HT) FET cycles; and cycles in which ovulation is induced by drugs (ovulation induction FET cycles). HT can be used with or without a gonadotrophin releasing hormone agonist (GnRHa). This is an update of a Cochrane review; the first version was published in 2008.

OBJECTIVES

To compare the effectiveness and safety of natural cycle FET, HT cycle FET and ovulation induction cycle FET, and compare subtypes of these regimens.

SEARCH METHODS

On 13 December 2016 we searched databases including Cochrane Gynaecology and Fertility's Specialised Register, CENTRAL, MEDLINE, Embase, PsycINFO and CINAHL. Other search sources were trials registers and reference lists of included studies.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) comparing the various cycle regimens and different methods used to prepare the endometrium during FET.

DATA COLLECTION AND ANALYSIS

We used standard methodological procedures recommended by Cochrane. Our primary outcomes were live birth rates and miscarriage.

MAIN RESULTS

We included 18 RCTs comparing different cycle regimens for FET in 3815 women. The quality of the evidence was low or very low. The main limitations were failure to report important clinical outcomes, poor reporting of study methods and imprecision due to low event rates. We found no data specific to non-ovulatory women. 1. Natural cycle FET comparisons Natural cycle FET versus HT FETNo study reported live birth rates, miscarriage or ongoing pregnancy.There was no evidence of a difference in multiple pregnancy rates between women in natural cycles and those in HT FET cycle (odds ratio (OR) 2.48, 95% confidence interval (CI) 0.09 to 68.14, 1 RCT, n = 21, very low-quality evidence). Natural cycle FET versus HT plus GnRHa suppressionThere was no evidence of a difference in rates of live birth (OR 0.77, 95% CI 0.39 to 1.53, 1 RCT, n = 159, low-quality evidence) or multiple pregnancy (OR 0.58, 95% CI 0.13 to 2.50, 1 RCT, n = 159, low-quality evidence) between women who had natural cycle FET and those who had HT FET cycles with GnRHa suppression. No study reported miscarriage or ongoing pregnancy. Natural cycle FET versus modified natural cycle FET (human chorionic gonadotrophin (HCG) trigger)There was no evidence of a difference in rates of live birth (OR 0.55, 95% CI 0.16 to 1.93, 1 RCT, n = 60, very low-quality evidence) or miscarriage (OR 0.20, 95% CI 0.01 to 4.13, 1 RCT, n = 168, very low-quality evidence) between women in natural cycles and women in natural cycles with HCG trigger. However, very low-quality evidence suggested that women in natural cycles (without HCG trigger) may have higher ongoing pregnancy rates (OR 2.44, 95% CI 1.03 to 5.76, 1 RCT, n = 168). There were no data on multiple pregnancy. 2. Modified natural cycle FET comparisons Modified natural cycle FET (HCG trigger) versus HT FETThere was no evidence of a difference in rates of live birth (OR 1.34, 95% CI 0.88 to 2.05, 1 RCT, n = 959, low-quality evidence) or ongoing pregnancy (OR 1.21, 95% CI 0.80 to 1.83, 1 RCT, n = 959, low-quality evidence) between women in modified natural cycles and those who received HT. There were no data on miscarriage or multiple pregnancy. Modified natural cycle FET (HCG trigger) versus HT plus GnRHa suppressionThere was no evidence of a difference between the two groups in rates of live birth (OR 1.11, 95% CI 0.66 to 1.87, 1 RCT, n = 236, low-quality evidence) or miscarriage (OR 0.74, 95% CI 0.25 to 2.19, 1 RCT, n = 236, low-quality evidence) rates. There were no data on ongoing pregnancy or multiple pregnancy. 3. HT FET comparisons HT FET versus HT plus GnRHa suppressionHT alone was associated with a lower live birth rate than HT with GnRHa suppression (OR 0.10, 95% CI 0.04 to 0.30, 1 RCT, n = 75, low-quality evidence). There was no evidence of a difference between the groups in either miscarriage (OR 0.64, 95% CI 0.37 to 1.12, 6 RCTs, n = 991, I² = 0%, low-quality evidence) or ongoing pregnancy (OR 1.72, 95% CI 0.61 to 4.85, 1 RCT, n = 106, very low-quality evidence).There were no data on multiple pregnancy. 4. Comparison of subtypes of ovulation induction FET Human menopausal gonadotrophin(HMG) versus clomiphene plus HMG HMG alone was associated with a higher live birth rate than clomiphene combined with HMG (OR 2.49, 95% CI 1.07 to 5.80, 1 RCT, n = 209, very low-quality evidence). There was no evidence of a difference between the groups in either miscarriage (OR 1.33, 95% CI 0.35 to 5.09,1 RCT, n = 209, very low-quality evidence) or multiple pregnancy (OR 1.41, 95% CI 0.31 to 6.48, 1 RCT, n = 209, very low-quality evidence).There were no data on ongoing pregnancy.

AUTHORS' CONCLUSIONS

This review did not find sufficient evidence to support the use of one cycle regimen in preference to another in preparation for FET in subfertile women with regular ovulatory cycles. The most common modalities for FET are natural cycle with or without HCG trigger or endometrial preparation with HT, with or without GnRHa suppression. We identified only four direct comparisons of these two modalities and there was insufficient evidence to support the use of either one in preference to the other.

GnRh Agonist Treatment Improves Implantation and Pregnancy Rates of Frozen-Thawed Embryos Transfer

OBJECTIVE

To study the effect of GnRh agonist administration prior to estrogen-progesterone preparation of the endometrium on the implantation rate in frozen-thawed embryo transfer (FET) cycles in infertile patients treated with IVF/ICSI.

DESIGN

Prospective controlled study.

SETTING

Private center in Alexandria, Egypt.

PATIENTS

Patients undergoing frozen-thawed embryo transfer FET.

INTERVENTIONS

Patients were divided into two groups, A and B. Group A patients consisted of 110 patients (110 cycles) who received daily subcutaneous injections of 0.1 mg of the GnRh agonist triptorelin starting from the mid-luteal phase of the cycle preceding the actual FET cycle. The dose was reduced to 0.05 mg from the second day of the cycle when daily oral estradiol valerate 6 mg was also started. Daily vaginal supplementation of micronized progesterone 400 mg b.d. was started after 12 days when the GnRh agonist was also stopped. Frozen-thawed embryos were transferred on day + 1 of their chronological age and when the endometrium reached 12 mm in thickness. Group B consisted of 100 patients (100 cycles) who started daily estradiol valerate 6 mg administration from the second day of the FET cycle and followed the same regimen but without prior treatment with triptorelin.

MAIN OUTCOME MEASURES

Implantation and pregnancy rates were compared among the two groups.

RESULTS

There was a significant increase in implantation rate in the GnRh agonist group (group A) compared to the estrogen and progesterone only group (group B) (44.1 vs. 21.1 %; P = 0.002*). The pregnancy rate was also significantly higher in group A compared to group B (65.5 vs. 42 %, P = 0.013*).

CONCLUSIONS

GnRh agonist administration during endometrial preparation for FET increases the implantation and pregnancy rates.

Preparation of endometrium for frozen embryo replacement cycles: a systematic review and meta-analysis

PURPOSE

The purpose of this study was to evaluate the best protocol to prepare endometrium for frozen embryo replacement (FER) cycles.

METHODS

This study is a systematic review and meta-analysis. Following PubMed and OvidSP search, a total of 1166 studies published after 1990 were identified following removal of duplicates. Following exclusion of studies not matching our inclusion criteria, a total of 33 studies were analyzed. Primary outcome measure was live birth. The following protocols, including true natural cycle (tNC), modified natural cycle (mNC), artificial cycle (AC) with or without suppression, and mild ovarian stimulation (OS) with gonadotropin (Gn) or aromatase inhibitor (AI), were compared.

RESULTS

No statistically significant difference for both clinical pregnancy and live birth was noted between tNC and mNC groups. When tNC and AC without suppression groups are compared, there was a statistically significant difference in clinical pregnancy rate in favor of tNC, whereas it failed to reach statistical significance for live birth. When tNC and AC with suppression groups are compared, there was a statistically significant difference in live birth rate favoring the latter. Similar pregnancy outcome was noted among mNC versus AC with or without suppression groups. Similarly, no difference in clinical pregnancy and live birth was noted when ACs with or without suppression groups are compared.

CONCLUSIONS

There is no consistent superiority of any endometrial preparation for FER. However, mNC has several advantages (being patient-friendly; yielding at least equivalent or better pregnancy rates when compared with tNC and AC with or without suppression; may not require LPS). Mild OS with Gn or AI may be promising.

Frozen-thawed embryo transfer in a natural or mildly hormonally stimulated cycle in women with regular ovulatory cycles: a RCT

STUDY QUESTION

Can ovarian stimulation with low dose hMG improve the implantation rate (IR) per frozen-thawed embryo transferred (FET) when compared with natural cycle in an FET programme in women with a regular ovulatory cycle?

SUMMARY ANSWER

Both IR and live birth rate (LBR) per FET were similar in the group with mild ovarian stimulation and the natural cycle group.

WHAT IS KNOWN ALREADY

Different cycle regimens for endometrial preparation are used prior to FET: spontaneous ovulatory cycles, cycles with artificial endometrial preparation using estrogen and progesterone hormones, and cycles stimulated with gonadotrophins or clomiphene citrate. At present, it is not clear which regimen results in the highest IR or LBR. More specifically, there are no RCTs in ovulatory women comparing reproductive outcome after FET during a natural cycle and during a hormonally stimulated cycle.

STUDY DESIGN, SIZE, DURATION

A total of 410 women scheduled for FET during 579 cycles (December 2003-September 2013) were enrolled in an open-label RCT to natural cycle (NC FET group, n = 291) or to a cycle hormonally stimulated with s.c. gonadotrophins (hMG FET group, 37.5-75 IU per day, n = 288). A total of 672 embryos were transferred during 434 cycles (332 embryos and 213 cycles in the NC FET group; 340 embryos and 221 cycles in the hMG FET group). Assuming a = 0.05 and 80% power, it was calculated that 219 frozen-thawed embryos were required for transfer in each group to demonstrate a difference of 10% in IR.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Women were eligible according to the following inclusion criteria: regular ovulatory cycle, female age ≥21 years and ≤45 years, informed consent. FET cycles with preimplantation genetic screening were excluded. The primary outcome was IR per embryo transferred. Secondary outcomes included IR with fetal heart beat (FHB), LBR per embryo transferred and endometrial thickness on the day of hCG administration. Statistical analysis was by intention to treat and controlled for the presence of multiple measures, as eligible women could be randomized in more than one cycle. Chi-square and independent t-test were used to compare categorical and continuous variables. The relative risk (RR) was estimated using a Poisson model with log link. Hierarchical models with random intercepts for patient and cycle were considered to account for clustering of cycles within patients and of embryos within cycles.

MAIN RESULTS AND THE ROLE OF CHANCE

The primary outcome, IR per embryo transferred, was not statistically different between the NC FET group (41/332 (12.35%)) and in the hMG FET group (55/340 (16.18%)) (RR 1.3 (95% confidence interval (CI) 0.9-2.0), P = 0.19). Similarly, the secondary outcome, IR with FHB per embryo transferred, was 34/332 (10.24%) in the NC FET group and 48/340 (14.12%) in the hMG FET group (RR 1.4 (95% CI 0.9-2.1), P = 0.15). The LBR per embryo transferred was 32/332 (9.64%) in the NC FET group and 45/340 (13.24%) in the hMG FET group (RR 1.4 (95% CI 0.9-2.2), P = 0.17). Endometrial thickness was also similar in both groups [8.9 (95% CI 8.7-9.1) in the NC FET group and 8.9 (95% CI 8.7-9.1) in the hMG FET group]. The duration of the follicular phase was significantly shorter (P < 0.001) in the hMG FET group [13.7 days (95% CI 13.2-14.2)] than in the NC FET group [15.4 days (95% CI 14.8-15.9)].

LIMITATIONS, REASONS FOR CAUTION

Randomization of cycles instead of patients; open-label design; relatively long period of recruitment.

WIDER IMPLICATIONS OF THE FINDINGS

Our observation that the IR per embryo transferred is not significantly increased after FET during natural or gonadotrophin stimulated cycle, suggests that the effect of mild hormonal stimulation with gonadotrophins is smaller than what was considered clinically relevant with respect to reproductive outcome after FET. These data suggest that endometrial receptivity is not relevantly improved, but also not impaired after hormonal stimulation with gonadotrophins. Since FET during a natural cycle is cheaper and more patient-friendly, we recommend this regimen as the treatment of choice for women with regular cycles undergoing FET.

TRIAL REGISTRATION NUMBER

clinicaltrials.gov NCT00492934.

TRIAL REGISTRATION DATE

26 June 2007.

DATE OF FIRST PATIENT'S ENROLMENT

1 December 2003.

Patients undergoing frozen-thawed embryo transfer have similar live birth rates in spontaneous and artificial cycles

PURPOSE

To evaluate the outcome of frozen-thawed embryo transfer (FET) when freezing takes place at the pronuclear stage, a retrospective analysis was performed comparing spontaneous and artificial cycles.

METHODS

148 women received FET in a spontaneous cycle (Group A) and 55 women received FET in an artificial cycle (Group B) induced by administering estrogen (E2) and progesterone (P). Pregnancy rates, endometrial thickness and serum levels of E2, P and luteinizing hormone (LH) were measured. Statistical analysis included the mean, the standard deviation, the Chi-squared test and the T-test.

RESULTS

The clinical pregnancy rate was 34.5% for Group A and 21.8% for Group B (p = 0.084), with a live birth rate of 20.9% and 12.7% respectively (p = 0.15). There was no difference in endometrial thickness or the P levels, while LH and E2 levels were significantly higher in group B (p < 0.0001).

CONCLUSION

Our retrospective study shows a trend towards higher pregnancy rates and live birth rates with the administration of FET during a spontaneous cycle compared to FET during an artificial cycle. Large randomized controlled trials are needed to confirm this trend.

Does a vitrified blastocyst stage embryo transfer program need hormonal priming for endometrial preparation?

AIM

To compare the clinical outcomes of a vitrified blastocyst stage embryo transfer (ET) program among natural, ovulation induced and artificial cycles.

MATERIAL & METHODS

The clinical outcomes were retrospectively analyzed in three groups according to endometrial preparation (natural cycle group [n = 34], ovulation induced [n = 21], and artificial cycles [n = 70]) among women that underwent vitrified blastocyst stage ET.

RESULTS

The overall pregnancy rate was 48.8%. There were no significant differences in the duration of endometrial preparation, endometrial thickness on the day of progesterone or human chorionic gonadotropin administration, implantation and clinical pregnancy rates among the three groups. Triple-line endometrial patterns were more frequently observed in the natural and ovulation induced groups than in the artificial cycle group (85.3% vs 64.3%, P = 0.021; 90.5% vs 64.3%, P = 0.016).

CONCLUSION

Our findings suggest that the types of endometrial preparation may have no significant effect on the clinical outcomes of vitrified blastocyst ET. Hormonal priming does not appear to be a prerequisite for endometrial preparation for vitrified blastocyst ET.

Cycle regimens for frozen-thawed embryo transfer

BACKGROUND

Pregnancy rates following frozen-thawed embryo transfer (FET) treatment have always been found to be lower than following embryo transfer using fresh embryos. Nevertheless, FET increases the (cumulative) pregnancy rate, reduces cost, is relatively simple to undertake and can be accomplished in a shorter time period compared to repeated 'fresh' cycles. FET is performed using different cycle regimens: spontaneous ovulatory cycles, cycles in which ovulation is induced by drugs and cycles in which the endometrium is artificially prepared by oestrogen (O) and progesterone (P) hormones, with or without a gonadotrophin releasing hormone agonist (GnRHa).

OBJECTIVES

To determine whether there is a difference in outcome between natural cycle FET, artificial cycle FET and ovulation induction cycle FET.

SEARCH STRATEGY

Our search included CENTRAL,DARE, MEDLINE (1950 to 2007), EMBASE (1980 to 2007) and CINAHL (1982 to 2007).

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing the various cycle regimens and different methods used to prepare the endometrium during FET in assisted reproductive technology (ART).

DATA COLLECTION AND ANALYSIS

The two authors independently extracted data. Dichotomous outcomes results (e.g. clinical pregnancy rate) were expressed as an odds ratio (OR) with 95% confidence intervals (CI) for each study. Continuous outcome results (endometrial thickness) were expressed as weighted mean difference (WMD). Where suitable, results were combined for meta-analysis with RevMan software using the Peto-modified Mantel-Haenszel method.

MAIN RESULTS

Seven randomised controlled studies assessing six comparisons and including 1120 women in total were included in this review.1) O + P FET versus natural cycle FET: this comparison demonstrated no significant differences in outcomes but confidence intervals remain wide, and therefore moderate differences in either direction remain possible (OR 1.06, 95% CI 0.40 to 2.80, P 0.91).2) GnRHa + O + P FET versus O + P FET: this comparison showed that the live birth rate per woman was significantly higher in the former group (OR 0.38, 95% CI 0.17 to 0.84, P 0.02). The clinical pregnancy rate was also higher but not significantly so (OR 0.76, 95% CI 0.52 to 1.10, P 0.14).3) O + P FET versus follicle stimulating hormone (FSH) FET, 4) O + P FET versus clomiphene FET and 5) GnRHa + O + P FET versus clomiphene FET: there were no differences in the outcomes in the comparison of these cycle regimens.6) Clomiphene + human menopausal gonadotrophin (HMG) FET versus HMG FET: in a comparison of two ovulation induction regimes the pregnancy rate was found to be significantly higher in the HMG group (OR 0.46, 95% CI 0.23 to 0.92). There were also fewer cycle cancellations and a lower multiple pregnancy rate when HMG was used without clomiphene but these did not reach statistical significance.

AUTHORS' CONCLUSIONS

At the present time there is insufficient evidence to support the use of one intervention in preference to another.

New challenges in human in vitro fertilization

This review assesses some scientific and ethical problems with human in vitro fertilization. Improved selection of viable embryos, better culture conditions, and greater understanding of the uterine environment will increase success and prevent multiple pregnancy. Further advances will also improve oocyte cryopreservation, in vitro maturation of oocytes, knowledge of sperm function, and sperm microinjection. Preimplantation diagnosis will help avoid genetic diseases and increase understanding of embryonic defects and the viability of zygotes. The greatest ethical problem with all these developments seems to be delivery of these complex treatments when health-care resources are increasingly limited.