A randomized controlled trial of a soft double lumen embryo transfer catheter versus a firm single lumen catheter: significant improvements in pregnancy rates

Interventions to optimize embryo transfer in women undergoing assisted conception: a comprehensive systematic review and meta-analyses

BACKGROUND

Several interventions and techniques are suggested to improve the outcome of embryo transfer (ET) in assisted conception. However, there remains no consensus on the optimal practice, with high variations among fertility specialists.

OBJECTIVE AND RATIONALE

We conducted a comprehensive systematic review and meta-analyses of randomized controlled trials (RCTs) aiming to identify effective interventions that could be introduced around the time of ET to improve reproductive outcomes.

SEARCH METHODS

We searched the electronic databases (MEDLINE, EMBASE and Cochrane CENTRAL) from inception until March 2021 using a multi-stage search strategy of MeSH terms and keywords, and included all RCTs that evaluated an intervention in the 24-h period before/after ET in women undergoing IVF/ICSI. Our primary outcome was clinical pregnancy rate post-ET confirmed as viable pregnancy on ultrasound scan. We assessed the risk of bias in included trials and extracted data in duplicate. We pooled data using a random-effect meta-analysis and reported using risk ratio (RR) with 95% CI. We explored publication bias and effect modifiers using subgroup analyses.

OUTCOMES

Our search yielded 3685 citations of which we included 188 RCTs (38 interventions, 59 530 participants) with a median sample size of 200 (range 26-1761). The quality of included RCTs was moderate with most showing a low risk of bias for randomization (118/188, 62.8%) and attrition (105/188, 55.8%) but there was a significant risk of publication bias (Egger's test P = 0.001). Performing ET with ultrasound guidance versus clinical touch (n = 24, RR 1.265, 95% CI 1.151-1.391, I2 = 38.53%), hyaluronic acid versus routine care (n = 9, RR 1.457, 95% CI 1.197-1.261, I2 = 46.48%) and the use of a soft versus hard catheter (n = 27, RR 1.122, 95% CI 1.028-1.224, I2 = 57.66%) led to higher clinical pregnancy rates. Other pharmacological add-ons also showed a beneficial effect including granulocyte colony-stimulating factor (G-CSF: n = 4, RR 1.774, 95% CI 1.252-2.512, I2 = 0), Atosiban (n = 7, RR 1.493, 95% CI 1.184-1.882, I2 = 68.27%) and hCG (n = 17, RR 1.232, 95% CI 1.099-1.382, I2 = 57.76%). Bed rest following ET was associated with a reduction in clinical pregnancy (n = 6, RR 0.857, 95% CI 0.741-0.991, I2 = 0.01%). Other commonly used interventions, such as non-steroidal anti-inflammatory drugs, prophylactic antibiotics, acupuncture and cervical mucus removal, did not show a significant benefit on reproductive outcomes. Our effect estimates for other important outcomes, including miscarriage and live birth, were limited by the varied reporting across included RCTs.

WIDER IMPLICATIONS

Using ultrasound guidance, soft catheters and hyaluronic acid at the time of ET appears to increase clinical pregnancy rates. The use of Atosiban, G-CSF and hCG showed a trend towards increased clinical pregnancy rate, but larger trials are required before adopting these interventions in clinical practice. Bed rest post-ET was associated with a reduction in clinical pregnancy and should not be recommended.

Evaluation of a strategy for difficult embryo transfers from a prospective series of 2,046 transfers

Objective

To evaluate an embryo transfer strategy for difficult transfers (DiTs).

Design

Prospective, nonrandomized, observational, cohort study

Setting

A hospital fertility center in France.

Patient(s)

Data were collected on all embryo transfers conducted using the strategy between February 2014 and February 2020.

Intervention(s)

Anatomical characteristics that could cause DiT were identified by transvaginal ultrasound and the catheter was adapted accordingly. Transfer was guided by transvaginal ultrasound. After passage through the cervix, a rest period was introduced to allow any contractions to stop before embryo deposition in the uterus.

Main Outcome Measure(s)

The primary criterion was the percentage of pregnancies per transfer (P/T) after an easy transfer (EaT) or a DiT. The secondary criteria included the anatomical causes of DiT and the patients’ levels of discomfort.

Result(s)

Of 2,046 transfers, 257 (12%) were DiTs: minor difficulties (n = 152; 7.4%), major difficulties (n = 96; 4.7%), very significant difficulties (n = 7; 0.3%), or impossible (n = 2; 0.1%). The most common causes of DiTs were endocervical crypts (54%), tortuous cervical canal (36%), and marked uterine anteversions (30%). Several causes were often responsible for DiTs. There was no statistically significant difference in the P/T between the EaTs (n = 1,789, 41%) and all degrees of DiT (n = 257, 37%). In addition, there was no statistically significant difference between the level of patient-reported discomfort in the EaT and DiT groups.

Conclusion(s)

This study demonstrated that an adapted embryo transfer strategy, monitored by transvaginal ultrasound, led to similar pregnancy rates regardless of whether the transfer was easy or difficult.

National Survey Highlights the Urgent Need for Standardisation of Embryo Transfer Techniques in the UK

Embryo transfer (ET) is one of the vital steps in the in vitro fertilisation (IVF) process, yet there is wide variation in ET technique throughout the UK, without a nationally approved standardised approach. The aim of this study was to gain contemporaneous information regarding the current clinical ET practice in the UK. Method: A 38-question electronic survey was distributed to the 79 UK Human Fertilisation and Embryology Authority (HFEA) registered clinics performing ETs. Results: In total, 59% (47/79) of units responded, 83% (39/47) performing ultrasound-guided transfers, with 42% (20/47) of units using a tenaculum; 22% (10/45) would proceed with transfer regardless of fluid in the endometrial cavity. In 91% (43/47) of units, embryos were deposited in the upper/middle portion of the uterine cavity, but interpretation of this area ranged from 0.5 to >2 cm from the fundus, with 68% (32/47) allowing patients to mobilise immediately after transfer. In 60% (27/45) of clinics, success rates were based on clinical pregnancy rates (CPR). Conclusion: Within the UK there is a wide range of variability in ET techniques, with >70% of discordance in survey-responses between clinics. Whilst there are areas of good practice, some disadvantageous techniques continue to persist. This survey emphasises the importance of developing a standardised, evidence-based approach to improve ET success rates.

Embryo transfer techniques

Embryo transfer is the final and rate-limiting step of the assisted reproductive technique. Few advances have occurred in the last few decades with regard to this procedure. Studies conducted thus far have focused on factors and interventions taking place before, during and after this procedure. These factors are highly varied and range from methods to improve the psychological state of the patients to methods aimed at reducing uterine contractility and methods aimed at optimising the precise transfer of the embryo. The key question is which factors and interventions have thus far been proven to increase pregnancy rates and live birth rates. This paper aims to review the evidence relating to embryo transfer techniques in a systematic manner with a view to provide practical recommendations to practitioners involved in the procedure.

Quality Management Issues in the Assisted Reproduction Laboratory

In the United States, the Clinical Laboratory Improvement Act (CLIA) of 1988 describes requirements and guidelines for implementing a quality control/quality assurance (QC/QA) program for moderate and high complexity laboratories. These requirements and guidelines apply to Assisted Reproductive Technology (ART) laboratories as well. The general topic of QC and QA as it pertains to in vitro fertilization (IVF) and embryo transfer (ET) is extensively reviewed. This review summarizes many of the QC and QA events that contribute to the advancement of knowledge in this biotechnological field. These events include control of the culture environment inside and outside of the incubator, as well as factors that affect culture media. This review also discusses, in considerable detail, the QC and the QA that pertain to equipment used within the laboratory and how to control for potential contaminants, which reside within the laboratory. This review provides evidence to indicate the need for laboratory personnel to monitor quality improvement issues on a continuous basis. Personnel must be willing to change as improvements in technology occur in order to meet the ever-evolving demands of a more difficult patient population. Suggestions for meeting these demands are offered.

Techniques for preparation prior to embryo transfer

BACKGROUND

Embryo transfer (ET) is the final and most vulnerable step in in vitro fertilisation (IVF) treatment. Pregnancy rates after ET may be influenced by several factors including cervical preparation, the performance of a dummy or mock transfer, the choice of catheter, the use of ultrasound guidance, removing the mucus or blood on the catheter, and straightening of the utero-cervical angle. Recent research has focused on improving the embryo transfer technique in the hope of increasing the success rates of IVF. This review focused on preparation techniques as it is unclear whether these simple interventions will make ET an easier procedure with higher success rates and lower complication rates.

OBJECTIVES

To determine whether different preparation techniques prior to ET result in improved IVF outcomes.

SEARCH STRATEGY

The Cochrane Menstrual Disorders and Subfertility Group Specialised Register, CENTRAL (The Cochrane Library), MEDLINE, EMBASE, CINAHL, and PsycINFO were searched (November 2008). The citation lists of relevant publications, reviews, and included studies were handsearched. Experts in the field were contacted to identify any unpublished trials.

SELECTION CRITERIA

Only truly randomised controlled trials of the interventions straightening the utero-cervical angle, dummy transfer prior to ET, cervical and endometrial preparation, and embryo afterloading were included. The primary outcomes were live birth rate and pregnancy rate per woman randomised. Participants were women with any type of subfertility undergoing IVF treatment and reaching the ET stage.

DATA COLLECTION AND ANALYSIS

Two review authors critically appraised potentially eligible studies. Ten studies were included in this review and data were independently extracted by two review authors. Disagreements were resolved by discussion and involvement of a third author. Risk of bias was also independently assessed by two authors. Dichotomous outcome data were expressed as Peto odds ratios. Subgroup analysis and the investigation of heterogeneity were planned.

MAIN RESULTS

At the time of ET, there was no evidence of benefit with the following interventions: full bladder, removal of cervical mucus, flushing the endocervical canal or the endometrial cavity. We did not identify any eligible studies for dummy transfer, changing patient position, the use of a tenaculum, or embryo afterloading.

AUTHORS' CONCLUSIONS

On the basis of the evidence in this review, no specific implications for practice are made. It is recommended, in general, that more, larger studies are done on ET preparation techniques. The studies need to be of a higher quality with better explained methods, more specified inclusion and exclusion criteria, and more participants.

Prospective randomized comparison of Wallace and Labotect embryo transfer catheters

The aim of this study was to compare the clinical performance of Wallace and Labotect embryo transfer catheters in a single assisted reproduction centre. A total of 260 women undergoing embryo transfer were randomized between Wallace and Labotect catheters. When both catheters failed to negotiate the cervical canal, the transfer was accomplished with a stiff catheter. Intention to treat analysis revealed that Wallace and Labotect embryo transfer catheters yielded statistically similar clinical pregnancy (44.6 versus 34.6%), implantation (23.2 versus 18.9%) and ongoing pregnancy (38.5 versus 27.7%) rates. As treated analysis revealed clinical pregnancy rates of 42.5 versus 35.4%, implantation rates of 22.3 versus 20.6% and ongoing pregnancy rates of 36.8 versus 28.3% with Wallace and Labotect catheters respectively. Catheter change due to unsuccessful negotiation of the internal cervical os was significantly more frequently necessary when embryo transfer was first intended with the Wallace than the Labotect catheter (P < 0.001; 33 and 2% respectively). Although not being statistically significant, the observed differences may be regarded as clinically important and may reach statistical significance in larger trials. More trials are necessary before reaching a definitive conclusion regarding the performance of the Labotect embryo transfer catheter.

Evidence of improving quality of reporting of randomized controlled trials in subfertility

BACKGROUND

The quality of randomized controlled trials (RCTs) in subfertility and their suitability for inclusion in meta-analyses have been assessed in the past and found to be insufficient. Our aim was to assess whether this quality has improved over time, particularly since the publication of the Consolidated Standards of Reporting Trials (CONSORT) statement, and to assess what proportion of trials could be included in the meta-analyses of pregnancy outcomes such as those included in Cochrane Reviews.

METHODS

A selection of subfertility trials published in 1990, 1996 and 2002 was collected from the Cochrane Menstrual Disorder and Subfertility Group (MDSG) database. Only trials published in English as full journal articles, claiming to be randomized and reporting on pregnancy outcomes, were included.

RESULTS

One hundred and sixty-four trials met our inclusion criteria. Twenty-four (15%) were found not to be randomized, despite claims, and only 10 trials (6%) provided adequate details on the methods of randomization and allocation concealment. Of these, only three had sufficient details extractable to allow for an intention-to-treat analysis of the outcome 'live birth'.

CONCLUSIONS

Although an improvement in some subfertility-specific issues was observed, the quality of reporting of RCTs still needs to improve to make them suitable for inclusion in meta-analyses such as those in the Cochrane Library.

Firm embryo transfer catheters for assisted reproduction: a systematic review and meta-analysis using direct and adjusted indirect comparisons

A systematic review of published evidence on firm embryo transfer catheters is presented. Extensive searches were conducted for full-text manuscripts, abstracts, ongoing and unpublished trials. Direct and adjusted indirect comparisons were undertaken, where appropriate. Twenty-six randomized controlled trials comparing embryo transfer catheters were identified. Only two trials (314 transfers) compared different firm embryo catheters. Using direct comparison, both the Tom Cat and Tefcat catheters demonstrated statistically significant increased chances of clinical pregnancy compared with the Tight Difficult Transfer (TDT) catheter (P=0.007; OR=3.67, 95% CI=1.48-9.10 and P<0.0001; OR=4.71, 95% CI=2.34-9.48 respectively). The implantation rates were also higher with the Tom Cat and Tefcat catheters than the TDT catheter (P=0.005; OR=3.67, 95% CI=1.48-9.10 and P<0.00001; OR=4.29, 95% CI=2.45-7.50 respectively). Using adjusted indirect comparison, Tom Cat and Tefcat catheters were compared, and shown to have similar pregnancy and implantation rates (OR=0.99; 95% CI=-0.87-1.79 and OR=0.86; 95% CI=-0.77-1.35). In conclusion, both Tom Cat and Tefcat catheters give better outcomes than the TDT catheter, but are similar to each other.

A review and meta-analysis of prospective trials comparing different catheters used for embryo transfer

OBJECTIVE

To determine the relative efficacy of different types of embryo transfer (ET) catheters.

DESIGN

Systematic review and meta-analysis of prospective randomized, controlled trials comparing at least two different ET catheters.

SETTING

Infertility centers providing treatment with in vitro fertilization/embryo transfer (IVF-ET).

PATIENT(S)

Women undergoing ET.

INTERVENTION(S)

Embryo transfer with soft or hard catheters.

MAIN OUTCOME MEASURE(S)

Clinical pregnancy rate.

RESULT(S)

A total of seven prospective trials were identified that compared soft (Cook or Wallace) catheters with hard (TDT, Frydman, Tomcat, Rocket) catheters. The meta-analysis demonstrated an increased chance of clinical pregnancy when soft ET catheters were used. The TDT catheter was compared against both soft catheters and other hard catheters, showing decreased chance of clinical pregnancy when the TDT catheter was used. Six more prospective trials were identified comparing the Cook and Wallace soft catheters, and the meta-analysis of these data showed no demonstrable difference in clinical pregnancy rates.

CONCLUSION(S)

An increased chance of clinical pregnancy is achieved when soft ET catheters are used. There appears to be little difference between the Cook and Wallace soft catheters.

Embryo transfer: factors involved in optimizing the success

PURPOSE OF REVIEW

Embryo transfer is arguably the most critical step in assisted reproduction. The purpose of this article is to review the different aspects of the procedure in the light of recent evidence.

RECENT FINDINGS

Randomized trials have shown that significantly higher pregnancy rates are obtained when embryo transfer is performed under ultrasound guidance, the embryos are deposited in the middle part of the uterine cavity, an atraumatic technique is used and when low-dose aspirin is routinely administered following the procedure. Blood in the catheter and leaving the embryos inside it for more than 120 s diminish the pregnancy rate significantly. Air in the catheter, immediate removal of the catheter, performing two transfers in the same cycle, prolonged bed rest, sexual intercourse after embryo transfer or the use of sildenafil do not affect the results. Based on currently available evidence, Cochrane reviews have concluded that the live birth rate is not increased by delaying embryo transfer from day two to three or to the blastocyst stage, and that single embryo transfer leads to lower live birth rates than the transfer of two embryos. The value of a mock transfer a few days before the actual procedure has been challenged as the position of the uterus may change. The effect of holding the cervix with a volsellum, routinely administering antibiotics and the superiority of one catheter over the others is still to be determined.

SUMMARY

Recent studies confirm the importance of the various aspects of embryo transfer. More randomized studies are needed to further evaluate them.

Modern embryo transfer catheters and pregnancy outcome: a prospective randomized trial

OBJECTIVE

Embryo transfer (ET) is the final crucial step in IVF treatment. The type of catheter used can affect the pregnancy rate (PR). In this prospective, randomized trial we compared the clinical PR between the Wallace and the Cook K-Jet embryo transfer catheters.

DESIGN

Prospective, randomized clinical trial.

SETTING

A National Health Service Assisted Reproduction Unit.

PATIENT(S)

One hundred fifty women undergoing a fresh ET. Age more than 40 years, a high basal FSH, a previous difficult ET, or more than six previous ETs were the exclusion criteria.

INTERVENTION(S)

Women undergoing a fresh ET were randomized at the time of ET to either the Cook K-Jet or Wallace embryo transfer catheter. The randomization was stratified according to age and the number of previous ETs.

MAIN OUTCOME MEASURE(S)

Clinical PR.

RESULT(S)

There was no significant difference in the clinical PR between the Wallace and the Cook catheters (22/75 [29.3%] and 23/75 [30.6%], relative risk [RR]: 0.96 [95% confidence interval 0.58-1.58]).

CONCLUSION(S)

There is no significant difference in the PRs achieved by modern, soft, double-lumen ET catheters.

Soft versus firm embryo transfer catheters for assisted reproduction: a systematic review and meta-analysis*

BACKGROUND

The true impact of the embryo transfer catheter choice on an IVF programme has not been fully examined. We therefore decided to systematically review the evidence provided in the literature so that we may evaluate a single variable in relation to a successful transfer, the firmness of the embryo transfer catheter.

METHODS

An extensive computerized search was conducted for all relevant articles published as full text, or abstracts, and critically appraised. In addition, a hand search was undertaken to locate any further trials.

RESULTS

A total of 23 randomized controlled trials (RCT) evaluating the types of embryo transfer catheters were identified. Only ten of these trials, including 4141 embryo transfers, compared soft versus firm embryo catheters. Pooling of the results demonstrated a statistically significantly increased chance of clinical pregnancy following embryo transfer using the soft (643/2109) versus firm (488/2032) catheters [P = 0.01; odds ratio (OR) = 1.39, 95% confidence interval (CI) = 1.08-1.79]. When only the truly RCT were analysed, the results were again still in favour of using the soft embryo transfer catheters [soft (432/1403) versus firm (330/1402)], but with a greater significance (P < 0.00001; OR = 1.49, 95% CI = 1.26-1.77).

CONCLUSION

Using soft embryo transfer catheters for embryo transfer results in a significantly higher pregnancy rate as compared to firm catheters.

Cannulation of a resistant internal os with the malleable outer sheath of a coaxial soft embryo transfer catheter does not affect in vitro fertilization–embryo transfer outcome

OBJECTIVE

To assess the impact of cannulation of a resistant cervical os with the outer malleable sheath of a double-lumen, soft ET catheter on IVF-ET outcomes.

DESIGN

Retrospective cohort study.

SETTING

University-based IVF center.

PATIENT(S)

One hundred forty-two patients undergoing 142 ETs.

INTERVENTION(S)

Trial ultrasound-guided ET at all transfers, leaving the malleable outer sheath in situ when the soft inner catheter could not negotiate the internal os.

MAIN OUTCOME MEASURE(S)

Implantation rate and clinical pregnancy rate.

RESULT(S)

In 102 ETs (71.8%), the soft inner sheath easily negotiated the internal os (group 1). Forty ETs (28.2%) required cannulation of resistant internal ora with the outer sheath of the trial catheter (group 2). Implantation rates (35% vs. 32% in groups 1 and 2, respectively) and clinical pregnancy rates (50% vs. 45%) were not significantly different between groups. Blood was present on the transfer catheter after ET more frequently in group 2 than in group 1 (55% vs. 15%); however, neither the implantation rate nor the clinical pregnancy rate were affected by the presence of blood.

CONCLUSION(S)

Cannulation of a resistant internal os by the malleable outer sheath and blood on the transfer catheter after ET do not have an adverse effect on implantation rate or clinical pregnancy rate.

The Impact of Embryo Transfer on Implantation—A Review

Embryo transfer has received little clinical attention and has been, until recently, the most inefficient step in in-vitro fertilization (IVF). In this article, the authors review the literature and their personal experience regarding the process of intrauterine transfer of embryos, which remains the object of much discussion. Factors which appear to influence implantation rates are: contamination of the catheter tip with cervical bacteria, stimulation of uterine contractions during the procedure, the type of catheter, ultrasound guidance during the transfer, and the position of the embryos in the uterine cavity. Easy and atraumatic transfer is essential for successful implantation and the embryos need to be placed in the middle of the cavity, away from the fundus. Knowing, beforehand, the position and length of the uterus can provide better results and may reduce the rate of ectopic pregnancies. Evidence from randomized studies has supported this claim. Despite the number of available studies controlling certain variables, most authors, even using the same catheter, ultrasound guidance and/or a trial transfer use different protocols or similar instruments in different ways. Standardization of the transcervical intrauterine transfer of embryos in a large randomized study is needed before definitive conclusions can be drawn. The goal of improved implantation and pregnancy rates deserve these efforts.