Changing the public perception of human embryology
Human embryos have profound ethical significance which, demands careful consideration. Models developed from stem cells, mimicking embryos, offer insights into developmental principles and stimulate/promote medical progress. Misrepresentation of these models risks distorting research and misleading the public, undermining trust in science.
The authors of the opinion piece are leading experts from around the world and they describe the historic public misperceptions that have hindered progress, the new avenues of human embryo research and the necessity of defining embryo models for scientists and public alike (1). Mistrust in human embryology, stemming from ancient beliefs and modern myths, has hindered scientific progress in the past. The field of medical assisted reproduction faced severe criticism before it became widely accepted, with 4% of all births in Europe resulting from IVF. In a world where moral values are constantly changing, stem cell biologists and embryologists prioritise ethical paths towards understanding human development and addressing medical challenges.
As the authors point out, knowledge of early human embryogenesis originated mostly from donated surplus embryos from patients completing their families through IVF treatment. Nonetheless, research using these embryos does not usually exceed 14 days from fertilisation, if not earlier for some countries. Historically, stem cell research comprised of mouse and human stem cells organising into structures resembling embryos. While these models have limitations and do not form viable organisms, their practicality is an added benefit that can facilitate research, especially in countries where embryo research is restricted. Even though the ability of embryo models to mimic embryogenesis is unknown, they have the potential to reveal important genes, molecules, and cells at play. Rivron et al., indicate that embryo models can fill an important knowledge gap and hold potential for understanding developmental processes, battling infertility and pregnancy loss, as well as revealing the origin of birth defects.
Advancements in embryo models require careful consideration of the ethical framework and governance in regard to their legal status, their use in reproduction and their realistic contribution to science and medicine. The authors suggest that a holistic approach is required from a multidisciplinary team of biologists, ethicists, philosophers, and legal scholars. Discussions among experts and the public have shaped international guidelines for using embryo models responsibly. Recommendations emphasize caution on the use of complete models. Research is only permitted following ethical approval and transfer into a uterus is not permitted. The authors emphasise that use of human embryo models is not always justified from a scientific and ethical perspective, especially when alternatives such as gastruloids, assembloids and organoids are available. These recommendations steer ongoing discussions by national ethics committees to align with societal values as well as from international funding agencies and scientific societies, such as the International Society for Stem Cell Research (ISSCR) and ESHRE. Basic ethical principles have existed since the second half of the 20th century, but political and religious beliefs can hinder research. This is demonstrated by the previous ban of federal funding in the US for human embryonic stem cell research and the existing ban in Germany on using surplus patient embryos.
The challenges in science dissemination are also a major point raised by the authors. The ISSCR fundamental principles state that scientists have a duty to communicate their results in a trustworthy, accessible, and timely manner to maintain public confidence (2). International societies such as ISSCR and ESHRE, local committees such as the Cambridge Reproduction Initiative, and information outlets for journalists such as the Science Media Centre in the UK, Spain, and Germany all aim to provide accurate, diverse, and measured opinions.
Effective communication of scientific results to the public is vital. Transparency, accessibility, and verifiability of data are crucial to maintain public trust. However, premature dissemination, lack of scrutiny, and sensationalism, risk the misinterpretation of information. As the authors state, use of specific language such as ‘synthetic embryos’ by the press gives the impression that these are embryos created from scratch for use in reproduction. Scientists, the media, and press offices play key roles in accurate and measured information dissemination. Correct language, like ‘stem cell-based embryo models’, is crucial for accurate communication and to avoid misconceptions. Moreover, Rivron et al., state that since these models present unknowns regarding their status and contributions to medicine, ethical evaluation should be a continuous exercise.
On this basis, the authors summarise that progress in human embryology requires steady advancement, devoid of sensationalism. Regular re-evaluation of ethical considerations and governance policies is crucial. Scientists engaging with the public can enhance accurate information dissemination, building a stronger foundation for impactful human embryology.
1. Rivron, N.C., Martinez-Arias, A., Sermon, K. et al. Changing the public perception of human embryology. Nat Cell Biol 25, 1717–1719 (2023). https://doi.org/10.1038/s41556-023-01289-4
2. International Society for Stem Cell Research. Guidelines for Stem Cell Research and Clinical Translation. International Society for Stem Cell Research. https://www.isscr.org/guidelines.
BMI in the range of 23 to 24.99 kg/m2 is linked with highest chance of clinical pregnancy and live birth
Data reported to the SART registry continues to provide insights into the link between BMI and IVF pregnancies, and adds to the debate around the use of BMI to determine IVF eligibility.
An updated review (1) recently reported in Focus on Reproduction found that frozen embryo transfer (FET) success decline as BMI in women increases in cases of female (but not male) factor infertility.
BMI was categorised according to World Health Organization (WHO) guidelines with 18.5 to 24.9 kg/m² defined as normal weight.
Now a new SART analysis (2) suggests that the highest probability of clinical pregnancy and live birth is associated with patients whose BMI is within the specific range from 23 to 24.99 kg/m2. Based on more than 77,000 PGT-A cycles from nearly 56,000 patients, the study showed that underweight (BMI below 18.5kg/m2) patients were 11% less likely to have a live birth and those with a BMI of 40 kg/m2 and above were 27% less likely.
In line with the earlier review, the authors question the use of BMI as a cut-off for fertility treatment provision; and suggest alternatives to BMI for measuring body fat.
Prior studies have demonstrated that obesity has many effects on IVF outcomes including decreased LBR. While the exact mechanism is unknown, this has been attributed to factors including altered uterine milieu and decreased oocyte quality. However, not all data on the effect of BMI are consistent in terms of IVF outcomes.
The focus of this analysis based on FETs reported to SART between 2014 to 2017 was to determine if BMI was associated with live birth in patients undergoing transfer of frozen-thawed PGT-A embryos. It comprised 77,018 PGT-A cycles of which 70,752 were autologous and 6,266 donor egg recipients.
The authors write that the study population of 55,888 patients was strictly defined to include only frozen-thawed PGT-A-tested blastocyst cycles. This allowed them to refine the association of BMI with cycle outcome when the ploidy status of the embryo is known.
In the autologous and donor cycles, results showed what the authors describe as a ‘statistically significant and clear non-linear relationship’ between BMI and LBR, with the highest birth rates observed in the ideal reference range (BMI 23 to 24.99 kg/m2).
In contrast, those not in the ideal range demonstrated a lower probability of live birth and clinical pregnancy that continued to decrease the further the BMI became from the reference value. Patients with a BMI below 18.5 or a BMI of 40 and above had lower probabilities of live birth.
When the data were stratified by age, increased rates of live birth were observed across all ages at the ideal range (except endometriosis) but women aged over 40 years had a lower clinical pregnancy rate. This is despite PGT-A testing which suggests that aneuploidy is not the reason for higher miscarriage rates in women who are obese and who used euploid embryos.
Another key observation was prompted by the fact that outcomes in both autologous and donor egg recipient cycles were linked to the intended parent’s BMI. Hence, the authors theorise that extremes of weight are ‘likely associated with a malfunction in the implantation process’, presumably related to a uterine (not oocyte) factor. However, some blastocysts could have been low-level mosaics because the study surmised that all embryos transferred after PGT-A were euploid.
What do the results mean for clinical practice around weight, BMI and eligibility for IVF? Weight loss prior to conception has been standard advice to couples prior to IVF. Nevertheless, this is not a recommendation of this study. Instead, the authors cite data that weight loss interventions prior to an IVF cycle (3) do not improve the live birth rate.
The authors state that in the US there is no nationally recognized BMI threshold to provide fertility treatment. BMI is just one datapoint and that more exact measurements of percent body fat could be provided, they argue. For example, a recent study found that bioelectric impedance analysis did not differ significantly from BMI (4).
For women of reproductive age with BMIs outside the normal range of BMI 18.5 to 24.9 kg/m², it remains unclear what medical treatment or lifestyle changes may be beneficial. . The focus for future research should be on filling this knowledge gap, the authors emphasise.
REFS:
1 Bakkensen JB, Strom D and Boots CE. Frozen embryo transfer outcomes decline with increasing female body mass index with female but not male factor infertility: analysis of 56,564 euploid blastocyst transfers. Fert and Steril (2023); doi: https://doi.org/10.1016/ j.fertnstert.2023.07.027.
2 Peterson A, Wu H, Kappy M, Kucherov A, Singh M, Lieman H, Jindal S. Higher live birth rates are associated with normal BMI in PGT-A FET cycles: a SART CORS study. Fert and Steril (2023); doi: https://doi.org/10.1016/j.fertnstert.2023.11.005.
3 Legro RS et al. Effects of preconception lifestyle intervention in infertile women with obesity: The FIT-PLESE randomized controlled trial. PLoS Med. 2022 Jan 18;19(1):e1003883. doi: 10.1371/journal.pmed.1003883. PMID: 35041662; PMCID: PMC8765626.
4 Kim et al. The Appraisal of Body Content (ABC) trial: Increased male or female adiposity does not significantly impact in vitro fertilization laboratory or clinical outcomes. Fert and Steril Feb 2021; https://doi.org/10.1016/j.fertnstert.2020.12.037
Egg freezing and how to improve outcomes
RCT finds that previously unobserved factors contribute to oocyte aneuploidy in women aged over 35
The older a woman is, the greater the risk that her embryos will be affected by multiple chromosome abnormalities. And the widely held view is that these errors are caused solely by chromosome mis-segregation during both stages of cell division in meiosis.
However, that belief has now been challenged by the authors of a multicentre RCT who say other factors should also be considered. Through thorough chromosomal analyses of a high number of polar bodies (PBs), their study provides evidence of frequent unexpected chromosomal segregation during oogenesis. It also allows better understanding of the effects of chromosomal abnormalities present in the oocyte on embryo development.
The findings (1) based on data sourced from the ESTEEM trial (2) represent one of the largest analyses of its kind, and add to the understanding of low pregnancy rates, pregnancy loss and birth defects among advanced maternal age (AMA) women.
In their recently published paper, the authors write that their results indicate that knowledge of the mechanisms causing aneuploidy in oocytes is ‘incomplete’. They go on to say that their finding around copy numbers ‘challenges the dogmas that aneuploidy in oocytes is exclusively caused by mis-segregation of chromosomes during MI (meiosis I) and MII (meiosis II).’
To date, there has been little research into the underlying mechanisms which give rise to an abnormal number of chromosomes during female meiosis. The studies that have explored this issue have only included a small number of PB pairs for analysis.
The original ESTEEM trial was performed in seven European centres to assess if genetic testing for aneuploidy (PGT-A), by screening both PBs using array comparative genomic hybridization, increased the chance of live birth in ICSI patients aged 36 to 40 years compared with ICSI without PGT-A.
The present study re-evaluated the ESTEEM data based on 693 PB pairs from 396 advanced maternal age women (AMA) (n=205 PGT-A intervention group; n=191 control). This was to characterise the types of chromosomal abnormalities and the chromosomes most frequently affected.
In addition, the aim was to determine what processes take place in the oocytes of AMA patients to cause aneuploidy, and to evaluate any correlation with embryo quality.
The morphology from 1,034 embryos generated from fertilized oocytes (two pronuclei) in the PB biopsy group and 1,082 in the control group were used for statistical analysis.
Results showed that more than two-thirds (n=461/693) of PB pairs showed abnormal segregation in 1,162 out of 10,810 chromosomes.
Of these abnormal segregations, the majority (n=1,050/1,162; 90%) were known segregation errors. Almost half were compatible with precocious separation of sister chromatids in MI (n=568/1,162; 48.9%), over a third with non-disjunction (ND) of chromatids in MII or reverse segregation (n=417/1,162; 35.9%), and less frequently ND in MI (n=65/1,162; 5.6%).
However, the authors say unknown errors were identified in 10% of chromosomes (n=112/1,162) with abnormal PB segregation. In these cases, they say they observed a (chromosome) copy number in the first PB and second PB that could not be explained ‘by any of the known mechanisms causing aneuploidy in oocytes’.
The authors suggest that premeiotic aneuploidy could explain their findings; or alternatively anaphase lagging may have occurred.
Embryos in the PGT-A arm of the RCT did not have a significantly different morphology between 2- and 6-days post-insemination compared to the control group. As such, this indicates that PB biopsy did not affect embryo quality.
Age-adjusted analysis was performed for each embryo evaluation day. Results showed aneuploidy was associated with a decrease in embryo quality on Day 3 (adjusted odds ratio (aOR) 0.62, 95% CI 0.43–0.90), Day 4 (aOR 0.15, 95% CI 0.06–0.39), and Day 5 (aOR 0.28, 95% CI 0.14–0.58). This novel finding that shows embryo development and oocyte chromosome status are interlinked; and is without biased unlike the selection of embryos for biopsy, say the authors.
Limitations of the study included the fact that it was performed in several laboratories and IVF units. The consequence is that the interpretation of results may have varied between centres.
Analysis of oocyte aneuploidy could only be carried out indirectly by PB testing because the oocyte/embryo was unavailable for confirming the expected segregations.
The authors say that the ‘significant number’ of PBs analysed allowed them not only to detect unexpected types of chromosomal segregation, but also to understand better the effects of abnormal meiosis on embryo development.
This enhanced understanding, they add, could lead to intervention strategies in future that could ‘mitigate these detrimental effects’ and reduce the risk of their occurrence.
References:
1 Verdyck P, Altarescu G, Santos-Ribeiro S, Vrettou C, Koehler U, Griesinger G, Goossens V, Magli C, Albanese C, Parriego M, Coll L, Ron-El R, Sermon K, Traeger-Synodinos J. Aneuploidy in oocytes from women of advanced maternal age: analysis of the causal meiotic errors and impact on embryo development. Hum Reprod 2023; dead201, https://doi.org/10.1093/humrep/dead201
2 Verpoest W, Staessen C, Bossuyt PM, Goossens V, Altarescu G, Bonduelle M, Devesa M, Eldar-Geva T, Gianaroli L, Griesinger G, Kakourou G, Kokkali G, Liebenthron J, Magli MC, Parriego M, Schmutzler AG, Tobler M, van der Ven K, Geraedts J, Sermon K. Preimplantation genetic testing for aneuploidy by microarray analysis of polar bodies in advanced maternal age: a randomized clinical trial. Hum Reprod. 2018 Sep 1;33(9):1767-1776. doi.org/10.1093/humrep/dey262. PMID: 30085138
Job loss linked to stillbirth and miscarriage
The risk of miscarriage and stillbirth almost doubles if a woman or her partner lose their job during pregnancy, according to the first analysis (1) of its kind. This is compared with those who are not made involuntarily redundant after they conceive.
Based on data from more than 8,000 pregnancies and nearly 5,000 women in the UK, the findings suggest that some pregnancy losses can be prevented, according to the authors.
The results show the odds of a non-live birth are more than 20% for pregnancies where one or both parents-to-be is made redundant whereas the figure is 12% if no job loss occurs.
The authors urge policymakers to improve measures to protect labour markets and social security systems to safeguard pregnant women and their partners.
Economic downturns, stressful life events and intense working hours have all been studied previously in the context of pregnancy loss. However, there has been little analysis of whether job loss disrupts the course of pregnancy, according to the authors.
This knowledge gap needs addressing, they say, given that job loss has ‘far-reaching consequences for women’ and their families.
On this basis, the study set out to provide evidence on the link between involuntary termination of employment and pregnancy disruption (ie miscarriage and stillbirth), starting from the time of conception and ending with pregnancy outcome.
The data was drawn from Understanding Society (2), the UK Household Longitudinal Study (UKHLS) which has a sample size of 40,000 representative UK households (approximately 100,000 individuals). Conducted annually from 2009 to 2022, the UKHLS features self-reported information from women.
The sample used from the UKHLS for this present study represented 8,142 pregnancies among 4,942 women (and partners where relevant). Predicted outcomes were pregnancy loss or live birth, and the risk of pregnancy loss from either partner’s involuntary job loss because of redundancy or dismissal.
The authors write that an advantage of the UKHLS is that it records the length in months of any gestation that ends prematurely in a non-live birth; and the timing of a job loss also in months. As such, they were able to combine this information to determine if the exposure to job loss occurred during the pregnancy and at what stage.
Statistical analysis was carried out using 3 models. For model 1, the authors estimated a baseline to predict the risk of a non-live birth. This included the primary exposure variable and covariates for women’s demographic characteristics and background (age, ethnicity, and parents’ social class), the experience of a prior pregnancy loss, and year and month fixed effects.
Model 2 assessed highest educational attainment, marital status, and health additional to the demographic characteristics used in the first model; and model 3 included socio-economic status of the partner and household income in addition to the characteristics used in the first 2 models.
Pregnancy loss was defined as a pregnancy that did not result in a live birth, miscarriage as a loss before the 24th week of pregnancy, and stillbirth as a loss after the 24th week. Study exclusions from the main analysis included pregnancy termination, ongoing pregnancy at time of interview, and job loss that involved factors such as a contract termination and illness.
Results showed that around 1 in 10 (n=985; 11%) of the total pregnancies (n=8142) resulted in miscarriage or stillbirth; and job loss occurred among less than 1% (n=136) of pregnancies.
Of the 136 pregnancies where job loss has taken place, pregnancy loss occurred almost a quarter (24% overall; miscarriage=23.5%; stillbirth 0.7%) vs the 12% of pregnancies where there was no job loss. This represented an increased risk for the job loss group (odds ratio (OR)=1.99, 95% CI: 1.32-2.99).
The authors say that this association between pregnancy disruption and job loss ‘remained robust’ for model 2 (OR=1.83, 95% CI: 1.22-2.75) and model3 (OR=1.81, 95% CI: 1.20-2.73).
Strengths of the study included the fact the authors could distinguish between involuntary and anticipated causes of job loss. Among the limitations were the small sample size and the fact participants self-reported the date/outcome of conception.
So, what mechanisms are at work that cause job loss to lead to pregnancy disruption? Even though this was not an aim of the study, the authors cite evidence that stress results in the production of hormones (eg cortisol) which are known to increase the risk of miscarriage. Moreover, a reduction in available income could restrict access/compliance to prenatal care.
In conclusion, the authors suggest their analysis be replicated in different countries to assess the validity of the findings from a global viewpoint. This would also identify the extent to which measures against unemployment help reduce the impact of job loss on pregnancy outcomes.
Refs:
1 Di Nallo A, Selin Köksal S. Job loss during pregnancy and the risk of miscarriage and stillbirth. Human Reprod, vol 38(11) Nov 2023; 2259–2266;
https://doi.org/10.1093/humrep/dead183
2 https://www.understandingsociety.ac.uk/live birth ratemiscarriage
Co-treatment with an aromatase inhibitor during ovarian stimulation does not impact oocyte, embryo and pregnancy outcomes
Secondary outcomes of the double-blinded, placebo-controlled RIOT (Reducing the Impact of Ovarian sTimulation) study (1), indicate that a once-daily dose of the aromatase inhibitor used in combination with gonadotropins has no negative impact on follicle recruitment, oocyte number, embryo quality and live birth rate (LBR).
The results, based on over 1,200 retrieved oocytes and over 300 embryos, support the use of LZ as a co-treatment in specific cases. The authors say that patients undergoing fertility preservation, with previous cancer, at risk of cancer, or poor responders could benefit from the drug which lowers the level of circulating oestrogens.
Letrozole has been successfully used in medical assisted reproduction since 2001. The hormone therapy was used initially for ovulation induction in intrauterine insemination, then for fertility preservation in women at risk of breast cancer, or those with previous oestrogen-dependent cancers and other indications.
When used as a co-treatment, the aromatase inhibitor is believed to synergize with gonadotropin stimulation in IVF protocols, which may lead to a higher number of retrieved oocytes and embryos. This is compared to treatment with gonadotropins alone.
However, there are concerns that the lower levels of oestradiol in the follicular cavity may harm the oocyte and lead to higher rates of abnormal fertilization, as suggested by a recent systematic review (2). Overall, the effect and safety profile of LZ co-treatment in IVF is controversial and contrasting data have been published.
The Danish RIOT trial investigated the effect of LZ intervention during stimulation for IVF with the gonadotropin FSH. It was conducted in four Danish fertility clinics at university hospitals from August 2016 to November 2018, and pregnancy outcomes were registered until May 2023.
Previous results reported by the RIOT authors indicated that LZ co-treatment during IVF had no effect on the premature rise in progesterone levels, an event that is believed to disrupt the normal endocrine milieu and impact on reproduction outcomes (3).
Now, the authors present the secondary outcomes of the RIOT trial, describing the effect of LZ co-treatment on follicle recruitment, oocyte number and quality, embryo quality and live birth.
A total of 159 women with normal ovarian reserve were randomized to either LZ co-treatment (5mg once daily) or placebo. This resulted in 1,268 aspirated oocytes and 386 developed embryos.
Finding show that there was no difference in the number of retrieved oocytes, in the size and number of aspirated follicles and in the proportion of usable embryos between study groups. Blastocysts and vitrified blastocysts per patient on Day 5, as well as vitrified blastocysts on Day 6, were similar in the LZ and placebo groups.
Usable embryos were assessed by morphology and resulted in similar distribution of ‘good’, ‘fair’ and ‘poor’ morphology between study groups. Additionally, morphokinetics, applied to 295 embryos, showed that the odds of having a high KIDscore™ were 1.2 times higher in the LZ vs placebo group (CI: 0.8 – 1.9, P = 0.68).
The cumulative clinical pregnancy rate was 31% vs 39% in the LZ and placebo group respectively, which is not statistically different. In addition, the cumulative pregnancy rate did not differ after adjustment for day of transfer; oestradiol and progesterone levels at trigger; progesterone levels at mid-luteal phase; and number of oocytes. Early and foetal miscarriage rates did not differ between LZ and placebo-treated women.
Finally, LBR also showed comparable results in the LZ and placebo arms.
The authors conclude that LZcan be considered as a co-treatment in IVF when it is necessary to prevent high blood oestradiol levels because the hormone therapy does not have a significant impact on the oocyte, embryo development and pregnancy outcome. Cases where LZ could be used include poor responders with previous oncologic conditions or women at increased risk of cancers.
However, they say that routine implementation of LZ co-treatment in expected normal responders is not recommended and that further investigation is needed of the drug’s effect on mature oocytes from follicles with different sizes.
The authors say there may be biases in their results due to laboratory factors because of the multicentre design of the study and because oocytes and embryo quality were secondary outcomes; hence, prone to type II error.
In addition, they disclosed potential conflicts of interest due to the financial involvement of the pharmaceutical industry in the study.
1 Bülow NS et al. Impact of letrozole co-treatment during ovarian stimulation on oocyte yield, embryo development, and live birth rate in women with normal ovarian reserve: secondary outcomes from the RIOT trial. Hum Reprod vol 38 (11) November 2023; 2154–2165; https://doi.org/10.1093/humrep/dead182
2 Bonardi B et alet al. Efficacy and safety of controlled ovarian stimulation with or without letrozole co-administration for fertility preservation: a systematic review and meta-analysis. Front Oncol 2020;10:574669. https://doi.org/10.3389/fonc.2020.574669
3 Bülow NS et al. Impact of letrozole co-treatment during ovarian stimulation with gonadotrophins for IVF: a multicentre, randomized, double-blinded placebo-controlled trial. Human Reprod vol 37 (2) February 2022; 309–321; https://doi.org/10.1093/humrep/deab249
No benefit from laser-assisted hatching for subfertile couples
This is the message from the authors of a double-blinded, multicentre randomised controlled trial (RCT) (1) that also suggests that fertility providers should offer assisted hatching at no extra cost, and preferably only provide assisted hatching within a clinical trial setting.
Based on more than 500 couples with recurrent implantation failure (RIF), the findings cast yet more doubt on the benefits of adjuvant fertility treatments which have been criticised by regulators for being costly and ineffective.
The study failed to find any statistically significant evidence that assisted hatching – a procedure developed more than 30 years ago to facilitate sperm penetration – improves live birth rates (LBR) among subfertile RIF patients.
Moreover, the Dutch team who carried out the RCT write that they cannot ‘exclude the possibility that assisted hatching decreases the live birth rates.’
Such is the controversy around add-ons that more than 200 comments were received by a (now closed) stakeholder review of the first ESHRE guidance (2) on adjuvants. The ESHRE Add-ons working group reviewed 27 treatments and none are recommended for routine clinical practice in the final good practice document published recently in Human Reproduction.
In the case of assisted hatching, some meta-analyses have suggested that poor prognosis women, especially RIF patients, might benefit most from this technique. However, the committee who drew up ESHRE’s recently published recommendations on RIF (3) state that the phenomenon has become associated with poor and even exploitative practice, and advises against ‘uncontrolled use’ of add-ons.
The ESHRE RIF guidance was not available when this RCT was carried out in the Netherlands. But the authors do reference the knowledge gap around assisted hatching with a recent Cochrane review concluding the quality of evidence is very low to low.
As such, the study designed the RCT to show if assisted hatching does/does not increase the cumulative LBR in subfertile couples who experience RIF.
The study was performed at the laboratory sites of three tertiary referral hospitals and two university medical centres in the Netherlands. Participants were eligible for inclusion after having had either at least two consecutive fresh IVF or ICSI embryo transfers.
This included transfer of frozen and thawed embryos originating from those fresh cycles, and which did not result in a pregnancy; or at least one fresh IVF or ICSI transfer and at least two frozen embryo transfers with embryos originating from that fresh cycle which did not result in a pregnancy.
Participants were included and randomised from November 2012 until November 2017. A total of 297 subfertile couples were allocated to the assisted hatching and 295 to the control to demonstrate a statistically significant absolute increase in live birth rate of 10% after assisted hatching.
Block randomisation (n=20 participants per block) was applied and randomisation was concealed from participants, treating physicians, and laboratory staff involved in the embryo transfer procedure.
Ovarian hyperstimulation, oocyte retrieval, laboratory procedures, embryo selection for transfer and cryopreservation, the transfer itself, and luteal support were performed according to local protocols.
Procedures were identical in both the intervention and control arm of the study with the exception of the assisted hatching, which was only performed in the intervention group. Laboratory staff performing the assisted hatching were not involved in the embryo transfer itself.
Results showed that the cumulative LBR per started cycle, including the transfer of fresh and subsequent frozen/thawed embryos if applicable, resulted in 77 live births in the assisted hatching group (n=297, 25.9%) and 68 live births in the control group (n=295, 23.1%). This did not prove to be statistically significant (relative risk: 1.125, 95% CI: 0.847 to 1.494, P=0.416).
Miscarriage rates were shown to decrease after assisted hatching, a finding that was statistically significant. However, the authors suggest this may be down to chance and caution that this should not be used as an indication for offering the add-on.
The authors acknowledge that a small cohort of subfertile couples who did not achieve an ongoing pregnancy still had cryopreserved embryos in storage at the endpoint of the trial (1 year after the last randomisation).
Hence, they cannot exclude that future transfer of these frozen/thawed embryos will increase the cumulative LBR in either/both study arms.
In addition, the authors write that they cannot rule out that assisted hatching might be effective in higher order RIF because there was no international consensus on the definition of RIF when they started the study.
1 Max H J M Curfs, Ben J Cohlen, Els J Slappendel, Dick C Schoot, Josien G Derhaag et al. A multicentre double-blinded randomized controlled trial on the efficacy of laser-assisted hatching in patients with repeated implantation failure undergoing IVF or ICSI. Hum Reprod 2023; https://doi.org/10.1093/humrep/dead173
2 ESHRE Add-ons working group: K. Lundin, J.G. Bentzen, G. Bozdag, T. Ebner, J. Harper , N. Le Clef, A. Moffett, S. Norcross, N.P. Polyzos, S. Rautakallio-Hokkanen, I. Sfontouris , K. Sermon , N. Vermeulen, and A. Pinborg. Good practice recommendations on add-ons in reproductive medicine. Human Reproduction 2023 (0), 1–43 https://doi.org/10.1093/humrep/dead184
3 ESHRE Working Group on Recurrent Implantation Failure, D Cimadomo, M J de los Santos, G Griesinger, G Lainas, N Le Clef, D J McLernon, D Montjean, B Toth, N Vermeulen, N Macklon. ESHRE good practice recommendations on recurrent implantation failure. Hum Reprod Open 2023 (3) https://doi.org/10.1093/hropen/hoad023
Sifting through add-ons in ART: seeking clarity and the path forward
The Human Fertilisation and Embryology Authority (HFEA), the UK fertility regulator, has been a forerunner on the topic. The HFEA’s well know traffic light list of add-ons has been updated in October 2023. The new rating system has five-categories that indicate whether a treatment add-on is effective at improving treatment outcomes for someone undergoing fertility treatment, according to evidence from scientific studies. The new ratings also show whether a particular patient group would benefit from each add-on2. In addition to the improved rating system, HFEA, with ESHRE as signatory, has launched a consensus statement mentioning that “where there is no evidence to support safety and efficacy, treatment add-ons should only be offered to patients in a research setting with sound methodology and approval from a research ethics committee”3.
A multitude of add-ons are available in clinical practice. A recent good practice recommendation paper from ESHRE has examined the evidence for 27 groups of tests and interventions. Following thorough evaluation, only five could be recommended or considered in clinical practice (hyaluronic acid addition to transfer media, microfluidics), including some listed as effective only for selected patient groups (artificial oocyte activation, artificial sperm activation, screening hysteroscopy) based on an evaluation of published evidence of their efficacy and safety as well as other factors such as biological rationale1. The list of tests and interventions that are not recommended is extensive. The non-recommendations are primarily based on lack of effectiveness in terms of improving live birth rates, evidence of possible or confirmed side-effects and harms, or a lack of data for either efficacy or safety.
So, the question arises of whether all these add-ons are bad. The authors of the good practice recommendations say in the paper that its purpose is “not to discourage ongoing or future research.“ In fact, they call for more research and studies on the relevance of the “add-ons that have a clear rationale”, even if they acknowledge that research is not always feasible owing to difficulties with low numbers of patients or rare conditions, or in obtaining research funding. To counteract these difficulties, the authors urge clinics to “monitor and follow up on non-established interventions and share the results with other clinics to gather sufficient data for meaningful conclusions”. Needless to say, once research has convincingly shown that an add-on is effective and safe, it is no longer valid to label it as an add-on.
Even when further studies become available, it is clear that add-ons are, and likely will remain, part of clinical practice. New interventions will be introduced, and current ones may be modified. If shown to be safe, some may be applicable for use in specific cases or patient groups. Personalisation in medicine means tailoring treatments to a specific patient or couple, whether based on genetic tests, the presence of biomarkers, other phenotypic findings or observed responses to treatment. In reproductive medicine, the infertility work-up and ovarian response are already considered key drivers to guide the appropriate ART treatment. In future, genetic testing may be added to this as new genes and gene-disease relations are discovered on a weekly basis and first steps are taken to include genetic testing in the infertility work-up and use its results for targeted treatment4. A scholarly example of personalised medicine in ART is ICSI, which has a clear rationale for couples with male factor infertility and has shown benefit in this specific population. Artificial oocyte activation may be a last straw of hope for cycles with complete activation failure (0% 2PN), very low fertilisation (<30%), or patients with globozoospermia, but it should remain a no-go for standard ART cycles. And this is part of the problem: applying interventions that demonstrated (some) benefit in a certain subgroup to all ART patients. The reasons behind the wider application range from despair of patients to conflicts of interest for healthcare professionals.
It is still to be determined whether there is a specific subgroup of patients that can benefit from e.g. sperm DNA damage testing, physiological ICSI (PICSI), or even PGT-A. However, employing add-ons indiscriminately across all patients with the expectation that some might benefit is not a sustainable approach. As a community, our goal should be to foster further research into these interventions grounded in a clear rationale. This is with the hope that, in the coming years, some of the interventions now listed as add-ons will demonstrate safety and potential effectiveness for a specific target group. If the evidence becomes compelling, tailored and personalised implementation of these interventions may be included in future ESHRE recommendations.
Meanwhile, one can only hope that the ESHRE recommendations can assist healthcare professionals that aim to assist women and men in having children in resisting– what is sometimes substantial- pressure from patients to use add-ons. Education of patients and public is important in that respect and will be a next goal for the working group.
- ESHRE Add-ons working group, K Lundin, J G Bentzen, G Bozdag, T Ebner, J Harper, N Le Clef, A Moffett, S Norcross, N P Polyzos, S Rautakallio-Hokkanen, I Sfontouris, K Sermon, N Vermeulen, A Pinborg, Good practice recommendations on add-ons in reproductive medicine, Human Reproduction, 2023; dead184, https://doi.org/10.1093/humrep/dead184
- https://www.hfea.gov.uk/treatments/treatment-add-ons/
- https://www.hfea.gov.uk/media/kublgcp3/2023-10-19-treatment-add-ons-consensus-statement.pdf
- Van Der Kelen A, Okutman Ö, Javey E, Serdarogullari M, Janssens C, Ghosh MS, Dequeker BJH, Perold F, Kastner C, Kieffer E, Segers I, Gheldof A, Hes FJ, Sermon K, Verpoest W, Viville S. A systematic review and evidence assessment of monogenic gene-disease relationships in human female infertility and differences in sex development. Hum Reprod Update. 2023 Mar 1;29(2):218-232. doi.org/10.1093/humupd/dmac044
ART couples experience lower risk of anxiety and depression in pregnancy
The psychological impact of ART in pregnancy is important because it may affect offspring health, but data has been mixed. Some studies have reported that anxiety and depression are greater with ART while others have found no difference – or even lower rates. This inconsistency in the evidence prompted a recent review (1) to call for more research.
Now a large prospective cohort study (2) suggests that differences exist in populations and may influence psychosocial wellbeing among parents-to-be.
The data from more than 180,000 women and their male partners show that ART couples report lower overall levels of anxiety/depression during pregnancy compared to expectant parents who conceive spontaneously. However, according to a sub-sample analysis of couples who conceived both with ART and spontaneously, fertility treatment was associated with increased maternal anxiety and depression in early pregnancy (17 weeks of gestation). For the reported study, there was no difference at 30 weeks of gestation between ART and spontaneous conception.
This is the first study of its kind to examine mental health difficulties in the same expectant parents, across different types of pregnancies and at two specific timepoints.
The authors say their findings on maternal and paternal mental health and relationship satisfaction help to ‘disentangle some of the mechanisms related to pregnancy-specific treatment’. They add: “Conceiving a child through ART is often a long and stressful process that can cause emotional strain’”.
Data came from the Norwegian Mother, Father and Child Cohort Study (MoBa), which includes 111,143 mothers (spontaneous conception n=108,183; ART n=2,960) and 76,594 fathers.
Of these, a sub-sample of 497 expectant parents (not all were matched couples) had two consecutive pregnancies: one resulting from ART and one spontaneous (n=286 mothers; n=211 fathers), and the majority had their ART pregnancy first.
Women self-reported their symptoms of anxiety and depression such as worrying too much, feeling constantly frightened/anxious, or feeling blue.
Female study participants completed a questionnaire at two timepoints during each pregnancy (at weeks 17 and 30); while male participants did so at one timepoint (week 17). Couples reported their relationship satisfaction at 17 weeks of gestation.
Results showed that pregnancy after ART was associated with less total anxiety and depression, and greater relationship satisfaction among both women and men, compared to spontaneous conception.
However, in the sub-sample of parents where each couple had experienced both ART and spontaneous pregnancies, ART was associated with increased levels of maternal anxiety and depression at 17 weeks of gestation, compared to spontaneous pregnancies (mean=1.19 and mean=1.15, respectively).
This association was not observed in the late stages of pregnancy: anxiety and depression at 30 weeks of gestation were similar for ART and spontaneous pregnancies.
In the sub-sample, expectant fathers reported similar levels of anxiety and depression at 17 weeks of gestation during both pregnancies (ART and spontaneous).
Among women, relationship satisfaction was higher following ART conception than spontaneous conception, a trend the authors say may be explained by the ‘shared challenge of going through infertility; which necessitates enhanced communication, intimacy and closeness between partners’.
Limitations of the study, as outlined by the authors, included the potential for bias due to the rarity of women having conceived through both ART and spontaneous conception in their first two pregnancies.
In addition, they write that important predictors of mental health in the context of the ability to conceive were not assessed e.g., previous miscarriages and long-term infertility. These warrant exploration in future research, say the authors.
They add that previous discrepancies in the literature on the impact of ART on mental health in pregnancy may be related to ‘inherent differences’ between the groups of parents receiving reproductive treatment and those who did not.
In an attempt to explain mixed findings from earlier studies, the authors say these may relate to the ‘use of cross-sectional designs that do not account for confounding factors such as differences in socioeconomic status (and) a history of mental illness’.
Variations in gestational age when anxiety and depression were assessed by previous researchers may also have been a factor.
What the study does indicate is that women’s emotional health may be influenced by the emotional strain of infertility treatment. However, on a reassuring note, the authors write that this impact on emotional wellbeing ‘seems temporary’.
1 Capuzzi E et al. Is in vitro fertilization (IVF) associated with perinatal affective disorders?. Journal of Affective Disorders 2020; vol 277; 271-278; https://doi.org/10.1016/j.jad.2020.08.006
2 Oftedal A, Tsotsi S, Kaasen A, Mayerhofer L JK, Espen Røysamb et al. Anxiety and depression in expectant parents: ART versus spontaneous conception. Hum Reprod, vol 38 (9) September 2023; 1755–1760, https://doi.org/10.1093/humrep/dead133
