Monthly IVF research brief for December 2024

Here you’ll find a brief summary of new IVF studies for December* that I think are helpful for patients. I’ll be updating this post each week of December with new studies, before making a separate post for next month.

*Note that the publication dates of these studies might be outside of the indicated period, mostly because of how PubMed indexes the article.

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Week 1 (Dec 3 – Dec 9)

Age-related uterine changes and its association with poor reproductive outcomes: a systematic review and meta-analysis. This meta-analysis combined the results of 59 studies that investigated the impact of age on reproductive outcomes in women >35. They found that older women had a thinner endometrium, a reduced chance of clinical pregnancy (using donor eggs) and a higher chance of pregnancy loss.

Immune system regulation of physiological and pathological aspects of the ovarian follicle pool throughout the female reproductive lifespan. This review describes how the immune system influences the growth and condition of follicles, and how it impacts ovarian reserve and contributes to issues like premature ovarian insufficiency. This review mainly focuses on research in animal models.

Embryology outcomes of a device-based sperm separation technique compared to density gradient centrifugation using thawed spermatozoa—a sibling donor oocyte study. This study tested two methods, the Zymot sperm separation device and traditional density gradient centrifugation, for preparing sperm from frozen samples and their effects on embryo development. The results showed that both methods were similar in early embryo stages, but Zymot led to a higher number of better quality embryos.

Abnormalities of Oocyte Maturation: Mechanisms and Implications. This is a review of egg maturation mechanisms, and discusses the role of mitochondrial activity, oocyte activation by calcium ions and cumulus cells.

Mitochondrial dysfunction in pregnancy loss: a review. This review explores the relationship between mitochondrial dysfunction and pregnancy loss, considering how flaws in crucial developmental processes like embryo health, endometrial receptivity and maternal-embryo communication can lead to pregnancy loss.

Week 2 (Dec 10 – 16)

The impact of age and number of oocytes retrieved on the cumulative live birth rate in women with poor ovarian response: A 15-year study. This study investigated the impact of age and the number of eggs retrieved on the cumulative live birth rate in women with poor ovarian response. It found that both age and the number of eggs independently affect the cumulative live birth rate, with each additional egg retrieved significantly increasing the chances of a successful live birth, particularly in younger women compared to those aged 43-45.

Effects of preimplantation genetic testing for aneuploidy on embryo transfer outcomes in women of advanced reproductive age with no more than three retrieved oocytes. This study compared PGT-A outcomes for women 38 years or older with 3 or fewer eggs retrieved. They found that PGT-A cycles were at higher risk of cancellation, but resulted in a higher chance of pregnancy and live birth per transfer. While there were differences per transfer, there were no differences per cycle.

Mechanism of Endometrial Receptivity Affected by Fibroids. This review examines how fibroids, particularly submucosal and some intramural types, influence endometrial receptivity and pregnancy outcomes through mechanisms such as cytokine secretion, altered blood flow and angiogenesis, impacts on endometrial peristalsis, and changes in the uterine microenvironment.

Greater PGT-A utilization in IVF clinics does not improve live birth rates but relates to IVF center ownership: a preliminary report. This study analyzed over 90% of US IVF clinics, examining the correlation between PGT-A useage and live birth rates, stratified by patient age and clinic ownership types (physician, academic/hospital/military, equity/venture capital). It found that clinics with the lowest PGT-A use had better live birth outcomes, particularly in younger patients under 35, and that equity/venture capital-owned clinics were more likely to use PGT-A compared to other ownership types. Note that this study was conducted by Norbert Gleicher, a critic of PGT-A who opposes its widespread use.

Complex aneuploidy triggers autophagy and p53-mediated apoptosis and impairs the second lineage segregation in human preimplantation embryos. This study explores how cells in a blastocyst with complex aneuploidy can trigger pathways to destroy the cell (apoptosis), potentially explaining the developmental failure of fully aneuploid embryos and the selective elimination of aneuploid cells in mosaic embryos during self-correction.

Weeks 3 and 4 (Dec 17 – 30)

I combined these weeks because of the holidays.

Culture media with antioxidants improved preimplantation embryo development and clinical outcomes of patients of advanced age. This study investigated the effects of adding antioxidants to the culture media used in growing embryos in the IVF lab. It found that fertilization and early embryo development improved with antioxidant use, along with higher rates of implantation and live births, particularly in older patients.

The role of probiotics in restoring the Th1 to Th2 ratio in women experiencing recurrent implantation failure; a double-blind randomized clinical trial. This randomized clinical trial explored the potential of probiotics in correcting immunological imbalances, specifically the Th1 to Th2 cytokine ratio, to improve outcomes in women with recurrent implantation failure. Results showed that probiotic treatment adjusted immune responses and increased clinical pregnancy rates among RIF patients.

Approximate Bayesian computation supports a high incidence of chromosomal mosaicism in blastocyst-stage human embryos. This study used mathematical models to show that there are high rates of chromosomal errors in embryos, predicting that less than 1% of blastocysts are completely euploid after PGT-A.

A blastocyst’s implantation potential is linked to its originating oocyte cohort’s blastulation rate: evidence for a cohort effect. This study showed that cohorts of eggs retrieved that have a higher rate of developing into blastocysts have a higher chance of implantation, compared to eggs from cohorts with lower blastocyst formation.

The use of a woman’s own eggs in her first IVF treatment at the age of 48 years and 10 months with successful live birth after PGT-A: a case report. This case report details how a nearly 49 year old woman had a live birth after transferring a euploid by PGT-A, on her first try.

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About Embryoman

Embryoman (Sean Lauber) is a former embryologist and the founder of Remembryo, an IVF research and fertility education website. After working in an IVF lab in the US, he returned to Canada and now focuses on making fertility research more accessible. He holds a Master’s in Immunology and launched Remembryo in 2018 to help patients and professionals make sense of IVF research. Sean shares weekly study updates on Facebook, Instagram, and Reddit regularly. He also answers questions on Reddit or in his private Facebook group.

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