Fewer Eggs May Be Just as Successful, Research Shows. New Research Challenges Conventional IVF Approach

In the world of fertility treatments, groundbreaking research is challenging the long-held belief that more eggs retrieved during in vitro fertilization (IVF) lead to better outcomes. Recent studies reveal that women with fewer eggs may have similar success rates to those with many, potentially revolutionizing how fertility specialists approach treatment.

The Surprising Findings

Dr. John J. Zhang and colleagues conducted a cohort study of 250 women aged 18-38 undergoing their first IVF treatment. Their research, published in the International Journal of Gynecology and Obstetrics, discovered that the cumulative live birth rate over six months showed no significant difference between women with low (1-2), intermediate (3-6), or high (7 or more) numbers of mature eggs retrieved—58.8%, 55.7%, and 62.8% respectively.

"Our findings indicate that aggressive ovarian stimulation and retrieval of large cohorts of oocytes do not necessarily benefit the patient clinically," the researchers concluded.

Perhaps most striking was the inverse relationship between egg efficiency and quantity. The study found that women who produced fewer eggs had remarkably higher utilization rates, with 38.5% of eggs in the low-yield group resulting in live births compared to just 4.9% in the high-yield group.

The implantation rate based on the number of blastocysts transferred for each group was highest for women with a low metaphase II oocyte yield (84.6%), followed by those with an intermediate yield (56.9%), and lowest in the high-yield group (42.2%).

This suggests that aggressive ovarian stimulation protocols designed to produce large quantities of eggs may lead to significant "oocyte wastage" without improving clinical outcomes. Current IVF practices often prioritize maximizing egg retrieval, but these findings challenge that approach.

Contrasting Research

A comprehensive study by Dr. Ryan G. Steward and colleagues, published in Fertility and Sterility, offers important counterpoints. Their analysis of 256,381 IVF cycles from the Society for Assisted Reproductive Technology national registry revealed that live birth rates increased steadily up to 15 oocytes retrieved, then plateaued.

According to their findings, "The LB [live birth] rate increased up to 15 oocytes, then plateaued (0–5: 17%, 6–10: 31.7%; 11–15: 39.3%; 16–20: 42.7%; 21–25: 43.8%; and >25 oocytes: 41.8%)."

However, Steward's team also found that the rate of ovarian hyperstimulation syndrome (OHSS), a potentially serious complication of fertility treatments, increased dramatically after 15 oocytes were retrieved. Their data showed OHSS rates of 0.09% with 0-5 oocytes, 0.37% with 6-10 oocytes, 0.93% with 11-15 oocytes, and rising dramatically to 6.34% with more than 25 oocytes.

"Retrieval of >15 oocytes significantly increases OHSS risk without improving LB rate in fresh autologous IVF cycles," they concluded.

Mild Stimulation Approach

Further evidence comes from a meta-analysis published in Human Reproduction Update, which investigated whether retrieving a low number of oocytes following mild ovarian stimulation is associated with impaired implantation rates.

This analysis of three randomized controlled trials found that the optimal number of retrieved oocytes depends on the stimulation protocol used. Optimal embryo implantation rates were observed with just 5 oocytes retrieved following mild stimulation (31%) versus 10 oocytes following conventional stimulation (29%).

The researchers concluded, "After mild ovarian stimulation, a modest number of oocytes is associated with optimal implantation rates and does not reflect a poor ovarian response. Therefore, the fear of reducing the number of oocytes retrieved following mild ovarian stimulation appears to be unjustified."

Explaining the Paradox

Why might fewer eggs sometimes work better? Zhang's team suggests several possible explanations. The high estrogen levels resulting from aggressive ovarian stimulation may negatively impact embryo quality and endometrial receptivity.

Dr. Zaher Merhi, co-author of the Zhang study, notes that the biological quality of eggs may be compromised when large numbers are produced.

Steward and colleagues suggest that "very aggressive ovarian stimulation regimens are no longer justified as a means to increase oocyte yield in fresh cycles, especially in good-prognosis patients." They point out that harvesting more than 15 oocytes "does not necessarily increase the number of live babies born yet considerably inflates the incidence of clinically significant OHSS and the extreme morbidity that comes with it."

Finding Balance in Clinical Practice

This research has significant implications for patients considering IVF treatments, particularly those concerned about the physical and financial costs of aggressive stimulation protocols. It also raises questions about the growing trend of oocyte cryopreservation (egg freezing) for fertility preservation or family planning purposes. More personalized approaches are needed. 

As fertility clinics increasingly offer egg freezing services, understanding the reproductive potential of each egg becomes crucial. For younger women with normal ovarian reserve, perhaps retrieving fewer eggs using gentler stimulation protocols might be equally effective while reducing potential side effects and costs. For older women, this shows low oocytes might not mean low success rate.

Looking Forward

The Zhang study's authors suggest future research should evaluate whether gentler ovarian stimulation might reduce the "oocyte wastage" observed in conventional IVF.

Dr. Merhi concludes: "Whether oocytes produced from a low ovarian response are biologically more effective than oocytes obtained from a high ovarian response remains to be determined."

For patients and practitioners alike, this research opens important conversations about treatment optimization. While the debate continues, one thing appears clear from these studies: in IVF, the quality of eggs may matter just as much—if not more—than quantity.

As the field evolves, this paradigm shift could lead to less aggressive, more patient-friendly treatment protocols that maintain or improve success rates while reducing physical, emotional, and financial burdens on patients seeking to build their families.