An analysis of 14,420 eggs from 1,856 ICSI cycles found that age had the most consistent association with development and embryo chromosome status. Associations with endometriosis and body weight depended on the outcome measured. An AI egg score showed some predictive value, but its additional contribution was limited.
What affects egg quality most: weight, endometriosis, a hormonal condition such as polycystic ovarian disease, or age? The question comes up frequently in fertility care. In this analysis, age was the factor most consistently associated with egg and embryo development. Some outcomes were less favorable in particular patient groups, but the pattern was not the same across all measures. The study also explored what an AI assessment of an egg image might add.
Age showed the most consistent association
Researchers in São Paulo, Brazil, and Canada examined 1,856 intracytoplasmic sperm injection (ICSI) cycles performed between 2020 and 2025. They compared outcomes for 14,420 oocytes, considering endometriosis, overweight, obesity and polycystic ovarian conditions. They also compared women younger than 38 with those aged 38 or older.
In older women, AI scores for eggs and developmental scores for embryos were lower, and a smaller proportion of fertilized eggs tended to reach the blastocyst stage. The proportion of chromosomally normal embryos and cumulative pregnancy rates were also lower. A blastocyst is an embryo at a stage usually reached around five to six days after fertilization. The findings link age to several stages of development as well as to pregnancy outcomes.
Do endometriosis and obesity always predict poorer eggs?
Endometriosis involves tissue similar to the uterine lining growing outside the uterus. Inflammation and changes in ovarian function are possible routes through which it may affect fertility. Obesity can influence the hormonal and metabolic environment. Neither condition, however, was associated with consistently poorer results across every embryological and clinical measure in this study.
The overweight group showed less favorable associations for good-quality blastocyst formation and cumulative reproductive outcomes. That does not establish that being overweight is more harmful to eggs than obesity. Patient characteristics, disease severity, metabolic status and treatment conditions may influence comparisons.
Women with polycystic ovarian conditions had relatively more mature eggs, and laboratory measures of embryo development were generally preserved. Observed cumulative pregnancy rates were also higher. This cannot establish that such conditions confer a fertility advantage. Different factors may relate to egg and embryo development in different ways.
What could the AI score predict?
MAGENTA analyzes microscopic images of eggs and assigns a score related to their developmental potential. Appearance and maturity can provide clues, but they cannot reliably determine which egg will fertilize normally and ultimately result in a healthy baby.
Higher MAGENTA scores were associated with more favorable fertilization and blastocyst outcomes. The reported odds ratios were 1.53 for fertilization, 1.67 for blastocyst formation and 1.26 for formation of a good-quality blastocyst. These are odds ratios. They do not mean the fertilization or blastocyst formation rates increased by 53% or 67%.
Adding the AI score to existing clinical variables yielded only a limited improvement in predictive accuracy. It might serve as an additional assessment tool, but the score alone cannot determine whether fertilization or pregnancy will succeed.
Why one number cannot define egg quality
An egg can fertilize normally and still stop developing. A well-formed blastocyst can have a chromosome abnormality, while an embryo with a less favorable appearance can lead to pregnancy and birth. Fertilization and blastocyst rates describe different stages from live birth.
This was a retrospective observational analysis. It could identify associations between age, weight, disease and developmental outcomes, but could not show that one factor directly reduced egg quality. Endometriosis and obesity may still matter through ovulation, implantation and pregnancy complications as well as through effects on eggs.
Interpreting age in an individual assessment
The findings reinforce the importance of age in fertility care. Outcomes can still vary substantially among women of the same age according to ovarian reserve, egg number, underlying conditions, sperm factors and prior treatment results. A broader assessment is more informative than attributing a concern about egg quality to weight or one diagnosis alone.
AI may help refine estimates of developmental potential. Whether its use improves pregnancy or live-birth rates needs to be tested. Among the factors examined here, maternal age was the most consistently associated with development and pregnancy outcomes, a consideration when discussing treatment timing and individual options.
Source: Fertgroup and Instituto Sapientiae, São Paulo, Brazil, with Future Fertility Inc., Canada. “Revisiting common female infertility factors traditionally associated with impaired oocyte quality: insights from IVF outcomes and AI-derived oocyte score performance.” Frontiers in Endocrinology, published online November 4, 2026. DOI: 10.3389/fendo.2026.1957168.
Related reading: Why AMH alone cannot predict egg yield: 2,162 IVF cycles.
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