Uterine Ageing, Not Egg Quality, Limits Older Women's Fertility Success

A recent study highlights that the capacity of the uterus, not the age of donor eggs, is the critical element affecting successful pregnancies in women over 40. This finding emerges from analysis of over 50,000 IVF cycles conducted in Spain, one of the few European nations permitting anonymous egg donation and maintaining a centralised registry.

Historically, fertility treatments for older women have focused heavily on egg quality. However, this research, published in the journal JAMA, suggests a biological 'ceiling' for the uterus at approximately 44 years of age, regardless of the egg's viability. After this point, the likelihood of a live birth using donor eggs declines significantly, dropping from a 30% success rate at 44 to 24% at 45, and just 11% by 49.

Professor Nick Macklon, Medical Director at London Women's Clinic, commented on the findings, noting that while the study aligns with clinical experience, it presents a larger dataset than previously available. Dr. Simon Fishel, founder of CARE Fertility, emphasised that the research pinpoints the uterus as the limiting factor, rather than a broad assumption about egg quality. He described this as a significant step forward for reproductive medicine.

The study's authors propose that age-related changes in the uterine lining, such as increased inflammation, could be responsible for this observed decline. This insight opens avenues for future treatments aimed at improving uterine receptivity, potentially through anti-inflammatory drugs or other interventions, which could extend the period of fertility for women beyond current limits.