Women's fertility declines with age even when using donor eggs, suggesting the problem lies not in egg quality but in changes to the uterus itself, researchers have found.
Studies show that women over 40 have lower pregnancy success rates with donor eggs compared to younger recipients, despite receiving eggs from young, healthy donors. This pattern points to age-related deterioration in the endometrium, the tissue lining the womb that must prepare for embryo implantation.
Dr. Navid Ekteshami and colleagues at fertility clinics have documented how endometrial function changes with age. The lining becomes thinner, develops fewer blood vessels, and produces fewer of the proteins needed to support early pregnancy. These changes happen gradually and accumulate over time, creating what experts describe as a "hidden fertility ceiling" that donor eggs alone cannot overcome.
The endometrium's decline explains a puzzling clinical observation: a 45-year-old woman using her own eggs faces poor odds, but a 25-year-old using the same woman's eggs faces better odds. Neither the younger woman's age nor the older woman's age matters. What matters is the age of the uterus.
Current fertility treatments cannot reverse these endometrial changes. Standard hormone therapies boost the lining's thickness temporarily but do not restore its underlying cellular function or blood flow. Doctors typically adjust medication doses and embryo transfer timing, but these adjustments offer only modest improvements.
Researchers are exploring new approaches. Studies examine whether low-dose aspirin, testosterone patches, or growth factors can improve endometrial health in older women. Some fertility clinics test endometrial receptivity before transferring embryos, identifying windows when the tissue is most hospitable to implantation.
The findings reshape conversations about fertility preservation and aging. Women cannot simply delay childbearing and expect donor eggs to eliminate age-related risks. The