Low ovarian reserve (LOR), sometimes referred to as diminished ovarian reserve, signifies that a woman has a reduced number or quality of eggs in her ovaries compared to what is expected for her age. This condition indicates a diminished reproductive potential, which can make it more challenging to conceive. While it does not always prevent pregnancy, LOR is a significant factor affecting fertility.
The Role of Age
A woman’s age is consistently recognized as the most common and influential factor contributing to low ovarian reserve. Women are born with a finite number of eggs, or primordial follicles, a supply that cannot be replenished. This pool of eggs naturally declines throughout a woman’s life, with the most significant decreases typically occurring after the mid-30s.
The process of ovarian aging involves a gradual reduction in both the quantity and the quality of eggs. While the number of eggs steadily decreases over time, egg quality also diminishes, particularly after age 35. This decline in quality often involves an increased likelihood of genetic abnormalities, such as aneuploidy, in the eggs. Consequently, older eggs may have a reduced capacity for successful fertilization and healthy embryo development.
Genetic and Chromosomal Factors
Beyond the natural aging process, certain genetic and chromosomal factors can predispose individuals to low ovarian reserve. Conditions like Fragile X syndrome pre-mutation (FXPM) affect ovarian function. Women who carry the FXPM, an alteration in the FMR1 gene, may experience accelerated depletion of their ovarian follicle pool, leading to LOR or even premature ovarian insufficiency (POI).
Another genetic consideration is Turner Syndrome, a chromosomal condition where females have only one X chromosome instead of the usual two, or a mosaic form where some cells have the anomaly. This genetic difference often results in abnormal ovarian development, leading to a reduced number of eggs from birth or accelerated follicle loss, contributing to low ovarian reserve. When LOR, especially POI, has a genetic basis, ovarian function may cease before age 40.
Impact of Medical Treatments
Medical interventions can directly contribute to low ovarian reserve by damaging ovarian tissue or depleting the egg supply. Chemotherapy and radiation therapy, commonly used in cancer treatment, are harmful to ovarian function. These treatments can destroy ovarian follicles, leading to a significant reduction in a woman’s egg reserve, sometimes resulting in premature ovarian insufficiency.
Surgical procedures involving the ovaries can also affect ovarian reserve. Operations for conditions like endometriosis, ovarian cysts, or the removal of one ovary can remove or damage healthy ovarian tissue. The impact depends on the surgery’s nature and invasiveness, but any procedure reducing ovarian tissue volume can diminish the egg supply.
Other Contributing Influences
Various other factors can diminish ovarian reserve. Certain autoimmune conditions can cause the body’s immune system to attack ovarian tissue. This autoimmune response can cause inflammation and damage, accelerating follicle loss and contributing to conditions like autoimmune oophoritis, linked to premature ovarian insufficiency.
Lifestyle choices also play a role, with smoking being a well-established factor accelerating ovarian aging. The chemicals in cigarette smoke have a toxic effect on ovarian follicles, leading to their premature depletion. While research is ongoing, exposure to certain environmental toxins, such as pesticides or industrial chemicals that disrupt endocrine function, may affect ovarian health and contribute to declining egg reserve.
Endometriosis or recurrent pelvic inflammatory disease (PID) can damage the ovaries. Endometriomas, or “chocolate cysts,” on the ovaries can destroy healthy ovarian tissue. Chronic inflammation and scarring from PID can impair ovarian function and reduce viable eggs.
Unexplained Low Ovarian Reserve
Despite thorough medical investigation, a percentage of low ovarian reserve cases lack an identifiable cause. In these instances, the condition is termed idiopathic, meaning its origin is unknown. This can be frustrating, highlighting the complex nature of reproductive biology.
Even with advancements in diagnostic techniques, the underlying reasons for LOR in these unexplained cases are not understood. Ongoing research aims to uncover the mechanisms and factors that contribute to this idiopathic form of diminished ovarian reserve, to provide more comprehensive answers and potential interventions.