Diminished Ovarian Reserve (DOR) is a common diagnosis in reproductive medicine, referring to a lower-than-expected quantity and quality of eggs remaining in the ovaries for a woman’s age. This condition signals a reduction in a woman’s reproductive potential and can make achieving pregnancy more difficult. Understanding the biological basis of this decline, the factors that contribute to it, how it is diagnosed, and the available treatment options is a crucial first step for anyone navigating this fertility challenge.
Understanding Ovarian Reserve and Its Decline
A woman is born with a finite supply of primordial follicles, which constitute her ovarian reserve. At birth, the ovaries contain between one and two million eggs, a number that drastically declines to about 300,000 to 400,000 by the time of puberty.
The decline in this reserve is a continuous, natural process, entirely independent of factors like contraception, pregnancy, or menstrual cycles. Throughout the reproductive years, thousands of follicles are lost each month through a process called atresia, with only a select few developing to the point of ovulation. This depletion rate is generally slow until a woman reaches her mid-to-late thirties, at which point the rate of loss increases significantly.
Diminished Ovarian Reserve occurs when this natural decline happens sooner or more rapidly than typically seen for a woman’s chronological age. Biologically, DOR means the supply of primordial follicles is lower than expected. The reduced number of follicles also often coincides with a decline in the overall quality of the remaining eggs, which further affects fertility potential.
Factors Contributing to Diminished Ovarian Reserve
Advanced reproductive age is the most common factor leading to DOR, as the rate of egg loss accelerates after the age of 35. This chronological aging is a major predictor of both the number and quality of remaining eggs. However, DOR can also affect younger women due to a variety of other causes.
Genetic predispositions, such as the FMR1 gene pre-mutation associated with Fragile X syndrome, can lead to a premature decline in the ovarian reserve. Aggressive medical treatments like chemotherapy or radiation therapy can be highly toxic to the ovarian follicles, causing widespread and rapid destruction of the egg supply. Previous surgical interventions on the ovaries, such as those to remove large endometriomas or ovarian cysts, can inadvertently remove or damage healthy ovarian tissue.
Autoimmune disorders may target the ovaries and contribute to diminished reserve. Furthermore, lifestyle factors like tobacco use and smoking are specifically associated with an accelerated decrease in ovarian reserve. In many cases, however, no clear cause can be identified for the condition, which is then classified as idiopathic DOR.
How Diminished Ovarian Reserve is Diagnosed
A diagnosis of DOR is established through a combination of blood tests and specialized ultrasound imaging. The Anti-Müllerian Hormone (AMH) test is one of the most widely used blood tests, as AMH is secreted by the small follicles in the ovaries.
AMH levels correlate strongly with the number of remaining follicles and can be drawn at any point in the menstrual cycle. A low AMH level, often below 1.0 nanogram per milliliter (ng/mL) in severe cases, is indicative of a diminished ovarian reserve. The lower the AMH level, the fewer follicles are available to be stimulated during fertility treatments.
Another blood test measures the Follicle-Stimulating Hormone (FSH), typically performed on day two or three of the menstrual cycle. A high FSH level, generally over 10 mIU/mL, suggests that the pituitary gland is working harder than normal to stimulate the ovaries. High FSH levels often accompany low AMH levels in DOR patients.
The third main diagnostic tool is the Antral Follicle Count (AFC), which is an ultrasound measurement conducted early in the menstrual cycle. The AFC involves counting the number of small, fluid-filled sacs, or antral follicles, measuring two to ten millimeters in diameter within both ovaries. A low AFC, with a total count often between three and ten, indicates a reduced number of recruitable follicles and is highly correlated with low AMH levels.
Navigating Fertility Treatment Options with DOR
A diagnosis of diminished ovarian reserve does not eliminate the possibility of pregnancy, but it does mean that fertility treatments may need to be modified. For many individuals with DOR, In Vitro Fertilization (IVF) is the most effective treatment option. IVF protocols for these patients often involve higher doses of ovarian stimulation medication to maximize the number of eggs retrieved in a single cycle.
While the success rates for IVF with a woman’s own eggs may be lower compared to women with a normal reserve, age remains a more significant factor in determining egg quality and subsequent pregnancy success. Egg freezing can also be an option for women with DOR who wish to preserve their remaining reproductive potential before the decline progresses further.
When IVF with a woman’s own eggs is unsuccessful, the use of donor eggs offers a very high chance of conception. Donor eggs come from younger women. The donor eggs are fertilized with the partner’s sperm, and the resulting embryo is transferred into the recipient’s uterus, allowing her to carry the pregnancy.