What is a Diminished Ovarian Reserve (DOR)?
A woman’s ovarian reserve refers to the number (quantity) and/or quality of eggs (oocytes) that she has remaining in her ovaries. Diminished ovarian reserve (DOR) refers to a reduced number and/or quality of eggs in the ovaries.
A woman’s eggs are produced during fetal development, so women are born with all of the eggs that they will ever have (roughly 1-2 million). There is no scientific evidence that supports eggs being produced after birth. But ovarian reserve naturally declines over time, and it’s estimated that only 300,000-500,000 eggs remain in the ovaries by the time a woman reaches puberty and less than 1,000 eggs remain by the time she reaches menopause. A rapid decline in ovarian reserve is observed after 35 years of age, which is also when there is a decline in the quality of a woman’s eggs in her ovaries. However, it’s possible to see DOR in women under 36, as well, such as in cases of women with primary ovarian insufficiency.
Why does ovarian reserve decline over time?
The majority of ovarian reserve decline is due to a process known as apoptosis (also called atresia), or programmed cell death. It is known that some eggs naturally degenerate during each menstrual cycle, which allows for one (sometimes two) egg to mature and be expelled from the ovary in a process known as ovulation. In some cases, medical treatments (such as chemotherapy) or conditions (such as endometriosis) can reduce ovarian reserve. Increased exposure to toxins such as arsenic, pesticides, and BPA have also been shown to reduce ovarian reserve. Other factors that may contribute to DOR include obesity, autoimmune diseases, oxidative stress, hormonal imbalances, and certain medications.
How is DOR diagnosed?
DOR is normally diagnosed through blood and ultrasound screening. The following are signs of DOR:
Elevated blood level of the hormone FSH (follicle stimulating hormone) at the beginning of the menstrual cycle
Low blood level of AMH (anti-Müllerian hormone)
A low antral follicle count (the number of follicles viewed on an ultrasound at the beginning of the menstrual cycle)
These tests can predict a woman’s ovarian reserve and response to IVF medications. They cannot determine the quality of the eggs in the ovaries.
Why is DOR a problem?
As women age, the quality of their eggs declines. In particular, there is an increased chance of their eggs having chromosomal abnormalities (the wrong amount of DNA). This can affect fertilization, embryo development, and pregnancy outcomes, making DOR a common cause of infertility.
Can DOR be treated?
Unfortunately, DOR cannot be reversed or treated, and women with DOR often require multiple rounds of IVF in order to conceive a pregnancy. This may be circumvented if a woman chooses to freeze her eggs at a younger age for future IVF.
Sources:
Age-Related Fertility Decline - StatPearls - NCBI Bookshelf (nih.gov)
