Causes and risk factors of poor ovarian reserve

Poor ovarian reserve is a clinical condition in which the ovaries contain a fewer number of oocytes (eggs) as expected for that particular age of a woman. Women are born with 1 to 2 million oocytes in their ovaries which rapidly declines, reaching 5 lakh oocytes at puberty. Out of these, only about 400 oocytes ovulate and are potential of giving a pregnancy. The Rest of the oocytes regress and are lost. The rate of loss is genetically predetermined. Most women will experience a significant decline in the number of their oocytes in their forties, while others may experience this much earlier. Those women who experience premature decline are considered to have diminished ovarian reserve or poor ovarian reserve. Although genetic factors are a major cause of poor ovarian reserve, this diminishes may happen because of other reasons also.

1. Age: Natural decline in ovarian reserve is observed as age advances. Decline starts after age 32 and accelerates after age 35.

2. Cigarette smoking and Alcohol: has been proved to accelerate ovarian ageing and has a negative impact on fertility.

3. Genetic abnormalities: Fragile X and other X chromosome abnormalities. Approximately 20 to 25% of women with Fragile X syndrome experience primary ovarian failure and approximately 25% experience early diminished ovarian failure.

4. Radiotherapy and Chemotherapy: For various cancer treatments reduce ovarian reserve by causing damage to germ cells.

5. Ovarian surgery: such as for endometriosis, adenomas and other ovarian benign and malignant tumours. During excision of these tumours, some amount of normal ovarian tissue may be lost causing poor ovarian reserve.

6. Idiopathic: This means that there is no apparent cause that accounts for nearly 50% of cases with poor ovarian reserve.

7. Autoimmune diseases in which antibodies are produced against their own cells.

8. Adrenal gland impairment.

9. Iatrogenic, e.g., due to radiation, chemotherapy or surgery, such as laserization of the surface of the ovary to treat endometriosis. Excessive laparoscopic ovarian drilling for PCOS, Uterine artery embolization for fibroids has been reported to cause premature ovarian failure.

10. Genital Infections: Tuberculosis, Herpes Simplex virus, Chlamydial infections also cause poor ovarian reserve.

11. Lifestyle factors like dietary habits, lack of exercise, obesity may also have a role to play.

The diminished ovarian reserve does not eliminate the possibility of pregnancy. However, this problem should encourage a woman to be more aggressive in her quest to become pregnant as time is clearly of the essence. Early detection and active management are essential to minimize the need for egg donation in these women.