The ovarian reserve is the ovary’s capacity to produce eggs or oocytes which can be fertilised. Throughout a woman’s life, the ovarian reserve decreases. Surprisingly, at 28 weeks of gestation, the female foetus has between 6 and 7 million immature eggs. When a baby girl is born, it is estimated that she has approximately 2 million eggs. At puberty, she has approximately 500,000 left and around 25,000 between the ages of 38 to 51, the average age of menopause when egg loss accelerates until the ovaries stop working altogether.
The big question is why is the ovarian reserve used up over a woman’s lifetime? Fertility is evidently determined by a biological clock that marks the deterioration of eggs and their quality, but how does it work?
Recent studies have shown that when a breakage occurs somewhere in the egg’s double helix of DNA (genetic information) -a common occurrence in eggs- as the egg ages, there are increasingly fewer mechanisms for repairing the damage (Titus and colleagues at the New York Medical College in Rye, New York). In more everyday terms, proteins are responsible for repairing internal mechanisms of the eggs and they become increasingly inefficient with age. A damaged egg is not able to be fertilised and, as it is not healthy, the egg programmes its own death (apoptosis) and disappears. Therefore, the decrease of the ovarian reserve is two-fold, affecting both the quality and quantity of eggs in the ovaries.
These new studies show that different genes exist for repairing the oocyte and that if the mechanism does not work properly, the ovarian reserve is used up prematurely and there is nothing we can do about it. Maybe when research produces advances we will be able to stop this depletion, although it doesn’t look like it will happen any time in the near future.
One of the best decisions women of childbearing age can make is to preserve their fertility through egg vitrification, which freezes their eggs, enabling them to choose the most appropriate time to have a baby. In fertility clinics, experts in assisted reproduction can advise women about the technique of cryopreservation for preserving their eggs. It is also recommended for women who have endometriosis or cancer.