A strong dogma hovers over fertility studies in females. For more than half a century, it was thought that women are born with a set number of eggs and these diminish over the years. When all the eggs run out, menopause as we know it sets in heralded by hot flushes, mood swings, weight gain and the rest. Science, which always tells the truth and nothing but the truth, affirms the converse: the presence of oogonial stem cells sliced the long held finite egg theory.
Unescapable death of eggs
At birth, women possess over two million eggs within their ovaries and approximately eleven thousand meet a non-bloody end every month before puberty. During her teenage years, a girl has only three thousand of the initial 2 million eggs. From this point on, every month, close to 1000 eggs are sacrificed irrespective of nutritional supplementation, contraceptive pills and pregnancy. When the last egg is exhausted, production of estrogen ceases and menopause sets in. Inequitably, men don’t possess a similar time bomb to blast off fertility.
Understanding biological clock
All eggs stored in the dormant stage undergo activation. An activated egg commences on the maturation process (approximately 3 months) to produce an egg capable of ovulating. The signal which triggers the activation and ovary ‘suicide’ remains unknown.
Every egg present within the ovaries is protected by a resting follicle. 30-35 resting eggs embark on the 85 day development which culminates in ovulation. On reaching ovulation stage, the follicle transforms to corpus luteum. Corpus luteum secretes progesterone. Egg ovulation accelerates when a woman reaches 37-38 years. A steep decline of remaining follicles sets in. Owing to the diminished number of resting eggs in the follicle, the number activated to ovulate, decreases dramatically.
Does it mean that women run out of eggs?
Mammalian ovaries are highly differentiated and more complicated than they were previously conceptualized. The presence of stem cells within the oocyte has opened new doors. Now, the prospect of growing unlimited human oocytes is a theoretical possibility. Such lab-bred oocytes can be used in IVF or a source for embryonic stem cells. Although, the current belief is that women run out of 90 percent eggs by the time they reach 30’s, the ability for a woman to continuously grow and replenish eggs is biologically possible. If men have such a replenishing resource, there is no reason why women should not possess something similar.
But, a catch here is that egg stem cells form less than one percent of the total ovarian population.
In conclusion, the conception that women have an inbuilt biological clock stems from the fact that ovarian function declines with advancement in age not because of the steady dwindling in the number of follicles, but from the inability of the stem cells to get activated. If fertility of a woman is discussed purely in terms of the ability to conceive, she can after the age of 40 through ART techniques, frozen embryo and IVF. These processes use cryopreservation and this is available at low rates.