At puberty, a woman begins to ovulate.
Ovulation is the release of a mature fertilizable egg from the ovary.
Ovulation should continue throughout a woman’s reproductive lifespan typically at regular monthly intervals.
At each of the two ends of the reproductive lifespan, after the onset of puberty and prior to menopause,
menstrual cycle intervals may be irregular and generally longer in duration.
(Available Drawing: Female Puberty)
A woman has an estimated 300 to 400 thousand eggs contained within her ovaries at the time of puberty.
She is usually presumed to have no remaining eggs at menopause, although research has recently demonstrated
that she may actually have a few hundred (or thousand) eggs remaining at menopause. Since a normal
reproductive lifespan typically covers the ages 14 to 44 there are about 30 years of ovulation with about
12 ovulations per year for a total of about 300 to 400 ovulations. Thus, a woman "uses up" an average of
about 1000 eggs per menstrual cycle (300 to 400 thousand eggs in 300 to 400 ovulations).
(Available Drawing: Female Reproductive Lifespan)
The primary purpose of the hormonal evaluation assessing "ovarian reserve" is to (roughly) determine the
number of eggs remaining within the ovaries. Two women each 35 years old may have very different ovarian reserves.
If one woman has used her eggs rapidly (more than 1000 per cycle) then she may have a reduced ovarian reserve
while another woman who has used her eggs slowly (less than 1000 per cycle) may have a good ovarian reserve.
It is not clear whether these eggs are used at a uniform rate over the entire reproductive years or whether
there is a certain time period of rapid loss. It does appear that about 10-15 years prior to menopause
(at about the age 37-38 and continuing for up to a few years) there is a period of accelerated loss of follicles
with an initial shortening of the egg maturing phase of the menstrual cycle (follicular phase).
This period of accelerated loss does not fully account for the enormous loss of eggs during the reproductive lifespan.
A follicle is a cyst in the ovary containing an egg. Most likely, of the 1000 eggs that are committed for any
given cycle only a small number of follicles (maybe 5-25) actually begin the process of maturation at the onset of the cycle.
Ovulation can be interrupted by physiologic events (such as during pregnancy or breast feeding), medication
(such as oral contraceptive pills), or pathology (such as hormonal or anatomic abnormalities).
Available Case Reports: