My memory of school biology is fading fast so perhaps someone can answer a couple of questions for me…
If I remember correctly, women are born with all the ova they will ever produce.
Approximately how many are present in the ovaries at birth?
Is this quantity proportional to the length of a woman’s fertile period?
Is the full supply of ova exhausted through the woman’s fertile period or are many ‘wasted’?
From these lecture notes on human biology:
From “Robbins Pathologic Basis of Disease” (5th edition):
“During fetal development, ovaries contain as many as 7 million oocytes. The oocytes begin to disappear in utero, however, so that by birth there are about 3 million left, and by menarche their numbers have already dwindled to a mere 400,000. Further loss continues after puberty, and when menopause occurs fewer than 10,000 remain.”
Although a woman normally ovulates only one egg during each menstrual cycle, multiple ova actually begin the maturation process each month, only to arrest and die. There’s a LOT of waste (or perhaps selection favoring only the best quality oocytes?).
I don’t know whether the initial number of oocytes at birth has any direct correlation with the length of a woman’s fertile period. I rather doubt it, though, and suspect that the rate at which the eggs are used up is more important - perhaps women who go into menopause earlier have more ova start the development process each month, so they use up their supply faster.
Thanks Darwin’s Finch & Artemis
Follow-up question…
What happens when a woman takes a contraceptive pill continually from one cycle to the next in order to avoid menstruation (effectively preventing ovulation)? Are the eggs that would normally be produced lost or simply withheld and does/could this have any effect on the woman’s fertile life-span?
IIRC, the hormones in contraceptive pills make the body act as though it’s already pregnant. Ova are released, but even if they’re fertilized, they find no purchase in the uterus once they get there.
Just being pedantic here.
Isn’t that ‘in utero’ phrase wrong there? Wouldn’t they disappear in the ovaries?
Ok, I thought that the pill actually prevented ovulation itself. If what you are saying is correct (that the body is tricked into believing that it is pregnant), then why would menstruation occur at the end of each monthly course of the pill?
In any event I’m interested in the effects (if any) of taking the pill continuously ‘back-to-back’ without a break for menstruation (rather than the prescribed course of 28 days followed by a break).
The pill makes the body think it’s pregnant, which usually includes suppressing ovulation entirely. (I don’t know what effect that has on oocyte population levels.) If the occasional egg makes it out, the pill also prevents implantation in the uterus, but I think that’s relatively rare.
The New Yorker ran an interesting article about three years ago about the person who developed the Pill, back in the fifties. (Interestingly, he was a devout Catholic who thought he was creating a form of birth control that’d be acceptable to the Church.) It also discussed how the 21 days on-pill, 7 days off-pill (or taking sugar pills) cycle was set up - they were trying to recreate what they saw as normal, rather than trying to do something for medical reasons. (It then goes on to discuss how women in medically primitive cultures, who are usually pregnant or constantly breastfeeding, don’t have their periods very often, averaging maybe one a year.) The article posited that there was no medical reason not to suppress menstruation most of the time, and that there were probably benefits with regard to breast cancer. I can’t find the article to link to it, I’m sorry.
The question’s been answered, but it should be noted that Cecil answered it: Does use of The Pill delay menopause? and contradicted one of the things posted to this thread.
What was meant was that the oocytes of a female start to disappear before the female is born.
Being a pill taker for the past 15 years I have some thoughts…
I’m not sure that it is right saying thatyour body is acting as if it’s already pregnant…if you were ‘tricking’ your body into thinking
that, then surely you would have other symptoms of pregnancy! I have been told by various doctors and read various leaflets that come with the pill in the box saying that you do not ovulate, which I take that to mean you do not release an egg.
So it seems will still don’t have a concise answer as to where do the eggs go?
When you take a pill for 21 days…then stop for 7 days as is usual, when you bleed in that time that is NOT effectively a period, you are not ovulating…it is a ‘fake’ period, you are just bleeding as a withdrawl from the pill. When you take the pill continuously for 28 days and then start on a pack for another 28 days straight after obviously you do not bleed. All that’s stopping the bleeding is the pill taking, you are not ovulating at this time at all. Doctors say that there is no medical benefit for a woman to have the 7 day break, however women like too, as a test to see if they are preganant, as if they don’t bleed they are often
pregnant (although not always, there are many reported case of pregnat women contining to have ‘periods’ or some bleeding while pregnant).
Gila B, my apologies, I was busy posting my reply, when yours came in, indeed we seem to agree over the lack of benefits to a women to have a ‘fake’ period.
Yes, but they’re disappearing in the ovaries that are in the baby that’s still in the uterus, so it’s still in utero.
minkmuff,
the swollen, tender breasts, the increased appetite, the morning nausea…all side effects i’ve had on the pill…
but it’s from the hormone levels, mimicing a day 21 peak, not a pregnancy.
Wow, double-recursive-utero-overy-oocyte-nullification.
I think I have a headache.