Math Question re:20%

BillyHorrible

I am crap at math, and even worse with statistics and probability.  So can someone help me with something?

I know the oft repeated phrase is that a healthy couple has a 20% chance each cycle.  But is that based on a single sex act?  Or is it based on averaging the number of times an average person has sex in a cycle?   Would the probability increase if you have sex more often?  I remember something about flipping pennies from elementary school not changing the probability of heads v. tails, but this isn't a discrete event like that since the sperm can remain viable for several days.

BillyHorrible

GhostMonkey said:

That is the best chance you have in a cycle with perfect timing and zero fertility issues. It goes down from there. I you have sex 2 days before ovulation and no other time or you have sex twice every day the whole month, you have the exact same chances.

So theoretically, in a perfect world, where you got a post it note from ThePowersThatBe saying "Ovulation will occur on Tuesday" there would be no incentive (other than good sex) to having sex any day but Tuesday?

GhostMonkey said:

The major drop is still considered the be at 35, though some research is showing it isn't as drastic as previously though and 40 is a bigger drop off than 35.

This is interesting to me.  And I wonder if it's an evolutionary thing given that we are living longer and having babies later as opposed to our biological ancestors who were having babies at 12 and dead by 35.

holliberry28

I just started watching the Great Sperm Race, after it was recommended by @DarcyHermione, and it is pretty fucking interesting.  Thanks Darcy

BillyHorrible

estoyborracha said:

I doubt it has much to do with evolution. Life expectancy really wasn't that much different 100 years ago than it is today, it just seems that way because infant mortality is down.

I'm not trying to start something, because I love this kind of stuff, and I'm loving this discussion, but I'm not talking about Jane the medieval miller's daughter type of ancestor. I mean "Uggh" and "Gnuh," our early homo-erectus/homosapien type of ancestor.

BillyHorrible

littleliverpill said:

I'm not sure if that supports or contradicts the idea that, as @GhostMonkey said, "If you have sex 2 days before ovulation and no other time or you have sex twice every day the whole month, you have the exact same chances" because I'm not certain whether FF is implying that more sex = more chances of hitting O-2 (or whatever day gives the highest probability of conception) or just more sex = more sperm = better chances of conception.

Yeah, I think the big issue is that you can't predict ovulation to the date.  So if you were to just have sex once between your period and when you end up ovulating you have more of a chance of missing that egg than if you have sex multiple times.  I think that's a different issue than the 20% one.  But I could be misreading it.

URMySunshine77

GhostMonkey said:

estoyborracha said:

I doubt it has much to do with evolution. Life expectancy really wasn't that much different 100 years ago than it is today, it just seems that way because infant mortality is down. Also, women today are fertile earlier than in previous generations - having first menses around age 9 rather than 14 - likely because of hormones and changes in nutrition. Not that any of that is useful or relevant to your original question in any way.

Even when adjusted for infant deaths, the age only goes up about 5 years. It's not like it jumps from 47 to 90. It goes from 47 to 52.

And getting your period sooner does not make you physically ready to bear children sooner. For those that start before age 12, at best 50% of their cycles are ovulatory.

Thanks for asking this, @BillyHorrible. It's something I've considered often.

@Ghostmonkey: Do you think that women who start menses later might be more fertile when advanced maternal age starts? I started my period at 15 and I'm 37. I've hoped that starting my period later might give me more eggs to work with at this point.

pibsquared

I have wondered the same thing URMySunshine77. I have heard no, but I have not looked up anything about it, I would be interesting in seeing the research though.

On the whole existence and the chances of our lives. My sister sent this article to me, thought those interested in the probability of existence of oneself (not the species but the individual) here you go:
https://www.theepochtimes.com/n3/787114-scientists-calculate-the-probability-of-your-existence/
Although I really want to check the math on this and haven't watched the Ted talk yet just read the article.

Wine&Cupcakes

URMySunshine77 said:

GhostMonkey said:

estoyborracha said:

I doubt it has much to do with evolution. Life expectancy really wasn't that much different 100 years ago than it is today, it just seems that way because infant mortality is down.

------------edit quote fail-------------

Also, women today are fertile earlier than in previous generations - having first menses around age 9 rather than 14 - likely because of hormones and changes in nutrition.

Not that any of that is useful or relevant to your original question in any way.

Even when adjusted for infant deaths, the age only goes up about 5 years. It's not like it jumps from 47 to 90. It goes from 47 to 52.

And getting your period sooner does not make you physically ready to bear children sooner. For those that start before age 12, at best 50% of their cycles are ovulatory.

Thanks for asking this, @BillyHorrible. It's something I've considered often.

@Ghostmonkey: Do you think that women who start menses later might be more fertile when advanced maternal age starts? I started my period at 15 and I'm 37. I've hoped that starting my period later might give me more eggs to work with at this point.

I believe this is true. Also, your rate of certain cancers will be lower due to less estrogen if I remember correctly from nursing school. But then again, don't quote me on that...at the time, nursing school also taught that marijuana was the only form of drug not shown to negatively impact a fetus and that's bunk now.

I'm reading TCOYF now - I believe they say -2 is best and that -3 through O are your overall best chances with -5, -4 and +1 being very slim likelihood.

The Great Sperm Race is awesome. I saw it a couple of weeks ago. Any documentary that uses people to act as sperm is an A+ in my book.

URMySunshine77

Wine&Cupcakes said:

@Ghostmonkey: Do you think that women who start menses later might be more fertile when advanced maternal age starts? I started my period at 15 and I'm 37. I've hoped that starting my period later might give me more eggs to work with at this point.

I believe this is true. Also, your rate of certain cancers will be lower due to less estrogen if I remember correctly from nursing school. But then again, don't quote me on that...at the time, nursing school also taught that marijuana was the only form of drug not shown to negatively impact a fetus and that's bunk now. I'm reading TCOYF now - I believe they say -2 is best and that -3 through O are your overall best chances with -5, -4 and +1 being very slim likelihood. The Great Sperm Race is awesome. I saw it a couple of weeks ago. Any documentary that uses people to act as sperm is an A+ in my book.

Thanks @WineandCupcakes. You are my new Bump crush.

Also, I just watched The Great Sperm Race tonight for the first time. I found it chilling but uplifting at the same time.

Pintobean39

Now I'm curious if the 20% chance also takes into account the miscarriages. I had heard once that 70% of all pregnancies end in miscarriages but most of the time no one even knows they are pregnant.

My RE was discussing the % of genetically correct eggs that he expected to get out of a cycle of IVF. He told me because of my age he expected possibly 15-20% but told me not to freak out to much about it because younger patients may only have 25-30% that are genetically normal. Now I've been on lots of drugs for an extended period of time so I could have my % a little or a lot off.