I don’t know about the stress, but I know a female orgasm is important, since those undulations pull semen toward the phallopian tubes. An unexcited woman isn’t much good, I wouldn’t think.
Well, if you’re going to factor in that, you have to factor in problematic elements such as miscarriages, etc. as well. Just trying to keep it real.
If we use Whynot’s 85% annually statistic and assume 1 session a week for the average couple I calculate around 3.5% chance of pregnancy per each encounter. Is that 85% figure assuming that the couples are trying to get pregnant, or just not using birth control? I might have to revise the 3.5% number a bit depending on that. Since I’m really uncertain, and zut cites a 5% rate, lets be really generous and say an especially virile man could have a 10% impregnation rate per encounter. I’d guess around 150 a year, higher if he got “lucky.”
I don’t know if you’ll accept a class syllabus as authoritative but I just finished a med school class on the reproductive system. We were taught that if a woman has unprotected sex for a year with “normal” frequency she has a 85% chance of getting pregnant. Normal being twice a week.
I don’t think you can just do it that way: you are assuming that each act is an independent event, and all women have the same likelihood. Some women (or couples) are infertile, so they have 0% chance each time. To take an extreme possibility, if 15% of women were infertile, and the other 85% had a 100% chance on every act of intercourse, you would get the same result – 85% pregnant after a year – but you would also have 85% pregnant after 1 week.
I’m assuming that fertility rates average out. I don’t see how there could possibly be a better way to do it unless you have have precise data on a few hundred million couples.
Well, first you have to factor in that some women of normal child-bearing age are infertile. I don’t know how many, but the number is significant. If 10% of women are infertile, then of the other 90%, 85/90 are going to be pregnant after a year. For them, assuming each week is independent, and they all have the same likelihood, they have a 5.4% chance of being pregnant after a week. So the average for the fertile + infertile is about a 4.85% chance per week. So that’s changed the figure already. But the fertile women don’t all have the same likelihood each week – some might be 10%, some might be 2% – and that will change the average per week again.
Well, the whole uncertainty is why I bumped up my figure a lot. Is it knowable which women are very fertile? If you found 2,000 of the most fertile women in the world and had a guy have sex with them all, you’d have a high number for sure.
Given that women have a monthly cycle of variation in fertility, I would think it pretty easy (given an unlimited supply of willing women of at least average fertility) to get a 15% to 20% change of pregnancy with each act of intercourse. When I was younger, that would have meant I could have sired a child most days!
Note too that the impressive score of about 16 million descendants, if indeed attributable to Genghis Khan, wasn’t due solely to the Big G himself. His sons and grandsons also had exceptional access to sexual partners and consequently disproportionately large numbers of offspring.
Having as many offspring as possible in just one generation, and then having all those offspring revert to normal fertility patterns, doesn’t boost your descendant population as much as having the hyperfertility spread over several successive generations, AFAICT.
That’s factored into the 3-5 days I quoted earlier. Sperm can, with great quality fertile cervical fluid, live up to 5 days, in theory (I conceived after 6 days, but I’m pretty much a baby making mutant.) So if we have sex on the 1st and I ovulate on the 4th, we’re still likely to make a baby. It’s pretty unlikely to achieve pregnancy with sex at or after ovulation, though - the sperm needs to already be in the fallopian tubes when the egg is released. If you wait until ovulation, the egg will have made its way into the uterus before fertilization, and at that point it’s usually not going to attach, or it will attach too low and the placenta will abrupt, resulting in a miscarriage.
Most women have about 3 days. Some less, some more, but 3 is solidly in the middle of the bell curve.
I got it from any number of medical sources, I can’t claim a single source. If you google contraceptive failure rates, you’ll get a mess of hits, and almost all of them include “No method” on their charts. It is the accepted baseline number for all couples - fertile, infertile, trying to conceive, not caring one way or the other.
You are either a very lucky man, or you’re attracted to subfertile women. 
AH! Sweet, twice a week. That was an important number I did not know how to find. Thanks!
Well, kinda sorta. That is, women who get pregnant a lot tend to be more fertile. (duh) So we might want to limit our brood to only women who are already mothers, and young mothers at that - since fertility starts to drop at age 30, and drops dramatically at age 35. But when I was talking about using only fertile women, I was talking about using only women during their fertile days - and that’s pretty easy to tell on most women if you take their morning temperature before rising and track their cervical mucus.
You have to figure in the miscarriage rate, which I think is minimally about 25% or so of all pregnancies.
Thailand’s (or Siam’s) King Chulalongkorn, aka Rama V and who reigned from 1868-1910, had at least 77 children.
Suppose every woman he had sex with was within about three days of ovulation, though. Making a near-perfect scenario. Given good conditions, what’s the pregnacy rate there? The likelihood still wouldn’t be 100%, but what sort of percentage might we be looking at?
Wouldn’t the guy have to take some time off to replace his sperm. The more sex a guy has, the fewer the sperm in subsequent acts. Eventually he would be temporarily infertile.