Where does the 20-25% chance statistic come from?

I keep seeing this here in the ttc section and also elsewhere on the internet. Supposedly, even if you have sex at the right time, during ovulation, your chances of pregnancy in any given cycle are only 20% (or 25%, 30%, I've seen a few different numbers). Where on earth does that come from? I did a google search and found similar statement on tons of different ttc sites, but no explanation of why or what research that is founded on. I found one Y!A question on the topic, and every answer had a completely different explanation. I would like to know where this comes from, and on what research is it based? Please don't just give me your theory of why that is - I would like to know who told you that or better yet provide links to the research that supports it. Otherwise I'm inclined to think it's just something some doctor made up to make people who are ttc be patient and not get frustrated right away.

2011-07-06T18:40:35Z

For what it's worth, it definitely doesn't apply to me - I have had no trouble getting pregnant. I was 22, 24, and 27 when I conceived each of my 3 babies.

Anonymous2011-07-12T13:43:51Z

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When I was ttc I heard this statistic thrown around on here a lot as well.

I had no problem getting pregnant, and did the first month that I tried, as did a lot of my friends. I'm not really sure where this statistic comes from either, as I just tried to do some research on it and couldn't find any actual evidence. But I can tell you that my OB told me at my six week check up that if I was one of the few people that happened to have an IUD fail on them, and ovulated, I would have a 25 percent chance of getting pregnant like someone who wasn't on birth control. So I guess there must be some sort of evidence linked to the statistic for my OB to say it? Or maybe it really is just something that a doctor made up to help ttc patients be more patient?

I'll try to research it more, and if I find anything out, I'll let you know!

Suzy Q2011-07-07T04:50:02Z

Simply statistics from real life. Most women get pregnant at some point in their lives, so collecting data is very easy. There's tons of research on how different things (weight, smoking, drinking, diet, lying down after sex, age etc. etc.) affect the chances of conception, and in all that research the control group also yields valuable results. Also doctors can simply use the information pregnant women give about when they stopped using contraceptives. Meta-research on all those data can tell us how high the average chance of getting pregnant is per cycle.

?2011-07-14T13:54:34Z

It is an average number from studies. That is the median number given. Obviously there are women like you who get pregnant easily. Than they are some it takes a year or 6 months. It is just an average. The fact of the matter is the majority of woman are not like you. It is the same as estimating ovulation. They say women ovulate on cycle day 14. In fact over 1/2 women don't because cycle lenghta fluctuate. Don't take the numbers so literally.

?2016-10-22T08:09:33Z

If the percentages have been so against us, we does not be overpopulating the planet now. learn your self to maximum different mammals. they have 2 possibilities a three hundred and sixty 5 days, some purely one risk. the two they get pregnant throughout the time of their very short estrus or they have lost out for yet another 3 hundred and sixty 5 days. You get 12 possibilities. The estimate is consistent with honestly pregnancies, not the style of sperm and confident does not contain the style of miscarriages that girls did not even know that they had. maximum of those sperm die in the past they even make it to the fallopian tube. not all eggs are doable. maximum women do not ovulate each month even with getting a era each month. particularly, it rather is a crap shoot it is weighted certainly for being pregnant.

whatapwrtrip2011-07-06T18:34:17Z

maybe it applies to women who are older, like 20-40, who have less chance of getting prego.