# What percentage of fertilized eggs actually result in a birth **URL:** \ **Category:** Factual Questions\ **Created:** [November 6, 2004, 2:07am UTC](https://boards.straightdope.com/t/what-percentage-of-fertilized-eggs-actually-result-in-a-birth/273301 "2004-11-06T02:07:41Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [November 6, 2004, 2:07am UTC](https://boards.straightdope.com/t/what-percentage-of-fertilized-eggs-actually-result-in-a-birth/273301/1 "2004-11-06T02:07:41Z")
I remember reading in an A&P book that only about 30-50% of all fertilized eggs actually made it through the third trimester and became a baby. What is the exact percentage of number of fertilized eggs that go onto become healthy fetuses and are born? This is based on the instant fertilization occurs, not waiting until the first trimester, or waiting until the zygote implants in the uterus, etc. This is when the egg and sperm merge in the fallopian tube, how many of them go onto become healthy babies. This isn’t an abortion debate BTW, i’m just looking for statistics. ---
**Author:** ![kniz](https://avatars.discourse-cdn.com/v4/letter/k/c37758/32.png) [@kniz](https://boards.straightdope.com/u/kniz)\ **Post date:** [November 6, 2004, 3:44am UTC](https://boards.straightdope.com/t/what-percentage-of-fertilized-eggs-actually-result-in-a-birth/273301/2 "2004-11-06T03:44:05Z")
Is this a trick question or a test of our intelligence? The information you cite says **all fertilized eggs** and not anything about attaching to the uterus. Even if you have made a meaningful distinction, the 20% range between 30% and 50% should easily cover whatever that distinction may be. :rolleyes: ---
**Author:** ![WhyNot](https://avatars.discourse-cdn.com/v4/letter/w/c77e96/32.png) [@WhyNot](https://boards.straightdope.com/u/WhyNot)\ **Post date:** [November 6, 2004, 5:16am UTC](https://boards.straightdope.com/t/what-percentage-of-fertilized-eggs-actually-result-in-a-birth/273301/3 "2004-11-06T05:16:57Z")
Didn’t you answer your own question? 30-50% make it, so 50-70% don’t. These sound like theoretical numbers to me. I’ve never seen a research number for this, primarily because there are many conceptions and very early miscarriages which go unnoted by even the mother and therefore unreported. A fertilized egg is so tiny that if it fails to implant and is washed out with the menstrual flow, there’s no way it will be seen. A miscarriage at 4 or 5 weeks may be interpreted as a “heavy late period.” A good friend of mine just lost one after 7 weeks, and there was a piece of tissue in her flow about the size of a nickel. She said she wouldn’t have noticed it if she hadn’t been looking for it. In fact, even though she’d had positive pregnancy tests and an ultrasound, her doctor told her it wouldn’t go on her medical records as an abortion (medispeak for “miscarriage”), it would be listed as delayed menses, because she only missed one menstrual cycle. [PubMed](http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12095488&dopt=Abstract) has this about one IVF study, but I wouldn’t feel comfortable extrapolating that data to healthy couples conceiving the old fashioned way: > [@](#): > > RESULT(S): **The cumulative conception rate and cumulative live birth rate after four attempts were 75% and 66%, respectively.** The cumulative conception rate differed significantly between women 35 years of age or younger and those older than 35 years who had five or more oocytes retrieved (83% vs. 63%). When fewer than five oocytes were retrieved in women 35 years of age or younger, the cumulative conception rate decreased to 33%. Overall, 36% of patients continued treatment after the first attempt; these patients were more likely to have more than five oocytes retrieved and more than two embryos available for transfer. ---
**Author:** ![Wesley\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/wesley_clark/32/20581_2.png) [@Wesley\_Clark](https://boards.straightdope.com/u/Wesley_Clark)\ **Post date:** [November 6, 2004, 1:34pm UTC](https://boards.straightdope.com/t/what-percentage-of-fertilized-eggs-actually-result-in-a-birth/273301/4 "2004-11-06T13:34:48Z")
> [@kniz](#): > > Is this a trick question or a test of our intelligence? The information you cite says **all fertilized eggs** and not anything about attaching to the uterus. Even if you have made a meaningful distinction, the 20% range between 30% and 50% should easily cover whatever that distinction may be. :rolleyes: Very helpful.