What % of fertilized human eggs die?

December 16, 2011 3:34 PM

What % of fertilized human eggs never attach to the uterine wall?

I'd be grateful for informed estimates as to the # or % of fertilized human eggs that never attach to a uterus wall and then are passed out during the next menstruation.

I know that if a fertilized egg attaches it usually does so w/in the first 6-12 days. But I haven't found a reasonably authoritative source that gives a rough estimate of how many/what % of fertilized eggs don't make it past this first phase.

The data are part of a discussion over the view that "life begins at conception." For example, if most fertilized eggs never attach to the uterine wall, the view is committed to the majority of humans having died at this early stage.

posted by airing nerdy laundry to Science & Nature (10 answers total)

"It's hard to know for sure, but researchers have estimated that 40 to 65 percent of conceptions end in miscarriages. And more than half of those occur so early that pregnancy is not even suspected yet (miscarriages that happen in the first few weeks of pregnancy are called chemical pregnancies or blighted ovums — meaning that the fertilized egg failed to implant or develop for unknown reasons)." (source)
posted by litnerd at 3:42 PM on December 16, 2011 [1 favorite]

http://www.eubios.info/TM.htm suggests a 30-40% normal implantation rate.
posted by michaelh at 3:44 PM on December 16, 2011

When I was struggling to get (and stay) pregnant, I was told that in an optimally fertile woman, only about 30%-40% of embryos implant successfully, and that in cases of even subclinically compromised fertility, it could be as low as 10-20%. The intricate dance that has to happen for implantation to be successful is incredible, it's amazing it ever works right.
posted by KathrynT at 4:06 PM on December 16, 2011

When my friend was doing IVF (not for any fertility problems that would affect implantation), her doctor told her the expected rate of attachment (i.e. success when she had a transfer of a viable embryo), was between 25 and 60%, depending on all sorts of factors that I don't recall right now.
posted by lollusc at 4:08 PM on December 16, 2011

Response by poster: Thanks guys! I don't have any reason to doubt these sources, but am surprised at the lack of links to any primary sources on the net generally.

I'm a little reticent to go spouting off these stats w/out some idea of where these sites get their info. from. ... I guess I'd like to appear a little more authoritative if I mention this for instance in a college class.
posted by airing nerdy laundry at 6:16 PM on December 16, 2011

You can always see about interviewing a local obgyn for a quotable source.
posted by litnerd at 6:21 PM on December 16, 2011

PDF: “SUMMARY: Implantation is arguably the most critical stage in the establishment of pregnancy. In humans, it has been estimated that between 30% and 70% of conceptuses are lost before or at the time of implantation”. The cited statistic comes from this article. If you have journal access you should be able to chase those references as far as you like. More PubMed.
posted by hattifattener at 7:19 PM on December 16, 2011

I did some shallow searching (because apparently anything is more fun than working on my own research) and found a few articles that I could comprehend:

Wilcox AJ, Weinberg CR, O'Connor JF, et al. Incidence of early loss of pregnancy. N Engl J Med 1988;319:189-94.

Zinaman MJ, Clegg ED, Brown CC, O'Connor J, Selevan SG. Estimates of human fertility and pregnancy loss. Fertility and Sterility 1996;65:503-9.

Hertig AT, Rock J, Adams EC, Menkin MC. Thirty-four fertilized human ova, good, bad and indifferent, recovered from 210 women of known fertility: a study of biologic wastage in early human pregnancy. Pediatrics 1959;23:202-11.

Wilcox AJ, Day Baird D, Weinberg CR. Time of Implantation of the Conceptus and Loss of Pregnancy. N Engl J Med 1999;340:1796-1799

Macklon NS, Geraedts JPM, Fauser BCJM. Failure of implantation and its relevance to subfertility. Human Reproduction Update 2002;8:333-343.

If I'm reading right, these studies all seem to indicate that 20-30% of embryos fail to implant. Like hattifattener suggested, you can delve into the references to explore more thoroughly.
posted by bethnull at 7:55 PM on December 16, 2011

I've read some of this research as an interested layperson, and one thing that stood out to me isnhow many of these studies deal with fertility treatment. This makes sense, as its really impossible to measure how many embryos implant in normal populations since you don't know how many are produced and how many make it to the uterus. What this means, from my reading, is that all the statistics involve known fertility issues. This does not make them worthless, but does argue for caution.
posted by OmieWise at 2:56 AM on December 17, 2011 [1 favorite]

It also doesn't obviate any points re this data and "life begins at conception" arguments.
posted by OmieWise at 2:43 PM on December 17, 2011