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How Many Embryos Are Left Over?

Posted by Pete Shanks on October 8th, 2008

Embryo freezing

The Los Angeles Times series on frozen embryos (discussed yesterday) says that "almost 500,000" embryos are in freezers. That's consistent with a 2003 RAND study, which estimated "nearly 400,000." But how many become available each year?

No one seems to know. The Centers for Disease Control (CDC) do not publish data on embryo creation or disposal. Still, we can use the data available to suggest very roughly how many potentially viable unused embryos are either stored or destroyed each year in the course of fertility treatment.


  1. Only eggs from women under 35 are considered (for quality reasons).
  2. Fifteen eggs are generated in a successful cycle (the middle of this range).
  3. Half the recovered eggs are fertilized (a guess).


  1. 41,302 women under 35 underwent a cycle of hormone treatment in the U.S in 2005, the most recent year for which data is available.
  2. 92% had eggs successfully retrieved = 37,998 women.
  3. An average of 2.4 embryos were transferred per woman under 35.


284,985 embryos were created, and 91,195 transferred. Thus a gross total of 193,790 embryos were left over. But far fewer are available.

A full 63% of the women who started cycles in 2005 did not achieve a successful live birth, so the RAND estimate that 88.2% were reserved for "future family building" seems plausible. Indeed, if we accept their conclusion that only 2.8% of frozen embryos are actually available for research, the annual number would be only 5,426.

This is absolutely a back-of-the-envelope calculation. A conscious effort to encourage donation might raise it, as would higher egg retrieval and fertilization rates. But it's hard to see more than 20,000 a year being available nationally.

Of course, when Harvard cannot find ten in two years, even 5,000 sounds like a large number.

Previously on Biopolitical Times:

Leftover embryo quandaries

Posted by Marcy Darnovsky on October 7th, 2008

A set of three articles in Monday’s Los Angeles Times discusses the often difficult dilemma faced by people who have frozen embryos that they don’t want to use for their own reproductive purposes. Their options: discard them; give them to someone else who wants to try an IVF pregnancy; or donate them for research, usually to derive stem cells.

Though these decisions are of course deeply personal, they are also – especially in the U.S. – intensely political. Typically, the hot button that's implicated is abortion rights. But there are other issues involved as well, and these non-abortion matters often go unnoticed.

The LA Times report on donating embryos for research is a case in point. It does a good job exploring the obstacles faced by people who want to give their embryos to researchers – “piles of paperwork,” getting the consent of third parties whose gametes created the embryo, and the like. Another difficulty, the article says, is that many IVF clinics don’t have close connections to researchers; the implicit suggestion is that these sorts of ties should be encouraged.

Here’s where some additional consideration is warranted, in order to minimize conflicts of interest that could adversely affect people using IVF services. Doctors' first responsibility should be to their patients, not to their research – and unfortunately, violations of this principle are all too common.

In the California stem cell arena, we’ve already seen a case that raises eyebrows. Recently, two medical professionals at an IVF clinic were co-authors of a scientific paper [PDF] about the first successfully cloned human embryos. The doctors at The Reproductive Sciences Center actually report to the head of the biotech company conducting the research, Stemagen Corporation.

What this means is that these doctors, who may well have been responsible for determining the dosages of hormones received by the women who provided the eggs for the cloning technique, had a significant interest in the positive outcome of the research.

As with other kinds of conflicts of interest, the problem goes beyond the integrity of anyone’s conduct or the virtuosity of intentions. The fact of this matter was that the more eggs retrieved, the better the chances of the research's success and the researchers' plum byline.

This particular sort of conflict of interest is more worrisome when the biological material in question is eggs, rather than embryos. Embryos aren’t as scarce as eggs; and whereas eggs must be used very soon after they’re extracted, embryos are almost never available for many months (until the parents have completed their family or given up).

Nonetheless, and notwithstanding the need to ease the way for people who wish to donate their unused embryos for research, the potential for conflicts of interest should not be overlooked.

Third Time a Charm for Stem Cell Bill? Probably Not

Posted by Jesse Reynolds on October 4th, 2008

Photo by Flickr user ismasans under a Creative Commons license

A bill to overturn President Bush's restrictions on the federal funding of human embryonic stem cell research has been introduced - yet again. Although Bush vetoed similar bills twice already, and there's still not enough Congressional support to override the veto, Diana DeGette (D-CO) and Mike Castle (R-DE) have unveiled the Stem Cell Research Enhancement Act of 2008.

Its only difference from past attempts is that the "ethical oversight" that the bill's backers have been touting for some time has been added. This is a big step in right direction, since voluntary guidelines from the National Academies are currently the closest thing to national oversight.

But unfortunately, the new DeGette-Castle bill would require the National Institutes of Health to draw up guidelines that would apply to only federally-funded stem cell work. This wouldn't just leave a patchwork of policies depending on whether work is funded by the federal government, a state, or a private source. Privately-funded stem cell researchers would remain essentially free of oversight. Considering that the most controversial avenue - cloning-based stem cell research - is led by two private companies (1, 2), and that there's still no federal ban on reproductive cloning, this is a significant gap.

Although the addition of NIH guidelines may pick up a couple votes, it won't change enough minds for a veto-proof margin. Why would Reps. DeGette and Castle introduce a bill that has no real chance of becoming law? Let's remember that there are also Congressional elections coming up on November 4. Although embryonic stem cell research has not been a high-profile national issue this year, it can still be an effective wedge issue against some vulnerable Republican Representatives and Senators. They'll be put on the spot, and asked to take a position on an issue that could cost them some support.

Furthermore, Congress members may be seeking stem cell credit: The bill's sponsors and Congressional leaders might prefer if Bush's restrictions were lifted through legislation instead of a Presidential executive order. The bill can be refined now, and then one with all the necessary edits could be sent to a new president immediately after his inauguration.

Any other theories? Feel free to comment.

Previously on Biopolitical Times:

How the (Not so) Mighty Have Fallen

Posted by Osagie Obasogie on October 2nd, 2008

Just three years ago, NitroMed (makers of BiDil, the first FDA-approved race specific medicine) was heralded as a promising pharmaceutical company with a business model for BiDil that led some analysts to predict sales of between $500 million and $1 billion by 2010.  

Yet, BiDil’s fortunes have swung drastically in the other direction. Amongst sluggish sales and massive layoffs, Nitromed was recently notified by NASDAQ that its stock risks delisting since its price has been below the $1 minimum for over 30 straight days.

What does NitroMed’s slow but steady demise mean for future endeavors into race based medicine? It’s hard to pinpoint exactly why BiDil failed. Some say it was overpriced compared to the availability of its constitutive generic components at a fraction of BiDil’s cost. Others suggest that the fraught history between Blacks and the medical community may have led many African Americans to think twice about taking any medication claimed to be designed just for them.

Regardless of the reason, it seems that even BiDil’s strongest supporters are starting to rethink their approach. One of them, Dr. Keith Ferdinand, told the Newark Star Ledger that “he now wonders whether the smarter strategy would have been to market BiDil as a general heart failure drug and let the data about its particular effectiveness in blacks ‘stand on its own.’”

Not a bad idea.

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