With an increasing number of single women pursuing pregnancy, the Center for Human Reproduction is constantly being asked whether to try embryo donation or individual sperm and egg donations, to create embryos. Not less frequently, a similar question comes up for couples, though in such cases, the "partner factor" also comes into play: is giving the male partner an opportunity to be the genetic father an advantage, or disadvantage, for a given couple?

While this question is not what we want to address here, the basic choice between embryo donation and separate egg and semen donations (or partner sperm) requires some technical clarifications. We are concentrating on technical issues here, because we cannot, and do not wish to, comment on personal preferences, religious beliefs and other motivations that may lead to one or the other choice. Our purpose here is simply to compare what objectively lends itself to comparisons: the outcomes.

So, let's start with embryos: They are the embryos produced in the course of infertility treatments and, therefore, derive from couples who themselves suffer from infertility. These embryos generally come from eggs of women older than egg donors, who are usually in their 20s. Moreover, one can further assume that ovarian problems will be much more frequent amongst infertility patients than egg donors. Thus, there can be little doubt that egg quality (and embryo quality) with egg donation will be substantially higher.

Donor embryos are usually those embryos an infertile couple has left over after conceiving on their own. In other words, it is very likely that a couple's best-looking (likely also their best-quality) embryos were used first. Donated embryos, therefore, represent a couple's "second choice" embryos. Statistically, this, likely, means that donated embryos are embryos with lower pregnancy chances than the couple's "first choice" embryos that led to their own pregnancy.

Finally, donated embryos are always frozen (cryopreserved), while donor eggs, and the embryos that come from donor eggs, at least in the initial embryo transfer, are always fresh. Fresh embryos, of course, always have a slightly better pregnancy chance than cryopreserved/thawed embryos.

Adding up all of the above technical advantages of donor eggs over donor embryos, it is not surprising that egg donation will give patients much higher pregnancy chances per cycle than embryo donation.

Two additional advantages of egg donation need to be considered: At least at CHR, egg donation gives patients the option of selecting donor characteristics quite in detail. Embryo donation, in contrast, rarely offers the option of selection beyond basic race/ethnicity. Since CHR, likely, offers the largest and most diverse egg donor pool anywhere in the world, in most cases, our patients have excellent options to "match" their donor in looks and characteristics with the recipient.

And, while one embryo donation cycle, of course, is significantly less costly than one egg donation cycle, the question is not the costs per cycle but the total costs incurred before the patients have a baby at home. Looking at costs from such a vantage point, egg donation, once again, probably represents the better option.

In summary, while there may be social, psychological, religious and other personal reasons for choosing embryo donation over egg donation, an objective analysis, solely concentrating on technical outcome and cost, finds little in favor of embryo donation and overwhelmingly favors egg donation.

The Center For Human Reproduction in New York, NY specializes in infertility treatment, egg donation and research related to fertility. Their website is www.centerforhumanreprod.com