Mathematical models used to determine sperm donor limits for infertility treatment

21 11 2008


To the Editor:

In the August 2008 issue of Fertility and Sterility, Sawyer and McDonald provide a useful and insightful review of mathematical models used to determine sperm donor birth limits (1).  The review is timely, given recent policy deliberations around gamete-donation. 

Worldwide, advocacy groups, governments, and gamete-donation programs strive to identify and implement policies that promote the best interests of the recipients, donors, and donor-conceived people.  As discussed, donor limits are typically determined by attempts to minimize the risk that donor-linked individuals will have children together.  We agree that mathematical modeling is useful to determine these limits in cases when donors are anonymous and parents do not disclose their children’s donor origins.  However, when families are more open and/or when single women and lesbian couples represent the majority of donor insemination (DI) recipients (e.g., in the US), additional consideration needs be given to the phenomenon of contact among individuals and families who share the same donor (2). Meeting a few or even 10 donor-linked families can be joyous and incredibly positive; the impact of meeting 25-50 families may be more challenging and even negative. We suggest that birth limits may be better determined by psychological factors primarily, and then secondarily informed by modeling based on consanguinity risk.

Following this, we suggest that with open-identity donation (e.g., in Victoria, Australia), psychological factors should be the primary determinant.  In this case, the limit should be the number of individuals with whom a donor can have meaningful interactions.  Indeed, the goal of open-identity donation is to meet the needs of donor-conceived adults by providing access to genetic and medical information and addressing questions of origins and ancestry.  No doubt this will result in lower birth limits per donor than one determined by consanguinity risk.  

Finally, as Sawyer and McDonald’s review will likely provide material for limit-setting deliberations, note that some of the limits have changed, likely due to the rapidly changing environment of assisted reproduction. For example, in the United Kingdom, donor limits are specified by families (10 per donor), not by births (3). In the United States, the limits actually differ from the United Kingdom and are recommended, not regulated, to be 25 births per donor per population of 800,000 (4). Thus, many programs in the United States will have higher numbers of individuals born per donor than the 10 nationwide listed in this article. Knowing that these numbers vary widely and how they may impact the people and families created through gamete donation should provide us with impetus to more closely consider how DI is practiced. 

Joanna E. Scheib, Ph.D.
Department of Psychology 
University of California  
Davis CA 
The Sperm Bank of California 
Berkeley, CA 

Alice Ruby, M.P.H., M.P.P.M.
The Sperm Bank of California
Berkeley, CA

1. Sawyer N, McDonald J. A review of mathematical models used to determine sperm donor limits for infertility treatment. Fertil Steril 2008;90:265-271.

2. Scheib JE, Ruby A. Contact among families who share the same sperm donor. Fertil Steril 2008;90:33-43.

3. Human Fertilisation and Embryology Authority (HFEA). Code of Practice. 7th ed. London 2007. Available at Accessed August 2008.  

4. Practice Committee of the American Society for Reproductive Medicine, Practice Committee of the Society for Assisted Reproductive Technology. Guidelines for gamete and embryo donation. Fertil Ster 2006;86:s38-s50.
Published online in Fertility and Sterility doi:10.1016/j.fertnstert.2008.12.071

The Authors Respond:

We very much appreciate Scheib and Ruby’s comments and the insight they too have brought to this very topical issue. They have made some very valid and interesting points in regards to criteria for determining
birth limits for donor insemination (DI).

As they mentioned, here in Australia there is a view that, in an environment open to disclosure and where children are informed of their donor roots, psychological factors may well be the primary determinant of donor limits. However, the risk of donor-linked individuals having children together is still present,
as is currently the case in the US where anonymity is still the norm (1, 2). So, although the authors agree that with open-identity donation the psychological factors should be the primary determinant they believe
there is still a need for modelling if open identity is not being practiced and jurisdictions require criteria on which to base limits. We agree that there is a need to more closely consider how DI is practiced and suggest that the establishment of a nationally mandated gamete registry would assist in the establishment of limits based on both psychological factors and risk of inadvertant incest.

Neroli Sawyer, B.Sc.
School of Information Technology and Mathematical Sciences
University of Ballarat
Mount Helen, Ballarat, Victoria, Australia

1. Cahn N. Necessary Subjects: The Need for a Mandatory National Donor Gamete Registry. DePaul Journal of Health Care Law, 2008.

2. Sylvester T. The Case against Sperm Donor Anonymity: Yale Law School; 2007.
Published online in Fertility and Sterility doi:10.1016/j.fertnstert.2008.12.072 
















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