Question: I am an OB/GYN in the bay area and I have a patient that is interested in having a baby girl. She asked about “sperm spinning” as a method of gender selection and whether it would be useful in her situation.

Answer: Our office receives a lot of questions from patients and members of the public about sex selection. Our location in the very liberal San Francisco may be cause for the increasing demand we see in having a baby of a predetermined gender. People are also well informed about what can be achieved with modern technology, and since sex selection is a reality, there’s definite demand for it.

The procedure that you ask about, “sperm spinning” is better known in the medical and scientific communities as the “Ericsson Method”. The technology was developed by the German scientist Dr. Ronald Ericsson and has been licensed in the US and internationally since the early 1970′s. It takes advantage of the fact that sperm bearing a Y chromosome (that would make a boy) are very slightly lighter than X-chromosome bearing sperm (that would make a girl). The distribution of X and Y bearing sperm in a normal sperm sample is equal, but Ericsson’s method uses gentle centrifugation of sperm through a slightly viscous fluid to segregate the heavier (girl) sperm from the lighter (boy) sperm. Since the difference in the weight of the 2 types is so slight (about a 3% difference in amount of DNA), a perfect separation cannot be achieved. Ericsson’s website (www.childselect.com) claims a 78-85% success rate in couples seeking a boy and a 73-75% success rate for girls. At PFC, we do not endorse or recommend this method of sex selection, nor can we verify the above success rates. As far as we know, couples availing of sperm spinning are not given details of how well purified their samples are prior to using them for insemination.

A more reliable method for separating sperm in our opinion is the “Microsort” technique offered at the Genetics and IVF Institute (www.givf.com) in Fairfax, Virginia. The technique was developed originally by Dr. Lawrence Johnson at the US Department of Agriculture, and was later refined for use in humans in collaboration with GIVF. Microsort also takes advantage of the small difference in DNA content between “boy” and “girl” sperm. The sperm are dyed with a stain that binds to DNA and then an instrument called a flow cytometer can effectively separate populations of sperm based on how much dye they have incorporated. The Microsort scientists test a small aliquot of every separated sample to determine the exact enrichment that they have achieved. According to the latest figures posted on their website (microsort.net) the average enrichment for X-bearing sperm is 88% with 91% (525/574) of babies born being female. The technique is less effective for Y-bearing sperm with an average sample purity of 73% and 76% (127/152) of babies born being male. Bear in mind that the figures for babies born might be distorted since some patients may have terminated pregnancies that were not the gender that they were seeking. You may also have noticed from the GIVF data that there’s more demand for girls than boys. This is likely due at least in part to the fact that X separations work much better and therefore may be used more, but Dr. Ericsson’s website also claims a much stronger female demand even though his technology supposedly works better for boys. We do support the use of Microsort sperm here at PFC but there are limitations on the use of this technology. First, the sperm can only be separated in 2 laboratories in the US, (Fairfax and Huntington Beach in southern California), and the Microsort researchers prefer that you attend in person to give a fresh sperm sample. Second, the technology is currently only offered under an FDA approved clinical trial, and you have to be doing family balancing or trying to avoid a sex-linked disease in your family to be enrolled. For most people, unless you already have a child of a different gender from the one you are seeking, you won’t be able to participate in this FDA study.

Last, but not least is preimplantation genetic screening (PGS) that can be used to tell the sex of embryos created during in vitro fertilization (IVF). We feel that this technology is the most accurate of the sex determining strategies since there’s less than a 3% chance of a misdiagnosis. Embryos generated in an IVF cycle are subject to a biopsy procedure on the third day of growth that allows a single cell from the embryo to be analyzed to see if it has 2 X chromosomes (female) or X and a Y chromosome (male). IVF with PGS is the most accurate method for sex selection, but also the most involved and the most expensive. The Ericsson method is the easiest and the cheapest, but carries a greater risk of being inaccurate.

Joe Conaghan, PhD

Tags: Bay Area, Gender Selection, IVF - In Vitro Fertilization, PGS - Preimplantation Genetic Screening, Treatment Options

This entry was posted on Wednesday, June 20th, 2007 at 12:54 pm and is filed under Ask The Experts. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.