This summer, we are introducing a new procedure in our laboratory that will allow us to do genetic testing on embryos that have reached the blastocyst stage of development. Traditionally, embryos are biopsied when they are just 3 days old at which time they should have reached the 8-cell stage (see figure 1). The biopsied cell is sent to the genetics laboratory for testing while the remainder of the embryo continues to grow in our laboratory. The genetic testing results are received 48 hours later, when we hope that the embryo will have reached the blastocyst stage (see figure 2). Blastocysts that have passed genetic screening can be transferred or frozen for later use.

Performing the biopsy when the embryo has become a blastocyst is more technically challenging, and it allows less time for the genetics lab to do their testing. However, in a blastocyst, we are specifically able to biopsy from the part of the embryo that will become the placenta, and we can get more than 1 cell, which allows for greater accuracy in the genetic testing. Depending on how quickly the test is run, the embryo may have to be frozen while we wait for the results.

While freezing is inconvenient, it does allow time for more complex genetic testing, and for multiple tests if necessary. And, with the success of vitrification for preserving embryos (see Fertility Flash Vol. 7, Issue 3), we are confident that the frozen embryos will survive and implant at high rates when thawed.

In the next few years, we expect that the traditional methods for biopsy and genetic testing will disappear and that blastocyst biopsy will be the standard procedure. As genetic testing evolves, it will not be possible to rely on just a single cell from an embryo to get dependable results. We already know that there is genetic variability among cells in an individual embryo, a phenomenon known as mosaicism, and our new procedure will overcome this problem.

In the coming months, we will announce an exciting new partnership with a Bay Area genetic testing lab, and we will keep readers informed on our progress with genetic testing in embryos. This is an exciting field that continues to evolve.

Joe Conaghan, Ph.D., HCLD is PFC’s laboratory director. Dr. Conaghan is internationally recognized for his work on improving embryo culture conditions. His interests include developing programs for the treatment of severe male factor infertility; diagnosis of genetic disease in embryos; and improved embryo culture.

Pacific Fertility Center is pleased to share our delivered pregnancy rates for 2007 and our preliminary clinical pregnancy rates for 2008. These outstanding pregnancy rates are made possible thanks to our team of board certified Reproductive Endocrinology and Infertility specialists, as well as, our highly trained embryologists.

Clinical pregnancy reflects the finding of a pregnancy sac in the uterus following transfer. Delivered pregnancy rate will be lower after accounting for miscarriage and pregnancy loss, particularly in older age groups.

Pacific Fertility Center Preliminary Clinical Pregnancy Rates for 2008

Delivered Pregnancy Rates 2007 (as reported to SART and CDC)

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 (http://microsort.net/index.php) 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, Ph

For many people, the dream of having a family also includes the dream of having children of both sex. Since most families today are much smaller than in generations past, the odds of having two or three or even four children of the same sex is fairly high.

Throughout human history, there always has been interest in methods to sway the chances of conceiving a child of a particular sex. Today, in the 21 st century, it is quite clear that many of these sometimes bizarre and sometimes simple home remedies have no basis in fact.

There are ways to significantly shift the odds of having a child of one sex or another. Sex is conferred on an embryo by whether an X-bearing sperm (for a girl) or a Y-bearing sperm (for a boy) enters the egg. Unfortunately, despite highly publicized claims, there are no proven effective “at home” methods of sperm separation. Nor does timing of intercourse relative to ovulation affect the 50:50 sex ratio. By natural methods, the ratio remains a flip of the coin.

The only commercially available method for sperm separation that appears to be effective is the sperm sorting process available through Microsort.net. This method involves using a fluorescent DNA dye that attaches to either X or Y chromosomes. The sperm then passes through a cell sorter that separates the sperm based on the fluorescence. This method is still under FDA investigation for safety and efficacy but does appear to do a reasonable job in separating sperm, especially if the desired sex is female.

Mirosort reports a 90% success rate with separating X-bearing sperm and a 73% success rate in separating Y-bearing sperm. There have been only a few hundred babies born thus far, but there does not appear to be any increase in birth defects. Because this process is still considered “experimental,” couples wishing to participate, will have to travel to either Fairfax, Virginia (Microsort headquarters) or an affiliated clinic in Southern California for fresh sperm insemination.

Unfortunately, after Microsort processing, the number of sperm available for insemination is severely decreased. Freezing and thawing of sperm, which would allow the sample to be shipped to another location, reduces these numbers even further. Because sperm counts are so low after sorting, it is usually necessary to do in vitro fertilization with sperm injection (IVF-ICSI) to significantly improve the fertilization in the IVF laboratory. PFC is a participating site in the FDA investigation for Microsort. We have used sperm specimens that had been previously Micro-sorted for IVF-ICSI.

Researchers at UC Irvine recently published a study describing the use of lasers to “trap” the heavier and slower moving X-bearing sperm to separate it from the lighter Y-bearing sperm. In the future, this process may provide an alternative to Microsort. However, it is not yet commercially available.

Beyond the Microsort technique, the only way to improve the odds of selecting one sex over another at close to 100% accuracy is to undergo Pre-Implantation Genetic Screening (PGS). PGS uses a DNA-binding technique to determine if there are a correct number of chromosomes in the embryo at the time of IVF. To complete this screening, embryos on Day 3 of culture (5-10 cells) undergo a biopsy to remove a single cell. The rest of the embryo remains in culture in the IVF laboratory. The removed cells are analyzed for the correct number of chromosomes. Currently, PFC with its cytogenetic partner, Genetics and IVF Institue screen embryos for 3-12 chromosomes. This screening is called “aneuploidy screening.” We allow our patients to know and select the sex of their normal embryos for transfer if they so wish.

Although IVF with PGS is the most effective method for sex selection, it is certainly the most expensive and there is no absolute guarantee that the transfer of the screened embryos will result in pregnancy. A PFC physician can best discuss the odds of success, based on the woman’s age and the couple’s history of childbirth.

Many couples undergoing PGS are doing so to screen for specific genetic defects or are specifically undergoing sex selection because of their risks of having a genetic disease that only affects males (X-linked diseases).

On the other hand, PGS for elective sex selection, either for “family balancing” or even for having a first child of a particular sex poses difficult ethical issues. Just because we have the ability to choose the sex of a child, should we? What will the couple do with normal embryos of the undesired sex? At PFC, we do not encourage PGS for elective sex selection. However, if a couple is undergoing IVF and wishes to undergo aneuploidy screening, we do allow them to select to transfer embryos by sex. We encourage all patients to consider donating excess embryos of the undesired sex for adoption by other couples.

Women or couples interested in this procedure should discuss it with their Reproductive Endocrinologist. At PFC, we also refer our PGS patients for a special genetic counseling session at California Pacific Medical Center in preparation for this process.

Carolyn Givens, M.D. was the first in San Francisco to successfully initiate a pregnancy using intracytoplasmic sperm injection (ICSI). She currently co-directs the Bay Area Pre-Implantation Genetic Diagnosis Program (PGD) and is director of PFC’s PGD program.