Many patients receiving medical care for infertility will use cryopreserved (frozen) sperm, oocytes and/or embryos at some time during their treatment. Here in the PFC laboratory, we routinely cryopreserve sperm and embryos. We also receive specimens from sperm banks nearly every day. All of these specimens are stored on-site in our secure tanks with continuous monitoring. All specimens are stored in liquid nitrogen at -196ºC. Movement in or out of the tanks only happens when specimens are transferred post freezing or retrieved for thawing or shipping. We store sperm and embryos for our patients for an annual fee as long as we are able to maintain yearly contact with them and the annual storage agreement is renewed.

The shipping of tissues that are frozen and stored at such a low temperature is not easily accomplished. The liquid nitrogen in which they are stored is not toxic in any way, but it is extremely dangerous and can cause serious injury and even death if not handled properly.

In attempting to transport tissues that are normally stored in liquid nitrogen, we have to use a device that will keep the tissues in their same deep frozen state. This is accomplished using a “Dewar” which resembles a large thermos. A Dewar is a vacuum insulated container, mostly filled with an absorbent lining that soaks up liquid nitrogen. The Dewar is “charged” prior to use by filling it with liquid nitrogen over successive days until it will absorb no more. Once saturated, the excess liquid is poured off and the Dewar is then ready for use. Specimens are loaded into the hollow core and they are maintained in their frozen state by the cold nitrogen vapor evaporating from the surrounding absorbent layer. The Dewar holds an appropriate temperature for as long as nitrogen remains inside. Loss of nitrogen by evaporation happens continuously. Typically a fully charged Dewar maintains temperature for between 7 and 30 days depending on its size, how often it is opened and how well it was charged before use. With any Dewar however, loss of refrigeration occurs after a certain period of time, unless more nitrogen is added. In addition, dropping the Dewar or otherwise damaging it in any way can crack the container and this will result in instant failure of the vacuum seal with subsequent loss of nitrogen and thawing of the contents.

When we receive a shipment of sperm from a bank, there is always a risk that the Dewar was damaged or that there was a shipping delay that was longer than the life of the liquid nitrogen in the tank. If the specimens have thawed, typically the sperm bank will replace them at no cost. However, their liability is limited to replacing the sperm, and if you just lost the last 3 vials of your favorite donor, you’ll have to choose a new donor.

Shipping of embryos is a much more risky proposition. Embryos can’t be replaced in the same way that a sperm sample can be replaced, if they can be replaced at all. The major shipping companies such as FEDEX, UPS and DHL will not knowingly accept embryos for transport and therefore would not have any liability for loss. At PFC we discourage shipment of embryos due to the risks involved. We will not ship embryos from our laboratory on your behalf, however you can come and collect your embryos in person and ship them yourself. We will ask you to sign papers releasing us of any liability once the embryos leave our office. We cannot accept any liability for embryos that are being shipped in from elsewhere; it is a practice that we discourage.

If you absolutely must ship embryos, we suggest that you contact a company that has the expertise and the experience to make this type of shipment as safe as possible. Locally, we recommend “Swift Stork Courier” (www.swiftstork.com) who will arrange collection and delivery of the embryos and ensure appropriate and safe handling during transport. For long distance shipments, we put patients in contact with “Kynisi Courier Systems” (email: kosta@kynisi.com), a company based in the UK that specializes in shipping embryos. If you want to send your embryos from

San Francisco to Detroit, or Dublin or Dubai, Kynisi is the only company we know that can get embryos on airplanes without being x-rayed in security. They also get advance clearance to make sure that embryos don’t get delayed in customs as they cross international borders. Kynisi can also arrange for an embryologist to travel with your embryos, and they can organize for the embryos to travel in the passenger cabin of the aircraft, as opposed to being thrown in the luggage compartment with the other cargo. This is important, as a Dewar left lying on its side will lose nitrogen more rapidly than when upright. Kynisi’s services aren’t inexpensive, but considering that the embryos are priceless, there really isn’t a good alternative.

For those patients considering moving their frozen tissues to a facility that offers long-term storage at reasonable costs, we recommend “ReproTech” (www.reprot.com) in Reno, NV. ReproTech is experienced and knowledgeable, and gives great customer service. They too can arrange safe movement of your tissue from us to them, and back again with minimal inconvenience. They often take the extra precaution with embryos by splitting them into 2 groups that are then shipped separately. ReproTech shares the PFC philosophy of thinking of embryos as irreplaceable, and they take every known precaution to ensure a safe and efficient shipment. However, despite the good work of ReproTech, Kynisis and others, I recommend that you do not ship your embryos. The risks are too great.

Joe Conaghan, PhD

Tags: Egg Freezing, Embryo Freezing, Fertility Preservation, Lab, Resources

This entry was posted on Wednesday, June 6th, 2007 at 4:42 pm and is filed under Science Pulse. 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.