Frozen or Fresh?

Critics Abound

Cryopreservation, the act of freezing sperm, eggs, or embryos as a means of preservation has been around for quite a while. That doesn't mean that cryopreservation isn't without its critics. Some criticize the freezing of embryos and sperm because of moral or ethical issues, while others question whether the acts of freezing and thawing may harm the quality of these reproductive necessities, leading to possible birth defects.

Now, a Mayo Clinic study shows that couples undergoing in vitro fertilization (IVF) have the same incidence of healthy pregnancies and deliveries regardless of whether the sperm used in the procedure is fresh or frozen. These results were presented at an annual scientific meeting of the American Urological Association in San Francisco. According to Alan Thornhill, Ph.D., senior author of the study and the director of the Mayo Clinic in vitro fertilization laboratory, there had been a concern that frozen sperm could be responsible for reduced birth rates. The results of this study prove that such concern is unwarranted.

The process of in vitro fertilization begins by stimulating ovulation by means of fertility drugs. This stimulation causes the woman to produce more eggs than is usual. Once the eggs mature, they are retrieved from the ovaries and exposed to sperm for fertilization. The availability of sperm on the day of egg retrieval is crucial to the procedure's success.

After some 2-5 days, the embryos (fertilized eggs) are ready to be transferred to the uterus. In this study, researchers froze sperm samples in the event that a fresh sample would not be available on the day of the egg retrieval. Researchers then calculated the rate of live babies born per single egg retrieval. The cumulative live birth rate for cycles using the fresh sperm was 51.6% while the frozen sperm produced live births per cycle at a rate of 53.1%

These impressive statistics were collected at the Mayo Clinic from between 1993-2003 with fresh sperm used in 1,580 cycles and the frozen sperm in 309 cycles. The Mayo Clinic freezes sperm samples as part of the in vitro process in the event that a fresh sample will not be available on the required day. The effectiveness of the fresh versus frozen sperm was calculated by determining that at least one baby was born from a single egg retrieval from the mother.

Dr. Thornhill explains that Mayo clinic doctors prefer the use of fresh sperm where possible because the number of sperm and sperm motility are reduced after freezing and thawing. However, if fresh sperm isn't available, due to illness, travel, or other circumstances, couples need not worry about the effectiveness and safety of using frozen sperm.

Don't Worry, Be Happy

"The in vitro process is long and can be difficult -- emotionally, physically and financially," comments Dr. Thornhill. "These results make the process just a little bit easier."

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