How Long Does Frozen Sperm Last?
Ever wondered how long frozen sperm lasts? Learn more with guest blogger, Christina Barnes, RN
So far, no limit has been established for how long human semen can be frozen when maintained and stored in appropriate liquid nitrogen storage. Fairfax Cryobank has maintained cryopreserved human semen in storage for over 30 years, and semen stored for 19 years has been used to achieve a pregnancy.
How are sperm frozen and stored?
I spoke with Chauntae Nichols, Laboratories Manager at Fairfax Cryobank, about their sperm storage process. Chauntae has been with Fairfax Cryobank for 16 years, starting as a laboratory technician and working her way up to her current role. As Laboratories Manager she oversees all 6 of Fairfax Cryobank’s laboratories. Her first-hand experience handling samples in the lab and broad knowledge of how the labs function makes her the perfect person to explain this process.
First, the sperm sample must be collected. The easiest and least invasive way to collect sperm is through ejaculation. If an individual is unable to ejaculate or there is no sperm in the ejaculate, then sperm can be extracted by testicular sperm aspiration or extraction. These procedures involve removing sperm from the testicle with a needle or incision; the type of extraction procedure needed would be determined by an individual’s healthcare provider.
Once the sample is collected, it is placed into a small plastic vial. The vial is labeled with the individual’s name, donor number (if applicable), and the date it was processed. These vials are then stored in large tanks organized by coded partitions. Chauntae describes the tanks as “a very large isolated thermos” kept very, very cold by liquid nitrogen. Amazingly, no electricity is required to keep the tanks cold since the liquid nitrogen does all the cooling work on its own. This is great news for all that frozen sperm during a power outage: “no power, no problem” says Chauntae. Every tank has its temperature constantly monitored by battery-operated probes. Everything is tested weekly, and any issues are immediately addressed and fixed.
So how does freezing sperm actually work to keep the sperm alive? “The cool thing about ultracold temperatures is that it freezes cells in time,” says Chauntae. “As long as the sperm is kept in this deep freeze state, the sperm can be stored forever. At my location in Minnesota, we have sperm from the 70s still frozen.” Once it’s time to use the sperm, it thaws in as little as 10 minutes.
Will using sperm that has been stored longer make it harder to get pregnant?
Short answer: No. A recent study in Fertility and Sterility examined the clinical outcomes (pregnancy, miscarriage, live birth) of 119,558 semen specimens at a sperm bank in China. The study looked at these outcomes in sperm that had been stored for up to 15 years. They found that there were no differences in the rates of pregnancies, miscarriages, and live births when using sperm with different storage times. They concluded that freezing sperm for at least 15 years will not make it harder for a woman to get pregnant. Few scientific studies have looked at stored sperm over 15 years, but there are many cases of women becoming pregnant with healthy babies using sperm stored for 20+ years.
How much of the sperm sample survives after it is thawed?
The longer sperm is frozen, the lower the survival rate of the sperm once it is thawed. In other words, if you thaw a sperm sample that has been frozen for 12 years, you will have a lower percentage of functional sperm when compared to a sample that has only been frozen for 2 years. However, the survival rates are still high enough to have enough functional sperm in a sample to cause pregnancy.
The study from Fertility and Sterility that we discussed in the last section also looked at the survival rates of sperm across these 119,558 semen samples. They measured the amount of living sperm in the sample after it had been thawed and compared it to the amount of living sperm in a pre-frozen sample.
|Length of Sperm Storage||Frozen-Thaw Survival Rate %|
|6 months to 5 years||85%|
|6 years to 10 years||82%|
|11 years to 15 years||74%|
If those numbers are confusing, don’t worry; the takeaway is that the majority of sperm survive after being frozen for at least 15 years. That’s pretty incredible.
To recap: sperm can stay frozen for a very long time (possibly forever), using this sperm will not reduce the chance of pregnancy, and a lot of the sperm will survive after thawing.
Huang, C., Lei, L., Wu, H., Gan, R., Yuan, X., Fan, L., & Zhu, W. (2019). Long-term cryostorage of semen in a human sperm bank does not affect clinical outcomes. Fertility and Sterility, 112(4), 663-669.
To learn more about the sperm from Fairfax Cryobank and quality standards visit our Specimen Information resource page.