Researchers in a 2018 study found that shaving or scraping a vial of donor sperm to extend its use led to a reduction in sperm motility and embryo quality, without affecting clinical pregnancy rates.
If you’ve ever used a vial of frozen sperm for IVF before, you may have heard of “shaving” or “scraping” the vial to save some of it for later. This can be a great way to save money, or to reuse a vial if you can’t get another one for whatever reason.
It is exactly as it sounds. The vial of sperm is removed from liquid nitrogen and then scraped to remove a chunk or shaving of it. This is allowed to thaw, while the remaining vial is put back so it can stay frozen. The original sample isn’t kept out very long so any thawing that happens is minimal.
And that’s a good thing, because repeated freeze thaws mean trouble for sperm integrity! Nijs et al. (2001) report that sperm viability and motility are reduced with freezing and thawing. If you’re interested, I have a post on sperm quality that explains everything that goes into healthy sperm!
So while we hope that the original sample isn’t thawed, it is possible that a small amount of it is. This can be a problem with repeatedly removing the original vial for additional scrapings.
But in reality, it’s hard to say, because there really isn’t much research on this topic! I did find one paper however. Baum et al. (2018) looked at about 100 patients who used donor sperm that was previously scraped or completely thawed. This was a retrospective study from a single university medical center.
🔗 Original studies are referenced in this post or within the linked Remembryo posts.
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How did they scrape the sperm for IVF?
Before looking at the results, let’s be clear about how they actually processed the scraped/unscraped samples.
So for a complete (and unscraped) thaw, the vial is warmed at 37*C and then is processed using density gradient centrifugation. This separates out the dead sperm and other nasties from sample and concentrates the motile sperm. This can then be used for IVF/ICSI.
For the scraped samples, a vial was removed from liquid nitrogen and a piece was scraped off into a new tube. The sperm scraping was thawed at room temperature and not processed using density gradient centrifugation (because the sample was too small).
Motility of scraped sperm after repeated scraping
They looked at how the motility of the sperm changed with repeated scrapings. They did this by assessing sperm samples from 10 donors where 2 vials were frozen at the same time.
For the experiment, they removed the first vial and let it thaw completely to analyze motility.
For the repeated scrape analysis, the second vial was removed from liquid nitrogen for scrape #1, then returned back to liquid nitrogen and removed for scrape #2, and so on. They did this four times.
They found that the motility of the sperm was lower with the scraped samples compared to the completely thawed sample (~5-8% vs 37.1%, p<0.001).
What’s interesting is that the motility of the shaved sample didn’t change with repeated scrapings. So scrape #1 had about the same motility as scrape #4.
Since the density gradient centrifugation process can enrich motile sperm, this might explain the difference. The authors also point out that the mechanical force in scraping a sperm sample might compromise the sperm cells and reduce motility.
They should have controlled for this by preparing smaller volumes of unscraped sperm and processed them the same way. That would have controlled for the difference in processing techniques! But they didn’t, so it’s unclear if the effect is due to the density gradient centrifugation.
IVF outcomes of scraped/shaved sperm
The scraped sperm and completely thawed sperm was used for IVF or ICSI. They found no difference in the fertilization rate (71.1% scraped vs 75.0%) or clinical pregnancy rates (9.1% scraped vs 13.1%). They did find that those that used scraped sperm had a significantly lower number of top quality embryos (average of 1.33 vs 1.87, p=0.02).
So there may be a reduction in embryo quality when using scraped sperm, but this didn’t translate into a difference in clinical pregnancies.
Conclusions
Scraping/shaving sperm is a good way to conserve sperm vials for reuse. This can save money, or ensure continued to use the same donor if they become unavailable. This also makes sense for those who are undergoing chemotherapy and have a limited number of vials available.
There may be a reduction in sperm motility and embryo quality, but this doesn’t seem to have an impact on clinical pregnancy rates. However, the study was small so further research is needed.
Reference
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About Embryoman
Embryoman (Sean Lauber) is a former embryologist and the founder of Remembryo, an IVF research and fertility education website. After working in an IVF lab in the US, he returned to Canada and now focuses on making fertility research more accessible. He holds a Master’s in Immunology and launched Remembryo in 2018 to help patients and professionals make sense of IVF research. Sean shares weekly study updates on Facebook, Instagram, and Reddit regularly. He also answers questions on Reddit or in his private Facebook group.
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