Question: is it hard to freeze sperm

Laura Wales answered on 15 Jun 2015:

The process of freezing sperm isn’t all that difficult once you’ve been trained. To do a freeze I would first of all carry out an analysis to see what the quality is – I look at motility (how they are swimming), the concentration (how many there are) and the morphology (shapes).

If it’s a nice normal sample, it’s a case of adding a solution that helps protect the sperm when being frozen and stored at low temperatures. After that, I would transfer the sample into straws (a new meaning of the word for me) – they’re just thin tubes that hold 0.5ml of the sample. Then the straws are put of a machine that’s set up to gradually lower the temperature in stages.. After that the straws can be put straight into liquid nitrogen which is around -196 degrees Celsius.

It’s more difficult when the sample is really poor (ie. if there are hardly any sperm). Quite often patients with some types of cancer have not so good samples – not only are they ill, but they’ve quite often been given medicines which affect the quality of their sperm. In cases like this, sometimes I need to treat the sample in a different way so I get the best possible numbers for storage.

The key stages to get right are:
– Making sure the sample is kept at the right temperature so working reasonably quickly is needed.
– The way I add the solution to protect the sperm is vital as sperm don’t like changes in their environment too much.
– Making sure the machine is set up with the right temperature changes.
– Putting the sample away quickly so it doesn’t thaw.

Oops, just realised how much I’ve typed. Got a bit carried away there. Hope this answers your question 🙂