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Behind the scenes in the lab

What goes on in the mystical space called the embryology lab? I've tried to answer a few questions here - but I would love to hear if you have more!

Where are my eggs?

Once your eggs are retrieved at your egg collection they are taken into the lab where the embryologists take care of them. It's really important to keep them warm (37 degrees - same as in your body) and to keep the pH right (thats the acid/alkaline balance). Embryologists need to make sure that the egg has all of the nutrients that it needs and doesn't get 'stressed' at this stage - these first 24 hours can have a big impact on how the embryo (if the egg fertilises) goes on to divide and compact and do all the next things it needs to. So looking after your eggs at this point is really critical. Small changes in the environment at this stage cause stress to the egg that might not be seen until after day 3.

When I used to work for Vitrolife, one of the services we offered was to help clinics to improve their *blastulation rates and *implantation rates (these are both measures of success for an IVF lab). The embryo (later) relies on the energy sources of the egg and the egg's genetics (genome) right through to day 3, so making sure everything is right in these first 24 hours was one of the very first things we looked at when doing lab inspections.

How do they wash the sperm?

An ejaculate actually contains more 'other things' than actual sperm. The sperm that come from the epididymus are joined by lots of other fluid on the way from the tests to the outside world and the resulting fluid contains lots of things that would be naturally filtered out by the process of the sperm making their way from the vagina up to the fallopian tubes where the egg will be waiting to be fertilised (the sperm actually need to be there before the egg, the egg doesn't like to wait!).

So, when we are doing the fertilisation in the lab, we need to wash all that other stuff away so that we are left with the 'cleanest' sample we can get. This doesn't mean that the sperm are dirty, it just means we want to get rid of all the other stuff.

The raw ejaculate is usually placed into a test-tube on top of whats called a 'gradient' - a special liquid filled with a kind of silicon, and then placed in a centrifuge. The centrifuge spins really fast and the smallest heaviest things sink to the bottom due to centrifugal force - thats the sperm that have a head and a tail and chromosomes etc

All the 'other' bits can't fit past the silicone particles. After it's been in the centrifuge, the embryologist can slide their pipette down to the bottom of the tube and suck out the 'pellet' at the bottom and then place that into some clean fluid (we call it 'culture media'). It gets washed through that 'media' at least once, but sometimes twice, and what we are left with at the end is mostly culture media with sperm in it which can then be used for either Standard IVF or ICSI.

What does an incubator look like?

Incubators vary from lab to lab. The main and most important thing is that they are a closed environment where the temperature and the gas levels remain as constant as possible. A very specific mix of Oxygen, Carbon Dioxide and Nitrogen (triple gas) gases are pumped into the incubator, which is what keeps the pH at the right levels, and the temperature is maintained very closely at 37 degrees. Any variations of these two parameters cause stress to the eggs and to the embryos.

Incubators can be big boxes that sit up on a bench a bit like a bar fridge, or they might be smaller and look more like a toaster. They might just have space for dishes, or room for test tubes as well, they might even have a camera installed so that the embryologists can watch a video of the growth of the embryo without having to open to incubator.

The main thing is that the environment is right, and is constant and is disturbed as little as possible.

How do they handle our eggs and sperm and embryos without hurting them?

This can be tricky, and for this bit these days embryologists rely heavily on external companies to make tools for them. This means that the lab has to rely on the quality control systems in place at the external company. Even the tiniest tiniest difference from the specifications can mean that an egg or an embryo doesn't survive. There are SOO many specifications, that it would be impossible to go into here, but size is obviously one of the main ones.

Just some of the micromanipulation pipettes required in the embryology lab

When I was working in the lab, we made most of the pipettes ourselves by pulling glass over a flame. Can you remember the pasteur pipettes you got to use in biology at school?? we used those, but they were WAYYYYYY too big for eggs and embryos and sperm, so we had to make them smaller by holding the pipette over a flame and pulling it gently to make it thinner. It was definitely an art to get exactly the right size, and one that I got better with over time - lots of glass ended up in the sharps container I can tell you!! 😂

We then put a rubber 'bulb' over the big open end and by squeezing and releasing the bulb, we could 'suck' and 'blow' through the smaller end of the pipette.

Before I started working in the lab, embryologists used to use a special fitting on the end of the pipette and then actually suck and blow through the pipette using their mouth (!!!) this is obviously not allowed anymore for health reasons, but was by far and away the most controlled way of moving eggs and embryos around.

These days, most pipettes are made by robots and purchased by the lab in the particular sizes necessary.

Do you Really get to wear PJs all day??

I don't anymore sadly😥😂😂

But embryologists do!!

*Blastulation rate is:

The number of blastocysts formed / fertilised eggs

or sometimes:

The number of blastocysts formed / day 3 embryos

*Implantation rate is:

The Number of heartbeats seen at ultrasound / number of embryos transferred


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