The IVF process

What do fertility clinicians and scientists do with eggs and sperm, in order to make a baby?
23 July 2018

Interview with 

Adam Burnley, Bourn Hall Clinic Cambridge


What actually happens in the lab in a fertility clinic? Chris Smith met embryologist Adam Burnley at Bourn Hall, the clinic set up by Bob Edwards, Jean Purdy and Patrick Steptoe following their success creating Louise Brown. Adam explained the IVF process at the clinic; and for all cases, his first job is to assess fitness of the father’s sperm...

Adam - We’re looking for numbers of sperm, how well those sperm are moving, and the sort of abnormalities within the sperm.

Chris - I’m looking at the computer screen. That’s someone’s sample as seen down the microscope. Talk me through what’s on there.

Adam - What the software associated with this equipment does is identify the sperm heads. So anything of that size and shape it will track individually and it will work out how quickly that sperm is moving forwards, whether it’s moving at all, and will give us a precise number of sperm so that we can base our treatment recommendation on that, on the results.

Chris - How do you then make a judgement about the most effective way to treat that patient based on what you see here?

Adam - We take what the World Health Organisation call a normal sample parameters, so a certain number of sperm, the type of motility. And if the sperm parameters are above those, or what we would call a normal sample, we might just want to mix sperm with eggs and let the sperm fertilise those eggs on their own. If the parameters fall lower than those, we might decide that we need to inject sperm individually into eggs to enable those to fertilise and to create embryos.

Chris - What happens next?

Adam - We’ll go through to the lab and where the theatres are and I’ll try and explain what happens.

The female patient will need some preparation before they come in for an operation to harvest any eggs, and what that involves is stimulating the patient with fertility drugs which makes them hopefully produce more than the usual one egg per cycle.

Chris - And that happens in here? This looks a bit like an operating theatre.

Adam - We have an anaesthetic machine if necessary. A scanning machine so that when the surgeon’s doing the collection they can see the patients ovaries on a screen and therefore they can use a metal needle attached to a probe to suck out the eggs from each of the follicles. And depending on how many follicles that patient has grown in response to the fertility drugs, hopefully we should collect a corresponding number of eggs from those follicles.

Chris - How many eggs do you get from someone for each cycle like that?

Adam - The average number of eggs that we collect from patients is about ten, but some patients will get one egg collected, some patients will stimulate much more and get 30 or 40 eggs collected. And as the doctor is doing the egg collection we’ll let them know how many eggs they’re collecting. They’re put into a culture media which keeps them at the optimal conditions until we’re ready to do either IVF or the injection of sperm.

Chris - If you decide to go down the route of what they call ICSI (Intracytoplasmic Sperm Injection), which is why it gets called ICSI I’m guessing…

Adam - Yes.

Chris - ... where you are literally injecting a sperm into an egg. What happens then and where do you do that?

Adam - Do you want to come through here and I’ll show you where we perform that procedure.

What we’ll have to do before the ICSI procedure is to assess how many of the patient’s eggs are suitable for that procedure, and usually we find 80 percent will be. What we then do is, under a high power magnification, we have to select an individual sperm, immobilise that sperm by hitting it on the back of the neck with a needle, and we then inject that sperm into each of the suitable eggs. We hope that about 70 percent of those eggs that have that procedure will fertilise.

Chris - And hopefully, by that stage, the person has a reasonable prospect of getting a fertilised egg. What do you do then?

Adam - We’ll want to culture those and grow them for a few days until the embryo reaches the appropriate stage for us to select the most likely one that we think is going to implant.

Chris - So it takes about five days before you’re in a position to put the developing embryo back into the woman?

Adam - Yes, that’s right. The embryo when it gets to about day five become what we call a blastocyst, so its cells have different functions within the embryo, and the embryo needs to do that in order to implant.

Chris - This is one of the incubators: it’s got a series of drawers on the top I can see you’ve been putting some of the dishes, which have got the developing embryos, in. The amazing thing is there is a huge screen on here and we can see embryos developing. I can see cells dividing and you’re watching these things in almost real time.

Adam - Yeah, that’s right. This is relatively new technology in that in normal incubator conditions you would look at your embryos once a day; whereas this is taking a picture of the embryo every five minutes so we can review its development to see whether the embryo’s followed the right patterns of development.

Chris - This one’s just gone from 1 cell, to 2 cells, 4, now we’re at 8, 16, that’s amazing!

Adam - Yeah.

Chris - That’s a human developing?

Adam - Yeah. And to see it happen in that time lapse quick play is an amazing thing really. You can watch five days of development in two minutes.

Chris -  I wouldn’t get any work done if I worked in this lab because I’d be stuck here watching this.

Adam - An amazing bit of technology really.

Chris - You would be able to tell from those pictures what one looks promising and what one’s not going to make the grade, can you?

Adam - On day five, we look at all the embryos, see which one has developed to the best stage, but then we can review the footage of that embryo developing and possibly deselect or select embryos to transfer based on that information.

Chris - This person here’s got quite a lot of embryos cooking. You’re going to be able to put how many back into that person and what do you do with the rest of them?

Adam -  Okay. Well, the law allows us to put either one or two embryos back depending on their circumstances. If the patient then has other embryos which have reached the right stage we could possibly freeze surplus embryos, which means the person could come back if they’re not successful.

Chris - How do you get that back into the woman?

Adam - We have to pick the embryo up in a really tiny amount of culture media in what we call a transfer catheter, a sterile floppy plastic tube which is attached to a small syringe. Take it through to the surgeon who has the patient prepared for the transfer and he will feed the soft catheter through the cervix directly into the uterus, press the plunger on the syringe, and the embryo or embryos will be deposited in the uterus in the right place.

Chris - Does the lady have to lay there with her legs in the air for hours on end?

Adam - Not any more. It used to happen but not for a long time.

Chris - You used to do that?

Adam - Yeah. A patient would sit for three or four hours sometimes either in bed or with their legs up in the air. The fear being that the embryos would drop out.

Chris - Drop out?

Adam - Yeah. But a lot of studies have shown that it is absolutely not necessary. The embryo transfer procedure means you can walk down to theatre, have your transfer. The whole process takes about 15 minutes and then you can go home and resume your normal life and hope for the best.

Chris - And what’s the soonest you would know if it’s worked?

Adam - Really the earliest is about a day 18 home pregnancy test all the patients do.


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