Dr. Tim Dineen Discusses his Role as Leading Embryologist

I am head of the laboratory at Waterstone Clinic. My main role involves the fertilisation of eggs through in vitro fertilisation (IVF). In traditional IVF, with normal sperm count and motile sperm, we add the sperm to eggs and let nature take its course. We then check the eggs have been fertilised the following day.

When dealing with low sperm numbers or poor motility there is a higher chance fertilisation will not occur, so we use intracytoplasmic sperm injection (ICSI). This allows us to inject a single sperm into each egg. Selecting the eggs for ICSI is straightforward in that we only inject mature eggs, as an immature one does not have the potential to fertilise. The sperm, which has already gone through a selection process when it was prepared, is added to a viscous medium to slow it down and capture a healthy sperm.

We use high-powered microscopes with micro-manipulators to keep the egg in place while the sperm is injected — the eggs are smaller than a speck of dust.

ICSI has revolutionised IVF treatment as it allows us to overcome many forms of male fertility problems. Even when there is no sperm in the ejaculate, it’s not the end of the line: we can perform a biopsy to retrieve sperm from the testes, and use that to create embryos.

This is one of only two IVF clinics in Ireland authorised to carry out embryo biopsy to facilitate preimplantation genetic diagnosis (PGD) and preimplantation genetic screening (PGS). For PGD, this gives a couple the option of trying to reduce the risk of passing on a genetic condition.

We only recommend PGD treatment for couples where a life-limiting condition has been identified and will be passed on to their children. We do not use the treatment for “designer babies”.

There are a number of rare single-gene conditions we get inquiries about, but the one we are asked to test for most in relation to PGD is cystic fibrosis. Ireland has one of the highest carrier rates of cystic fibrosis in the world.

Our first couple for PGD involved a man affected with cystic fibrosis whose partner was a carrier. They had a one in two chance of every pregnancy being affected with the disease. When a couple is faced with this tough decision, they have a number of choices, one of which is to carry out PGD. Alternatively, they could pursue a treatment cycle with donor sperm.

In this case, we had to check if the male was producing sperm: one of the features of cystic fibrosis is that there is no sperm in the ejaculate. Fortunately there was sperm, so we fertilised a number of eggs, and on day three removed one cell from each embryo and sent them to a genetics testing lab in the UK. Forty-eight hours later we got the results: there were five embryos suitable for transfer. This meant that while all the embryos were cystic fibrosis carriers, they would not be affected by the condition.

That couple had a healthy baby girl — the ultimate measure of success in PGD.