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Embryo culture till the Day 5 is as it says. We keep the embryos so, from your egg collection, we will mix the sperm and the eggs the same day, we’ll check them the next morning or the first signs of fertilization and then they’ll go into a specialized incubator (either a normal conventional incubator or a time-lapse incubator) and they’ll be left there until Day 5 and that allows us to go monitor the embryo and it’s different checkpoints. So on day one which is the day after your egg collection, we just expect to see normal fertilization, at day two we expect the embryos to be between two and four cells, day three around the eight cell mark, day four we don’t really check them (it’s such a large transition day). The first three days are down to the egg mainly and exclusively down to that form. Sort of between day two and day three, the sperm factor comes into play. The sperm has to flick a switch inside the embryo – called the embryonic genome and that allows the embryo then to grow onto a blastocyst by Day 5 so, the blastocyst is then more of a 120 cells, it’s created in a completely different way.
It’s a bit of a strange way of thinking about a blastocyst but if you think of it like a football what will gradually happen is that football inflates and as it inflates we can tell the quality a lot, more accurately. So we see the inner cell mass which is the group of big chunky cells in the middle that goes on to make the baby and then the cells surrounding the outside of the football are called the trophectoderm what that goes on to make the placenta and what we like to see in those is that nice cobbled street effect. So if we can see nice, big, chunky inner cell mass cells, a nice cobbold street trophectoderm – that is a good quality blastocyst. Now, you can get all sorts of different combinations and setups of that blastocyst. It could be that when we check them on Day 5, they’re still at that deflated stage and we can’t really tell what they’re doing and it’s just downs that allows us the best embryo selection because what we might see sometimes on Day 3 is you might have several really nice beautiful eight cell embryos and maybe a not so good six cell but by the time you cultivate them onto Day 5, that embryonic genome switch has been flicked and the best embryos that you saw on Day 3 may not necessarily be the best embryos you see on Day 5 and so it’s about deselecting and selecting the best ones again.
Answer from:
Over the last years there had been a gradual shift from culturing on Day 3 to culturing to Day 5 and this was achieved mainly because of the advances in our cultural media and our incubator systems. Thanks to this new development, we are able to monitor our embryos for longer periods and monitor special the transition from Day 3 to Day 5 which is a very important period for the embryo development since this is the period where the sperm factor is activated and the embryo will need to prove its fitness by supporting more demanding steps of its development which involves the increasing the mitotic divisions and increasing the metabolic activity. So it’s a new method that improves embryo selection efficiency when culturing to Day 5.
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Embryo culture to Day 5 has become a very good tool because A) it is a selection method that does not involve us throwing away embryos. It is only suitable and recommended for people who have more embryos than intend to have put back in one cycle. So if a patient has produced 15 eggs and she’s having eggs usually out of those 15 the 12 will be mature because only mature eggs are injected with ICSI, out of the 12 on average 8 or 9 will fertilize. So starting off with 9 fertilized eggs on Day 3, you could have maybe 6 or 7 of these fertilized eggs making embryos. If you have 7, you don’t know which one to choose to go back and also if you decided to take one on Day 3, chances of leading to a baby would be 25% but if you allow the survival of the fittest by keeping them for two days – not all of them may reach that stage. So the 5 that will make it to blastocyst, you choose one of them and put back and the other will be in the freezer giving you few additional lifelines. Some patients will have only 2 eggs produced and 2 embryos on Day 2 or Day 3 they say “why can’t we have them for Day 5” – there is nothing to be gained because for your circumstances having them in is better than out because yes the environment outside the body has improved significantly but we can’t look the patient in the eye and we say it is as good as outside.
Answer from:
Blastocyst culture involves keeping the embryos in the lab for a few days in special conditions up until day five or day six of development following the egg collection. On the fifth day of the embryo development, the embryos become blastocysts. The embryos at this stage should have a group of cells that is called inner cell mass that will make the baby, hopefully and then a group of cells around that will make the placenta. On day five the embryos are assessed based on their expansion and how those two groups of cells look under the microscope.
