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How many eggs reach blastocyst stage of an embryo?

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6 fertility expert(s) answered this question

Answer from: Saghar Kasiri, Clinical Embryologist

Embryologist, Director of European Operations
Cryos International
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Nowadays with good technology that we have in the lab, we can develop a higher number of blastocysts from the number of fertilized eggs that we have. In the past we could develop the embryos to day 3. In the last few years it has been possible to develop them easily to day 5. It all depends on the quality of embryo on Day 3 that we have.
We expect at least 50% of embryos that are of good quality to go to blastocyst stage of Day 5 and getting to blastocyst stage is very important because that is one stage closer for us to know if we could hopefully achieve pregnancy from that IVF.

 

Answer from: Andrea Sánchez Freire

Senior Embryologist
ReproMed Ireland
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Well, depends on the case, depends as well the age of the patient, the previous IVF failures, is it the first cycle or not. Some studies say that a normal percentage like 50-60% of the embryos reach the blastocyst stage but this depends on a lot of factors like the quality of the sperm, the quality of the eggs.

Answer from: Nurit Winkler

Gynaecologist, Co-Onwer and Co-Founder at Los Angeles Reproductive Center
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Something to remember in the process of IVF and egg donation, the number tends to go down a lot, for example, let’s say we have an egg donor from whom we have extracted 20 eggs. From those 20 eggs, probably about 15 or 16 are actually usable. Of the 16, we fertilise them and probably about 13 or 14 will become embryo’s. Of those embryo’s, we keep them in the lab to see which will keep developing to the final stage called day 5 or blast embryo’s, we lose around 50 percent of them so now we are down to around 7 embryo’s.
Of the seven embryo’s when we check them for chromosomes, there are only around 4 abnormal ones. So you can see how on an average of around 20 retrieved eggs you end up with around 4 or 5 usable embryo’s.

Answer from: George Koustas, DR

Embryologist, Director of Embryology and Quality Manager
Agora Clinic
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That’s another million dollar question. It depends on many factors: the patient’s age, sperm quality and reason of infertility. In theory around 50 to 60% of embryos will reach the blastocyst stage and around 30% will be good quality blastocysts meaning A or B that they can be transferred or frozen.

Answer from: Raquel Arévalo Jiménez, Biologist with a Master degree in Human Fertility

Embryologist, Junior Embriologist
ReproMed Ireland
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After the egg collection we check which of the oocytes are mature and we will perform IVF techniques on those oocytes and the next morning, we check if these eggs have fertilized, so we can have different results in the fertilization rate. Sometimes the egg quality is very poor, we don’t have a very good fertilization results but even though, we have to focus in the embryos that we have and if we have three oocytes fertilized out of four – this is a very very good result; if we have three of six it’s also 50% so we consider 50% a good result of fertilization and if we have three oocytes that have fertilized comparing with more eggs that we collect in the in the egg collection, we have to to to study why basically. So it can be a problem of the oocytes (that they can have a poor quality) and we can see this when we do the IVF and we also have to check the sperm parameters and we have to see if this low rate of fertilization is due to the sperm. So the first time that we do a treatment, we don’t know, we don’t really know the result that we are going to obtain. Some patients have a very good fertilisation rate and some other patients don’t have a good fertilisation rate even if it’s the second or the third treatment. So it’s very important to see the quality of the gametes and it will influence a lot to the third result. So if we have three oocytes that have fertilized, the best thing to do is to focus on these three and we have three options to have embryos with good quality so we have to be positive and you never know if they are going to be the best embryo. Sometimes, even if you have only three eggs, perhaps three of them are going to be of good quality and perhaps other people have ten eggs that have fertilized but finally they only have one embryo with good quality. So it’s important to be positive about all the procedures and to wait until Day 5 because we don’t know exactly how this embryo is going to develop until Day 5.

Answer from: Despina Tzanakaki

Senior Embryologist, Director of IVF and Andrology lab at Aretaieio Hospital
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On average about 25% of oocytes collected will reach the blastocyst stage. After oocyte collection, some oocytes will be immature, some of the mature oocytes will not fertilize, some of the fertilized eggs will form cleavage stage embryos and some of the cleavage stage embryos will make it to the blastocyst stage.

About this question:

How many eggs will reach blastocyst stage?

Blastocyst is an embryo at the final stage before transfer to cryopreservation. It is also called a “Day-5” referring to development time. The biggest “drop out” in the number of embryos is expected between days 3 and 5 of development as the male factor is getting involved.

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