What is the required number of embryos for a successful Invitro?

What is the required number of embryos for successful InVitro fertilization ?

In 2020, the best in vitro fertilization programs in the world do three things. First, they grow the embryos until they reach the blastocyst stage, which usually takes 5 to 7 days. Second, all embryos are frozen for so-called frozen transfer, and third, genetic tests are performed on the embryos, especially if they are obtained from older women.

Successful InVitro fertilization?

In vitro specialists use drugs to stimulate the development of many follicles or eggs in the hope of creating more embryos. This is necessary because there is a significant reduction in their number as you go through the various stages of treatment. Your doctor may see 20 follicles on ultrasound, but only get 15 eggs. And not all eggs can be mature.

Let’s say you get 10 mature eggs. These 10 eggs are injected with 10 sperm and the fertilization is usually 70%, ie we have seven fertilized eggs. Some of these embryos may never develop. Some may develop in a few days and then stop. For these reasons, not everyone reaches the blastocyst stage. It is normal for at least 30-40% of them to reach this last stage of development. Will it be enough? The answer is maybe yes, but maybe no. The problem is that some of these embryos may be abnormal…

How does age affect the development of normal embryos ?

Abnormal embryos may have too many chromosomes, too few or other abnormalities. The older the mother, for example, the greater the risk of having abnormal embryos. In fact, the chances of an embryo being normal decrease with each passing year.

Let’s look at some real-world situations.

A woman under the age of 35 who has had only one embryo that has reached the blastocyst stage, has about a 32% chance that the embryo is normal. If she has managed to make two blastocysts, then there is a 64% chance that at least one of them will be normal. For three embryos this is 88%, and for four or more there is a 98% chance of having at least one normal embryo. At age 41, if you have had four embryos that have reached the blastocyst stage, which is not easy for a 41-year-old woman, there is only a 60% chance that at least one of them is normal. Think about it in the opposite direction. At age 41, you may have four microscopic blastocysts, but there is a 40% risk that they will all be genetically abnormal. At age 31, there is a 2% risk that all four blastocysts will be abnormal.

In conclusion

The truth is that although the numbers in Invitro treatment are of great importance, there is no way to definitely define strict patterns. Each case is individual, but it is important for each woman to be familiar with the laws and what chances she has in the first place, taking into account the age at which in vitro fertilization is performed.

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