The Laboratory Phase

What happens with the eggs in the time between the egg aspiration and the egg transfer?

The egg aspiration

In order for us to be able to fertilize the egg in the laboratory, the eggs must be aspired from the woman and the man must hand in a sperm sample. At the egg aspiration, a needle guided by ultrasound is moved through the vagina and the point of the needle is inserted through the vaginal wall and into the follicles. You will receive an anaesthetic beforehand and most women cannot feel anything. The egg aspiration normally takes approximately 10-15 minutes. The fluid in the follicle that contains the eggs is thus sucked into the syringe and the fluid is handed over to the laboratory assistant who right away examines the fluid in the laboratory. Using a microscope, it is possible to count the number of aspired eggs. Usually 80% of the follicles contain eggs.

The eggs are then moved into a small bowl filled with nutrient fluid and placed in a cupboard called an incubator at 37o, that is, at body temperature.

The fertilization

Approximately 0-4 hours after the egg aspiration the eggs must be fertilized. This corresponds to the time that the eggs would meet the sperm cells in the Fallopian tube under natural circumstances.

Just before the egg aspiration the man hands in a sperm sample. This sample is prepared and analysed in the laboratory. We prepare the sperm in order to ensure that only the "good" sperm is being used in the fertilization. We analyse the sperm in order to see if there is a sufficient number of sperm cells to perform a normal in vitro fertilization. Should there not be enough good sperm cells, we can make use of the ICSI method - also called micro insemination.

At normal in vitro fertilization, the prepared sperm is added to the eggs. We add approximately 50.000 - 100.000 sperm cells to every egg. The eggs and the sperm cells (by now in the same container) are put back into the incubator, and during the next 16-18 hours we will be able to see whether the eggs have been fertilized. Approximately 24 hours later, we will attend to the eggs again and we count how many have divided.

Cultivation of the eggs

The fertilized egg is also called an embryo. The embryo is now beginning to divide, first into a two-cell, then into a four-cell and so on. After 2-3 days the embryos are ready to be transferred to the uterus or be frozen down for later use.

Unfortunately, not all eggs divide. An average of 60% of all the aspired eggs divide. With 5-10% of all couples, however, no eggs divide.

Good eggs

Before the eggs are transferred to the uterus, they are examined by the laboratory assistant. How many have divided? Are the eggs good? On this basis, the doctors and the laboratory assistants decide which eggs and how many eggs that will be transferred to the uterus.

The considerations that contribute to this decision are: the woman's age, previous in vitro fertilizations, number of eggs that have divided and if the eggs look good.

The more eggs that are transferred, the better the chances of pregnancy. BUT the probability of a twin pregnancy or triplet pregnancy also increases. Therefore it is important to make up your mind about how many eggs you want to have transferred into the uterus. Of course, you are always welcome to consult the doctor.

Many couples choose to have a single egg transferred, because we have better results with a single embryo today than earlier. Being pregnant with twins or triplets is not risk-free. Twins are born an average of 1 month too early and triplets approximately 7 weeks too early.

Egg transfer

The egg transfer itself is very simple and doesn't hurt. The laboratory assistant has placed the embryo/s in a thin plastic catheter before the procedure. The doctor receives the catheter and moves it through the cervical canal and into the uterus where the embryo is placed.

Freezing the embryos

If you are so fortunate that more than the fertilized egg that has been transferred to the uterus have divided, you can choose to have them frozen for later use - either for a brother or sister, or if pregnancy doesn't occur. This procedure means that the woman can avoid hormone treatment again. Only the best quality eggs can tolerate being frozen down.


Read more about micro insemination (ICSI)



Progress with PGD for Sickle Cell prevention
Studies in Denmark and Belgium.

Good IVF success rates after single embryo transfers
Transferring one IVF embryo, followed by a second, is almost as likely to result in a pregnancy as transferring two at a time.

IUI workshop
At University of Maiduguri Teaching Hospital

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