Embryo Development

Embryo development is the stage before implantation and after fertilization. Whether IVF or ICSI no matter which method is used, the very first step of the embryo development starts with a performed zygote. This step takes approximately 30 hours after pronuclei join to the moment cell division begins. For healthy embryo development, this period has to take place at max. 30 hours.

The next step for healthy embryo development is dividing cells at the right time. By 48 hours (on the 2nd day) following the egg retrieval,  collected embryos should be divided into 2 to 4 cells. By 72 hours (on the 3rd day) it’s expected to reach at least 6 cells.

Embryo Development Stages 

Embryo development IVF has 3 stages to go forward before implantation. The first few days of development are called “Cleavage”. The cleavage stage allows monitoring the number of divisions and degree of fragmentation. 

The embryo development cleavage-stage lasts for about 3 days. Through this time your doctor will examine the number of cell divisions and degree of fragmentation. The degree of fragmentation is important to achieve healthy embryo development. It is preferred to have little or no fragmentation. If the embryos have more than 25% fragmentation then the implantation chance will be below. 

The number of cell divisions is another parameter for achieving healthy embryo development. At the end of Day 3, the embryo has to be at least 6 ideally 8 distinct cells. The cells in cleavage stage embryos are known as blastomeres.

Morula is the 2nd stage of embryo development which starts on the day 4th. Morula is an early-stage embryo consisting of 16 cells. In the morula stage, the cell continues to divide but it’s hard to count the number of the calls anymore.

In the second stage of embryo development, the blastomeres begin to form tight junctions with one another.  This is called compaction and the round shape of the cells turns to a form as mulberry has. This mulberry shape gives the name morula to the embryo. 

The 3rd and last stage before implantation is known as a Blastocyst stage. The blastocyst stage takes place by the fifth or sixth day after fertilization. As Blastocyst starts the formation of junctional complexes between blastomeres will look like a rapidly dividing ball of cells and will give the embryo an outside and inside construction. The inner group of cells will be embryos and the outer group will be the cells that nourish and protect the embryo which means that the embryo is ready to implant. 

Embryo Development After Transfer

After the Blastocyst stage, if everything is alright the individual will be called for the implantation. Embryo development after transfer continues day by day.  It takes 9 days for embryo transfer to complete. After this period the individual’s pregnancy may be detected.

Embryo Development Before Implantation After Transfer 

During the days after a transfer, let’s see what happens to the embryo day by day

1st Day after embryo transfer; the shell hatches and the blastocyst begins to hatch out. It will take 2 days for the blastocyst to complete this hatch-out procedure. 

2nd Day after embryo transfer; As the blastocyst completes to hatch out, it begins to attach itself to the uterus.

3rd Day after embryo transfer; the implantation begins when the blastocyst attaches deeper into the uterine lining. This period will last till the end of day 4. 

5th Day after embryo transfer; the blastocyst implantation is completed and the period of cells turning to placenta and fetus starts. 

6th Day after embryo transfer; as the implantation is completed successfully hCG hormone is going to enter the individual’s blood system. It takes 2 more days for the hCG to reach the ideal level to detect the pregnancy by blood tests. 

On the 9th Day after embryo transfer; hCG levels are now high enough to detect pregnancy using a blood test.