Table of Content
Introduction to Embryo Development
Embryo development day by day involves labyrinthine coordination of molecular, cellular, and tissue-level processes that have to occur in line with strict schedules of time and placement. Whereas the gestation periods of mammals vary greatly (from a pair of weeks in some rodents to just about a couple of years in elephants), the sequence of organic process events and their molecular underpinnings is comparable from species to species. This biological correspondence explains extrapolating the results obtained in animal studies to humans. Despite this natural consistency in the case of embryos, there are variations among species concerning several aspects of physiological conditions. It is these variations that are explored in risk assessment.
IVF Embryo Development Day by Day 0-5 Days
Now, we will understand embryo development day by day.
Day 0: The Pronuclear Stage
Fertilization of an ovum by a sperm does not take place instantly. The two gradually fuse for 4–6 hours. The primary sign of fertilization is the existence of two circular figures called the female pronucleus and the male pronucleus. Each part contains a set of 23 chromosomes, representing an equal genetic piece from each parent. The two cells fuse in a phenomenon known as syngamy, creating a cell with 46 chromosomes.
Although the embryo would still move through the dividing stages and implant itself in the uterus, it wouldn’t result in a viable pregnancy. Now, the fertilized eggs are checked to ensure everything is acceptable or not. If there are any abnormalities, it’s essential to debug them before the cell division process.
Once the pronuclei join, fertilization is fully completed, and a zygote is formed. The entire mechanism — from the moment the sperm and egg connect to the moment cell division begins — takes approximately 30 hours.
The fertilized egg will divide every 10-12 hours into a two-celled, four-celled, 8-celled embryo. After the 16-32 cell division stage, the cells become compact and coalesce together into a moral.
Days 3-5: The Morula Stage
As soon as the cleavage stage ends, the morula stage starts. The morula stage composes the zygote (currently 16 cells, still undergoing division) to grow further. The cells position themselves into a hollow circle to simplify transitioning into the blastocyst stage.
Day 5: The Blastocyst Stage
It is contemplated as the final stage of zygote development—the arrangement defined above permits the growth of two layers of cells. The outer ring offers the tissues required for a successful pregnancy, comprising the placenta and amniotic sac. Inside this protective outer ring, a group of cells will substantially develop into a healthy newborn.
The zygote hatches and attaches to the mother’s uterine wall. And this is when the zygote develops into an embryo. The zygote will begin to expand, breaking its protective shell and preparing itself for implantation as soon as the surface bursts.
Understanding Embryo Grading
Embryo grading is a method IVF experts use to enhance your chances of conception. The specialists will grade your embryos with proper care in the IVF lab, selecting the ones with the best capability for plausible implantation. Additionally, they also take notes of embryo development day by day. Grading takes place on day three and day 5, according to different sets of criteria. Implantation is usually done on either day three or day 5.
Initially, each fertilized egg is observed to identify the best zygote. Zygotes are evaluated in two ways. The first examines the contact point between nuclear membranes, while the second concerns the cell composition of the zygote.
On the 3rd day of screening, the embryos are observed by experts under a microscope. Additionally, the amount of cytoplasm in each cell is also measured. The ones with a more significant number of genetic material cells and a good cytoplasm ratio to nuclei obtain a higher grade. Furthermore, cell symmetry is evaluated — more symmetrical cells, more advantages.
When the screening begins on the 5th day, the cells grow, and the zygote is nearly ready to burst out of its shell. A letter grade must be allocated to both the outer ring of cells and the group of cells inside the circle. Both are required for a viable pregnancy.
Additionally, grading also contemplates your age once you are trying to conceive, fertility history, and the section of your cycle when selecting the best moment for implantation. Will the most credible transfer the perfect number of embryos on the 5th day.
Why is chromosome screening important?
It is a personal decision to perform chromosome screening before the IVF Treatment. It can only be achieved when the embryo is outside your body, throughout the 5-day duration between fertilization and implantation.
PGS is done to screen and discard chromosomally abnormal embryos that develop randomly during the above process of egg and embryo development in all couples, 99.9% of whom would have themselves a regular genetic makeup. Women aged above 35, prior history of failed IVF, previous miscarriages, and plan to transfer a single embryo to limit twins are some typical indications for PGS/ PGT A.
When is IVF needed?
The IVF embryo development process should be used when the chances of pregnancy with IUI are low but comparatively higher with IVF. It is the ideal solution when infertility is due to blocked fallopian tubes or male infertility.
Are there risks with having an IVF baby?
Multiple births are an issue regarding IVF embryo development. This process enhances the risk of multiple births if more than one embryo is transplanted to your uterus.
Are IVF babies healthy?
The answer is YES. Thousands of children have taken birth using this IVF embryo development process. It does not pose any short-term or long-term threat to the child.
Is IVF using all eggs of women?
Synthetic hormones are used to mature multiple eggs. These eggs are needed as some eggs would not fertilize even after fertilization.