An embryo is formed in the early stage of development after fertilization or when the cells start to divide. These embryos can be preserved for future use through a procedure called embryo freezing. Apart from embryos, females can also freeze their unfertilized eggs. The first ever successful pregnancy from a healthy frozen embryo took place in the 1980s. After this many people came up with the idea of freezing up their embryos for later use. A person may decide to preserve an embryo for various reasons like for medical research, for training purposes, to donate to others, or if they desire to get pregnant in the future.
The process to freeze an embryo begins by stimulating the production of potentially fertile eggs by using various hormones and other kinds of medications. These fertile eggs are extracted from the ovaries either for fertilizing in the lab or for freezing. One healthy embryo can be produced after a successful fertilization and then this embryo is either transferred to the uterus or womb where the embryo will develop.
What is an embryo and how do people create one?
The medical community uses the term embryo from the moment when cells divide after fertilization until the eighth week of pregnancy. Before freezing, doctors and laboratories must harvest and fertilize some eggs.
In the beginning, people are administered hormones to make sure that ovulation occurs on schedule. They will take some additional medications to increase the number of eggs that they produce.
Doctors may use various techniques like in-vitro fertilization (IVF) or intracytoplasmic sperm injection (ICSI) for the person who wishes to freeze their eggs or wishes to use them at once to become pregnant.
During IVF eggs are exposed to sperms and are left in the laboratory for fertilization. For a period of six days, an embryologist will monitor the development of the embryo after which a suitable embryo is selected for implantation.
During ICSI a single sperm is directly injected into the egg. This technique is used when there is a problem with the sperm or if previous attempts at IVF have not resulted in fertilization.
How do people freeze embryos?
The main problem with freezing the embryo is the water inside the cell. During the process, this water freezes, and crystals can form which may burst the cell.
To prevent the cell from bursting, doctors replace the water in the cell with a substance called a cryoprotectant through the process popularly known as cryopreservation. Before freezing, the embryos are left to incubate in the increasing level of the cryoprotectant. After removing the maximum amount of water from the cell, the embryos are cooled down to their preservation state.
The two freezing methods generally used by doctors are:
- Slow freezing: In this process, the embryos are placed in sealed tubes and then the temperature is slowly lowered. This process inhibits the embryos cell from aging and also reduces the chances of it getting damaged.
- Vitrification: In this process, the cryoprotected embryos are frozen so quickly that the water molecules are not able to form crystals.
After the completion of the freezing process the embryos are stored in liquid nitrogen.
Success rate of thawing frozen embryos:
Various research has proven that women who use thawed embryos have a good chance of delivering healthy babies. It also shows that the process of thawing an embryo after cryopreservation has a moderately high success rate. As per recent studies, babies born after cryopreservation showed no increase in developmental abnormalities. Some studies also suggest that vitrification increases the chances of the survival of the embryo both during freezing and thawing.
Side effects of freezing an embryo:
Various mild to moderate side effects which usually occur when the doctor is extracting the eggs are:
- Bloating or cramping
- Feeling full
- Changes in vaginal discharge
- Overstimulation of the ovaries
How long can embryos stay frozen?
The embryos are generally kept at -321 degree Fahrenheit temperature in a sealed container making them viable for any length of time. At this temperature, no biological process like aging can occur. There are many examples of successful pregnancies resulting from eggs that have been stored for up to 10 years.
Frozen or fresh embryos:
According to a study published in the International Journal of Reproductive Biomedicine, the researchers found no statistical difference between the fresh or frozen embryos in terms of pregnancy rate or fetal health. Many other studies favored the transfer of frozen embryos more than fresh ones.
Who can benefit?
Embryo freezing can be a better option for people such as:
- Person with a genetic disorder that affects fertility
- Person undergoing chemotherapy
- People who are on medications that affect reproduction
- LGBTQ+ people who wish to have children
Freeze all cycle:
A doctor uses freeze all cycles to extract an embryo, freeze and preserve it. People with ovarian stimulation syndrome may benefit from this process as this condition arises when a person is receiving stimulating hormones to increase egg production. A freeze all cycle can be used to test an embryo for a genetic disorder by removing a few strands of DNA and testing the chromosomes.
Embryo freezing is one of the best and safest options that often lead to successful pregnancy and delivery. There is some possible risk which includes chances of genetic abnormalities in the child, or women who become pregnant at a later age may have the chances of some complications. Sometimes fertility treatment can also lead to ovarian hyperstimulation syndrome.
This treatment is very expensive but it also offers a wide range of options for people who wish to delay pregnancy or who may otherwise be unable to conceive.
Dr. Gauri Agarwal is one of the best-known Infertility and IVF Specialists in India with over 15 years of experience in the field of gynecology and infertility. She is also the Founder-Director of Seeds of Innocence, a reputed and recognized chain of IVF Centers and Gene strings Diagnostic Centres.