PGS/PGT-A, preimplantation chromosome examination, or preimplantation chromosome aneuploidy examination, also known as the third generation test-tube baby. ? This technique is to improve the pregnancy rate or reduce the probability of abortion after implantation by checking whether the embryo chromosome is normal before implantation, so as to achieve the purpose of early pregnancy. ?
This article will explain to you the advantages, limitations and precautions of PGS/PGT-A?
Chromosome examination before PGS embryo implantation
Chromosome examination before embryo implantation;
PGS: preimplantation Geic screening, now also known as PGT-A: preimplantation Geic (gene) detection of aneuploidy. With the help of modern biotechnology, it is necessary to check whether the chromosome of the embryo is normal before implantation, so as to reduce the chance of abortion of IVF and improve the pregnancy rate of IVF after implantation. ?
Who needs PGS?
It is suggested that couples with advanced age, repeated test tube failures and chromosomal abnormalities receive PGS.
An advanced/venerable age
As women get older, the quality of eggs will begin to decline. If you are over 34 years old, you are considered old, and the success rate of test tubes over 38 years old begins to decline rapidly. If you are over 40, it will be even more difficult. ?
According to statistics, the probability of chromosome abnormality in female eggs is positively correlated with age. Only one out of every 20 eggs in a 20-year-old woman has normal chromosomes, while one out of every 30 eggs in a 30-year-old woman has normal chromosomes, while a 40-year-old woman needs normal chromosomes in 40 eggs. ?
Therefore, when the elderly women receive IVF treatment, PGS should give priority to the elimination of embryos with abnormal chromosomes, so as to reduce the abortion rate after embryo implantation and improve the chances of successful implantation of a single embryo. ?
Repeated pipeline failure
Generally speaking, the pregnancy rate of a test tube is about 50% ~ 60%, so if you accept three times of in-vitro embryo implantation, the pregnancy rate should be 80% ~ 90%. If the embryo is implanted three times, it will not succeed. In addition to further examination, we should also consider whether the proportion of abnormal embryos is high, so PGS should find out normal embryos and improve the chances of embryo implantation. ?
chromosome
Generally, normal cells have 23 pairs (46 * * *) of chromosomes, 46XY for boys and 46XX for girls. ?
In the process of making eggs and * * * *, chromosomes undergo meiosis (that is, from 46 to 23). After each egg with 23 chromosomes is fertilized with * * *, an embryo with 46 chromosomes will be formed, and finally a normal baby will be implanted, developed and produced. ?
However, in the process of sperm egg production, chromosome division will make mistakes, thus forming chromosome abnormalities and * * *. This abnormal combination of sperm and eggs will develop into abnormal embryos. Most abnormal embryos will be naturally eliminated (that is, they will not be implanted) or spontaneously aborted (they will not develop after implantation). A few abnormal embryos will survive and give birth to babies with abnormal chromosomes. The most common is Down syndrome. ?
However, there are also a few couples, because of their own chromosomal abnormalities (it may be a small chromosome deletion, a chromosome inversion, or a chromosome mosaic, but it does not affect their own growth and development). However, in the process of sperm egg production, it cannot be repaired by itself, so the proportion of sperm egg production is very high, and the embryo formed after sperm egg combination is also abnormal. Such embryos can't develop normally, and almost 100% will miscarry. ?
Therefore, PGS can know these abnormal embryos in advance, thus reducing the probability of abortion after embryo implantation. ?
Results of traditional in vitro fertilization
The result of traditional IVF is the same as that of natural pregnancy. In fact, the quality of ovulated eggs by injection is similar to that of husband's sperm collection. According to statistics, among the embryos implanted by traditional IVF, even the 5th day 5AA blastocyst with the best appearance quality, the abortion rate after implantation is 15% ~ 20%. ?
As mentioned earlier, the reason of abortion is that there is a problem in the production process of * * * and eggs. Therefore, although the appearance looks the best, the chromosome inside the embryo is abnormal, and the probability of abnormal abortion of the embryo is greatly improved. (Of course, the better the embryo appearance, the higher the proportion of normal chromosomes. The worse the embryo appearance, the lower the proportion of normal chromosomes. )?
Therefore, we found that the higher the age, the lower the embryo implantation rate and the higher the probability of miscarriage. ?
PGS can reduce the chance of miscarriage.
However, with the development of biotechnology and the invention of NGS (Next Generation Chromosome Analysis Technology), with the help of embryo sectioning and embryo chromosome examination, we can reduce the probability of abortion after embryo implantation and improve the pregnancy rate and the live birth rate of each implantation. ?
Traditional test-tube vs. the third generation test-tube baby
Let's compare the differences between "traditional test tube" and "chromosome examination before PGS embryo implantation (third generation test tube baby)" in detail. ?
In traditional test tubes, the pregnancy rate of two embryos implanted in a single cycle (good blastocysts on the fifth day) is about 50% ~ 60%, and the abortion rate after embryo implantation is about 15%. The fee is the general test-tube baby fee, and the time from egg retrieval to pregnancy test is about one month. ?
In the third generation of IVF, the pregnancy rate of one embryo implanted in the embryo implantation cycle is 50%, and the pregnancy rate after embryo implantation is less than 5%. Overall costs (including injection, egg retrieval, embryo culture, slicing, chromosome examination, embryo thawing and implantation, etc.). ) You can do a traditional test-tube baby about three times, and it takes at least three months. ?
It can be seen that the third generation test tube has the advantages of high pregnancy rate and low abortion rate compared with the traditional test tube, but it has high cost, long time and more restrictions. ?
Review again: check PGS before embryo implantation. When embryos with normal chromosomes are implanted, the pregnancy rate of a single embryo is 50% and the abortion rate is less than 5%. ? The footsteps of PGS
As mentioned above, the pregnancy test from PGS to embryo implantation takes three months. Let's take a look at the steps of PGS. ?
The simple steps of PGS can be divided into three parts, and each step can also be divided into three details. Now let's take a closer look. ?
PGS trilogy
Step 1. Inject, take eggs and raise embryos.
Step 2: Embryo section and chromosome examination.
Step 3: Establish intima and unfreeze embryo implantation.
Step 1.
Injection, egg collection and embryo culture
This stage is to cultivate embryos, which is the same as the steps before implantation of traditional IVF embryos. ?
Step 1. 1: MC started injection and ovulation the next day.
Like the traditional test tube, MC begins to ovulate on the second or third day after seeing red, and at this time, the egg is matured by injecting an egg-breaking needle. You can all take the next step. ?
Step 1.2: Ovulation under general anesthesia.
Same as the traditional test tube, it received intravenous general anesthesia, no intubation and egg retrieval operation. It takes about 30 minutes to take eggs, 30 minutes to prepare ahead, and anesthesia recovery after operation 1 hour. After taking the egg, the egg will be handed over to the embryo technician, and the subsequent embryo culture process will begin. ?
Step 1.3: Sperm-egg combination and embryo culture.
In the process of PGS, the way of sperm-egg combination (that is, egg fertilization) is ICSI (single sperm microinjection), rather than the traditional natural fertilization of sperm and eggs. Using ICSI can avoid the influence of extra chromosomes on the correctness of subsequent chromosome examination. The fertilized egg begins to enter embryo culture. ?
Step two. ?
Embryo section, chromosome examination?
This step is the most complicated part of PGS. After a series of treatments, embryos raised to the fifth and sixth days can be examined. ?
Step 2. 1: Embryo culture until the fifth and sixth day.
In the past, most embryos of PGS were taken out from the third day for embryo sectioning. However, in recent years, international literature has found that the results of blastocyst sections on the fifth and sixth days are more accurate. Therefore, in recent years, the international standard of PGS suggests that blastocysts (blastocysts on the 5th and 6th days) should be sliced on the 5th and 6th days. ?
After selecting embryos, laser thinning and artificial incubation (AH) are needed. Laser thinning is to make a small hole in the embryo's shell with an accurate laser, so that some embryonic cells protrude from the embryo's shell, which is convenient for everyone to come down and make embryo slices. ?
Step 2.2: Embryo slicing
On the fifth day of embryo culture, after some embryo cells bulge out of the shell, the embryologist will use embryo slicing technology to pick up five or six outer ring cells (trophoblast cells), also called trophoblast biopsy. The selected cells will be put into a special chromosome analysis tube for PGS to prepare for chromosome analysis. ?
Step 2.3: Chromosome examination and embryo freezing.
Cell samples were analyzed by NGS. NGS is the next generation chromosome analysis, which uses the same fragment in the human chromosome gene bank to analyze whether the embryo chromosome is normal or not through computer analysis and calculation. NGS is a new method, which is more accurate and more expensive than traditional FISH, but it is also a standard method for international inspection. ?
Therefore, it is more correct to combine PGS with NGS. ?
The sliced embryos will be vitrified in a liquid nitrogen barrel at-198 degrees, waiting for the results of chromosome examination. The thawing survival rate of vitrified embryos is above 99.9%, which is the only standard for freezing embryos now. Embryos are kept in liquid nitrogen barrels and the environment is stable. It can be stored for ten years without any problems. ?
Step three. ?
Establish intima, thaw embryo implantation.
After the chromosome analysis is completed, if there are embryos with normal chromosomes, the third step can be started: unfreezing non-fetal implantation. This step is similar to the traditional IVF cycle. ?
Step 3. 1 step: MC began to take oral drugs to establish intima the next day.
Taking estrogen, simulating normal physiological hormones, the intima gradually thickens. (If lutein is banned in this period, it will be a failure, a failure. Don't believe the rumors on the Internet: lutein can help the embryo implantation, so use lutein early. The use of lutein in this period will only make the endometrium unable to implant embryos because of premature luteinization. )?
Step 3.2: Good luck.
It's time to start using lutein. Generally, estrogen is used to make the intima grow to more than 0.8 cm, so you can calculate the time and start using lutein.
Step 3.3: Thaw the embryo for implantation.
After using lutein for five days, you can prepare to thaw the embryo for implantation. After two weeks of embryo implantation, you can have a pregnancy test. ?
Normal embryo
Again, share your clinical experience briefly. How many normal embryos are there in a PGS cycle? If the age is less than 38 years old, if there are 12 eggs in an egg retrieval cycle, there will be about 10 fertilized eggs after fertilization. On the fifth day, there will be about 3-5 blastocysts that can be sliced, and there will be about 2-3 normal embryos after slicing. ?
However, if couples with chromosomal abnormalities are over 38 years old or have fewer eggs than 12, there may not be so many embryos with normal chromosomes. ?
Therefore, couples planning to go to PGS need to receive one-on-one professional consultation before the course of treatment, so as to accurately analyze and evaluate. ?
conclusion
PGS combined with NGS can improve the pregnancy rate after single embryo implantation and reduce the probability of abortion after embryo implantation. If you are old, have the experience of repeated test-tube failures, or have problems with abnormal chromosomes of husband and wife, it is recommended to use PGS to improve the chances of test-tube success. ?