Latest research: Chimeric embryos can also successfully give birth to test-tube babies

One limiting factor for the success of in vitro fertilization (IVF) is the number of viable embryos that can be implanted in the uterus
.
On November 19, a study published in the American Journal of Human Genetics showed that many embryos discarded or downgraded due to chromosomal abnormalities may lead to a successful pregnancy
.
These findings may have important implications for people undergoing IVF
.

"We believe that these clinical data will solve some of the major problems in preimplantation genetic testing, and further help many infertile patients make more informed fertility decisions
.
" Scientific expert Antonio Capalbo said, “This trial may promote changes in IVF clinical management and support relevant departments to update guidelines and recommendations
.
”

Researchers studied the prevalence and distribution of aneuploid cells (cells with unbalanced chromosomes) in blastocysts (embryo precursors) made in the laboratory
.
They particularly observed a condition called chimerism, where both normal and aneuploid cells are present in the embryo
.
Currently, less than 3% of chimeric embryos are used for IVF, and some clinics in the United States do not allow them to be transplanted
.
But the researchers found that in many of these chimeric blastocysts, the abnormal cells are confined to a small area that may not affect development
.

This time, the researchers conducted a double-blind trial.
They selected patients who received IVF from 5 hospitals in Italy.
Before implantation, the researchers conducted genetic tests on the embryos
.
In addition to euploid embryos, implanted embryos also include low chimerism (20% to 30% aneuploid cells) and medium chimerism (30% to 50% aneuploid cells)
.
The researchers said that the main result of the experiment was the live birth rate, and the secondary result was the abortion rate
.

"It is known that chimeric embryos may develop to term and produce healthy babies
.
However, many previous studies have been affected by selection biases, which tend to have a poor prognosis.
These patients have previously used euploid embryos.
The transfer failed
.
" He said, "In addition, the chimeric embryos were transferred to patients who only produced aneuploid embryos, again introducing a strong selection bias to people with poor prognosis
.
"

The researchers say that the current study avoids this prejudice through non-selective trials
.
In this test, any embryo that meets the criteria is eligible for transplantation
.
In total, they found that in 484 euploid, 282 low chimera and 131 medium chimera embryos, the live birth rate and abortion rate were similar
.
Obstetrics and newborns have similar results
.

Capalbo said, “Our results show that the current mosaicism research does not provide any clinically useful information for IVF recipients
.
Therefore, it seems reasonable not to report relevant results after pre-implantation genetic testing.
The treatment of variants of unknown significance in clinical genetic testing is similar
.
Even if these findings are reported, patients should be aware that the embryos are otherwise healthy and normal
.
"

The researchers hope that this study will immediately affect clinical practice, prompt relevant departments to update guidelines and recommendations, and allow patients undergoing IVF to improve the decision-making process when evaluating chimeric embryo transfer
.
(Source: Feng Lifei, China Science News)

Related paper information: https://doi.
org/10.
1016/j.
ajhg.
2021.
11.
002