PGS/PGD , genetic screening and diagnostic technology

Before the embryo is transferred into the uterus, use the genetic material of the physiological embryo for analysis, to check whether the embryo carries the gene with genetic defect, and pick out the healthy embryo for transfer, so that the new born baby can avoid some genetic diseases.

IVF technology has really achieved “pre-natal and post-natal care”. It is mainly applicable to male and female infertility and elderly pregnant women with genetic history or chromosome abnormalities.

（1）Preimplantation Genetic Screening（ PGS）

PGS is an early prenatal screening method that detects the chromosome number and structural abnormalities of early embryos before embryo transferred, and analyzes whether embryos have genetic material abnormalities by detecting the structure and number of 23 pairs of chromosomes at one time.

Then to select healthy embryos and transfer them into the uterus, improve the clinical pregnancy rate of patients and reduce multiple pregnancy. PGS can not only treat infertility, but also has important function in blocking the transmission of genetic diseases and reducing human genetic load.

①    PGS can select healthy embryos, improve the success rate of IVF and reduce the abortion rate.

Compared with the traditional embryo morphology that relies on microscope technology to select embryos with high morphological level for transfer, PGS can directly analyze the genetic material of embryos, accurately judge whether there are chromosome abnormalities in embryos, and select really healthy embryos. Clinical tests show that PGS can reduce the abortion rate of recurrent abortion population receiving assisted reproductive therapy from 33.5% to 6.9% (Hodes wertzb, 2012), and increase the clinical pregnancy rate from 45.8% to 70.9% (Yang, 2012).

According to the MartinD. latest research results show that PGS can significantly improve various indicators of IVF (morphology compared with many indicators after embryo transfer screened by PGS). PGS can significantly improve the indicators of the first and second generation “IVF “, can improve the pregnancy success rate of the first and second generation “IVF”, reduce the rate of abortion and improve the quality of pregnancy.

②    Avoid multiple pregnancy and reduce the fetal reduction

The average success rate of IVF in China is 30-40%. In order to improve the success rate of one-time embryo transfer, 2-3 embryos will be transferred at the same time, so there are often some multiple pregnancy. Multiple pregnancy are more risky than singletons, and this risk exists for both mothers and children. Authoritative investigation found that the cesarean section rate of twins was 78.45%, premature delivery is about 47.07%, and complications and complications accounted for 39.7%. Twins and mothers of multiple pregnancy are more likely to develop gestational syndrome such as diabetes and hypertension during pregnancy, and the probability of postpartum hemorrhage is high. Most premature children develop congenital lung disease, which will last a lifetime.

Therefore, in order to protect the safety of mother and child, fetal reduction is required for more than triplets in principle. Fetal reduction has a 10% chance of causing all embryos to abortion. The Fertility and ART medical experts from Gen5 in the US, have always suggested that if adopt IVF technology, it’s the best to accept one embryo transferred, twins are not recommended, because this method is not good for mother and child.

Although there are no mandatory regulations in the US, if a female is transferred with an embryo and delivery twins finally, the doctor’s transfer is usually regarded as an unsuccessful transfer. Using PGS technology to select healthy embryos and improve the success rate of IVF, it can avoid the harm and ethical conflict caused by blindly transfer multiple embryos to improve the success rate of pregnancy.

（2）Preimplantation Genetic Diagnosis（ PGD）

PGD refers to pre implantation gene diagnosis, which is mainly used to check whether embryos carry genes with genetic defects. It appears on the basis of IVF technology. After sperm and eggs combine in vitro to form fertilized eggs and develop into embryos, genetic testing should be carried out before they are transferred into the uterus, so the IVF can avoid some genetic diseases.

PGD technology is currently applicable to two major categories of genetic diseases:

① Genetic disease caused by single gene mutation: the patient may have suffered from the disease, or husband and wife are recessive gene carriers of the disease. For example: cystic fibrosis, spinal muscular atrophy, fragile chromosome syndrome, muscular dystrophy, breast cancer and ovarian cancer susceptible populations (associated with BRCA or BRCA2 carry), and the remaining hundreds of autosomal recessive, autosomal abnormalities, or X chromosome related diseases.

② Chromosome translocation: this problems may be happen in healthy people. Their 46 chromosome structures have changed, but they have no health problems, they have a higher risk of miscarriage and a greater risk of birth defects in their offspring when trying to conceive. For example: chromosome reciprocal translocation, Robertson chromosome translocation, chromosome inversion, chromosome polymorphism rearrangement.