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To make choosing embryo easier - Pre-implantation genetic screening (PGS in Taiwan)

How many embryos do you want to transfer? Which embryo do you want to transfer? Many IVF couples just looked down at the records of the frozen embryos with their puzzled faces, and finally decided to ask the technicians to help them to choose the best embryo for them.

To reduce the risk of multiple birth, such as gestational diabetes, ecplamsia, and premature birth, single embryo transfer (SET) has become more popular in the IVF realm. Specifically, the transferred embryo should be at the blastocyst stage because of its higher implantation rate and higher clinical pregnancy rate. Now the problem comes - how to choose the best blastocyst to be transferred?

According to the released report by Mackay Memorial Hospital in 2013 Annual Meeting of Taiwanese Society of Reproductive Medicine, they found the grading of embryo morphology and the maternal age were two crucial factors to the clinical outcomes through the retrospective study generated by 273 IVF cases recruited from 2009 to 2013. The data has been shown as follows,

Implantation failure
Number of IVF cases (%)
78 (28.6)
85 (31.3)
110 (40.3)
Grading of embryo morphology (Gardner Criteria)
 Young  ---------------------------- > Old
   Good   ---------------------------- > Poor
Number of retrieved eggsConcentration of oestrodial /progestosteroneAMHThickness of endometriumTiming of the triggered shot
No significant difference

They scored each embryo as following table, and then they transferred one single blastocyst when the total score was over 90. The rate of multiple birth was successfully reduced to 14.3% from 30% by this way.
6AA, 5AA, 4AA
4AB, 4BA, 4BB
3AA, 3AB, 3BA, 3BB
4AC, 4BC, 4CB, 3BC, 3CB
4CC, 3CC

Based on this rule, the clinical outcome of single blastocyst transfer (SBT) was displayed,

Number of cases
Clinical pregnancy(%)
Blighted ovum(%)
1st FET
14 (70.0%)
3 (21.4%)
2nd FET
3  (75.0%)
0 (0%)
Cumulative Pregnancy Rate

FET: Frozen-thawed embryo transfer

In the report released by Stork Fertility Center, we related the effect of the grading of embryo morphology and the maternal age with the chromosomal aneuploidy by the aCGH platform.
(Since 2015, we have shifted our PGS platform from aCGH to NGS, which is more robust in the detection of chromosomal mosaicism and segmental aneuploidy).

1. Trophectoderm cell grading: The chromosomal aneuploid rate was significantly higher in grade C embryo than that of grade A or B.

2. The formation rate of blastocyst: The chromosomal aneuploid rate was significantly higher in D6-formed blastocyst than that of D5-formed blastocyst in the group younger 35 years. In the group older than 35 years, the difference was not that obvious.

In conclusion, to evaluate the quality of a blastocyst, three factors were important grading of the embryo, maternal age and the formation rate of blastocyst. Nowadays, the PGS (aCGH) has become more ubiquitous before embryo transferring, and it improves the accuracy of choosing not only the "good-looking" one but also "chromosomal normal" one to be transferred.

Trophectoderm grade predicts outcomes of single-blastocyst transfers. Fertility and Sterility. 2013. 99(5): 1283-1289.

Stork Fertility Center Stork Fertility Center Author


  1. Recent years have seen great improvements of biotech techniques, which brought a lot of benefits to us.

  2. PGS is a comparatively new tech for us.

  3. Schedule your appointment with the Eva Hospital if anyone from you want the preimplantation genetic testing at affordable cost in India. We have the best team of the doctors that give you reliable treatment without any complications.

  4. Great Information about Embryo Transfer.Thanks for sharing this informative post.Your post has created some awareness in common people about Embryo Transfer. Read More information about fertility laparoscopic surgery chennai | non invasive surgery anna nagar

  5. Do you have any genetic disorders that you’re worried your child might inherit? Now, you can avoid making painful decisions, thanks to PGD testing. In Mumbai, IVF Spring is one of the leading clinics for PGD and PGS testing, in which the embryos collected during the IVF cycle are tested for various inherited disorders, and embryos that have the gene are not considered for implantation. This helps prevent genetic birth defects in children. PGD tests for a specific disease, which is great for parents who carry specific genetic disorders. PGS is more general, and tests for various disorders, which is normally recommended for mature couples, as well as women who face multiple miscarriages, to determine the cause. Our team of expert doctors work together to diagnose issues, as well as perform treatment procedures. Our success rates are among the highest in the market, along with a 96% satisfaction rate from our clients. We believe in personalized and customized care, where couples can freely come to us with queries or concerns, so that treatment is easy and stress free. Choose IVF Spring for your PGD and PGS testing, and ensure that your child has the best possible quality of life.


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