Last Updated on 10 November 2024 by HealthSmile medical writer team
After ICSI and embryo chromosome testing, do I need to do NIPT or NIFTY testing again?
Congratulations to the pregnant mothers, whether they get pregnant naturally or use technology such as in vitro fertilization (IVF), ICSI (Intracytoplasmic sperm injection) or other methods of using technology to help with pregnancy. The embryos can be screened for chromosomes before implantation, or PGT-A, which will allow selecting only embryos with a normal number of chromosomes to be implanted into the uterus of the pregnant mother. In the case of the mother, after checking the embryo chromosomes, is it necessary to screen for Down syndrome during pregnancy (NIPT or NIFTY)? This article will provide the answer.
Should IVF babies who have had their embryos chromosomal tested before being placed in the uterus still undergo NIPT or NIFTY?
[IVF] After ICSI and chromosome testing before embryo transfer, do I need to do NIPT or NIFTY testing again? The answer is that you can choose whether to do it again or not. However, if you are worried, it is recommended that you do it again. It depends on the family’s wishes whether they want to do it or not.
Reasons for recommending repeat chromosomal screening
Chromosome deficiency is the most common abnormality in embryos obtained from IVF. We generally know that the main risk factor for chromosomal deficiency is the maternal age. There have been clear studies that selecting embryos with normal chromosomes by PGT-A (Preimplantation Genetic Testing for Aneuploidy) or formerly known as PGS (Pre-implantation genetic screening) can reduce the chance of pregnancy with a baby with chromosomal abnormalities. In addition, it also increases the chance of increasing the percentage of setting. PGT-A has an accuracy of approximately more than 95%, which is considered highly accurate in detecting abnormalities caused by chromosomal deficiency. Therefore, if you can accept the small chance of error, there is no need to repeat the NIPT test.
What does the accuracy of preimplantation genomic testing (PGT-A) depend on?
- Quality of cells sent for testing: If the cells obtained are of low quality or have been stored for a long time before being sent to the testing machine, the results will be inaccurate.
- Techniques used for testing: There are several techniques used for testing PGT-A, such as in the past, fluorescence in situ hybridization (FISH), comparative genomic hybridization (CGH), and currently, next-generation sequencing (NGS) is used, which is considered the most accurate method currently available.
- Expertise of the testing lab: Since the results are from a small number of cells, the person conducting the test must be an expert, and the testing equipment must be accurate.
- Stage of embryo examined: The examination at the blastocyst stage is currently considered to be more accurate than the examination at earlier stages.
- Embryonic Mosaicism: Embryonic Mosaicism is a condition in which the embryo contains both normal chromosomal cells and abnormal chromosomal cells. If only normal cells are selected for testing, the PGT-A test may produce inaccurate results.
- Chromosomal or genetic abnormalities of the parents: Some abnormalities cannot be detected by the PGT-A test.
It can be seen that the PGT-A test has many limitations. There may be errors in interpreting the results because the amount of DNA collected from the embryo cells is too small. In addition, there may be a mosaic condition, which is when the chromosomes of each child’s cell are different. Therefore, even if the cells tested have normal results, it may not be possible to tell that all the other cells are normal.
Screening for chromosomal abnormalities after successful pregnancy
Currently, if the mother is able to get pregnant, there are several genetic screening methods during early pregnancy, such as ultrasound examination to check the thickness of the baby’s neck, maternal blood chemical test (PAPP-A), NIPT test, etc. (Read more How many types of blood tests are there for Down syndrome screening? ) นอกจากนี้ยังมีการตรวจวินิจฉัยได้แก่ การเจาะน้ำคร่ำ หรือการตัดชิ้นเนื้อรกบางส่วนมาตรวจหาความผิดปกติของโครโมโซมได้เช่นเดียวกัน แต่ทั้งวิธีเจาะน้ำคร่ำ หรือการตัดชื้นเนื้อรกนี้ ก็เพิ่มความเสี่ยงที่จะทำให้เกิดการแท้งบุตรได้ ซึ่งการตรวจเมื่อตั้งครรภ์แล้วนั้น ก็จะมีประโยชน์เพราะว่าเป็นการตรวจคัดกรองโครโมโซมในทารกที่ยืนยันการมีชีวิตแล้ว และช่วยเพิ่มความมั่นใจให้กับคุณแม่และครอบครัวได้เป็นอย่างดี นอกจากนี้ การตรวจ NIPT หรือ NIFTY นั้น ยังสามารถตรวจภาวะที่มีการขาด/เกินของโครโมโซมขนาดเล็กๆ (deletion/duplication syndrome) ซึ่ง PGT-A ไม่สามารถตรวจได้ (อ่านต่อ : NIFTY®️ Pro เพิ่มรายการตรวจ deletion/duplication จาก 84 เป็น 92 รายการแล้ว)
summarize
It can be seen that even though mothers who undergo IVF have undergone chromosomal screening before placing the embryo into the uterus, there is still a chance that the embryo will have chromosomal abnormalities due to 2 reasons:
- Mosaicism is caused by the cells of each embryo having different chromosomes. Therefore, if only some cells of the embryo are randomly selected for examination, there is a chance that only normal cells will be obtained, but no cells with abnormal chromosomes will be obtained.
- Taking only a few cells from the embryo (which has a small number of cells to be tested) may cause a limitation in the amount of DNA to be tested, which is too little.
In addition, the limitation of PGT-A is that it cannot detect abnormalities caused by the lack/excess of small chromosomes (deletion/duplication syndrome) . Therefore, to be sure that the baby in the womb has normal chromosomes, doctors recommend that mothers can choose to screen for additional chromosomal abnormalities (such as NIPT, NIFTY) or choose to diagnose by amniocentesis or placental biopsy. However, chromosomes are like the mold of life. Mothers still need to receive nutrition, love and warmth throughout pregnancy. They also need to receive quality prenatal care and care according to the specified criteria. Even if all test results are normal, all mothers will have a basic risk of 3 to 5% for any pregnancy that will result in the baby having a congenital disability or mental retardation. Prenatal screening and diagnostic tests cannot detect all abnormalities. Normal test results do not guarantee that they will be normal until the time of delivery.
References
Kimelman, D., Confino, R., Confino, E., Shulman, L.P., Zhang, J.X., & Pavone, M.E. (2018). Do patients who achieve pregnancy using IVF-PGS do the recommended genetic diagnostic testing in pregnancy? Journal of Assisted Reproduction and Genetics, 35(10), 1881–1885. https://doi.org/10.1007/s10815-018-1289-z
Kimelman, D., & Pavone, M.E. (2021). Non-invasive prenatal testing in the context of IVF and PGT-A. Best Practice & Research. Clinical Obstetrics & Gynecology, 70, 51–62. https://doi.org/10.1016/j.bpobgyn.2020.07.004
Madjunkov, M., Abramov, R., Glass, KB, Baratz, AY, Sharma, P.A., Madjunkova, S., & Librach, C.L. (2023). Noninvasive prenatal testing (nipt) after euploid embryo transfer shows high concordance with pgt-a results and low nipt predictive values. Fertility and Sterility, 120(4), e50. https://doi.org/10.1016/j.fertnstert.2023.08.165