吳劭穎 院長 / 愛群試管嬰兒中心

PGS成功的三大要素: (1)良好的細胞培養環境(2)成熟的細胞切片和冷凍技術(3) 準確的染色體檢驗方式。全世界第一個試管嬰兒誕生於 1978年，而在六年後首例冷凍胚胎解凍後活產案例也成功問世，這些年來在這些方面的技術已經十分成熟穩定，對試管嬰兒成功率的貢獻也有目共睹。而染色體檢查的方式的發展也是突飛猛進，從初期的螢光原位雜交反應 (FISH) 到晶片式全基因體定量分析 (Array CGH)、次世代定序 (NGS)等新技術，所以這些進步到底對試管嬰兒成功率有無助益就是目前大家最想知道的答案。 

今年二月份人類生殖 (Human Reproduction) 期刊有發表一篇系統性文獻回顧，它把過去十年間PGS和試管嬰兒懷孕率相關的三千多篇文獻篩選後選出19 篇品質優良的研究做進一步分析¹，主要目的是探討植入外觀型態正常的胚胎 (外觀組)和根據PGS結果植入染色體套數正常的胚胎(PGS組)的懷孕率比較，並針對不同年齡層的再去細分。結果發現，在年輕的族群中(平均年齡< 35歲)並在植入相同胚胎數目的前提之下，所有納入分析的研究都發現PGS組有較高懷孕率，而且差異在統計學上是有顯著性的^2,3。另有一研究則發現外觀組植入兩個胚胎和PGS組植入單一胚胎的懷孕率相比在統計學上並沒有明顯的差異⁴，在年長的族群(平均年齡>35歲)研究中也有類似的發現，大部分PGS 組的懷孕率都較高，而且平均所植入的胚胎數目也較少^5,6,7,8。這些研究結果告訴我們，若選擇品質好(染色體數目正常)的胚胎植入除了可以提高懷孕率之外，同時也可以減少所需植入胚胎的數目以降低多胞胎的發生機率及相關的產科風險。 

著名物理學家愛因斯坦曾說過一句話“上帝不擲骰子”，背後涵義是他認為世界不該是單純由機率所支配，凡有因必有果。醫師不是上帝，PGS 也非萬能，但透過PGS 也可讓醫師和病人更加了解胚胎染色體狀況，在面對療程失敗時也有完整把所有的因素都納入考量，而不是單純用“機率”來概以論述。

參考資料：

1. Lee E, Illingworth P, Wilton L, Chambers GM. The clinical effectiveness of preimplantation genetic diagnosis for aneuploidy in all 24 chromosomes (PGD-A): systematic review. Hum Reprod. 2015 Feb;30(2):473-83. doi: 10.1093/humrep/deu303. Epub 2014 Nov 28. PMID: 25432917.
2. Scott RT Jr, Upham KM, Forman EJ, Hong KH, Scott KL, Taylor D, Tao X, Treff NR. Blastocyst biopsy with comprehensive chromosome screening and fresh embryo transfer significantly increases in vitro fertilization implantation and delivery rates: a randomized controlled trial. Fertil Steril. 2013 Sep;100(3):697-703. doi: 10.1016/j.fertnstert.2013.04.035. Epub 2013 Jun 1. PMID: 23731996.
3. Yang Z, Liu J, Collins GS, Salem SA, Liu X, Lyle SS, Peck AC, Sills ES, Salem RD. Selection of single blastocysts for fresh transfer via standard morphology assessment alone and with array CGH for good prognosis IVF patients: results from a randomized pilot study. Mol Cytogenet. 2012 May 2;5(1):24. doi: 10.1186/1755-8166-5-24. PMID: 22551456; PMCID: PMC3403960.
4. Forman EJ, Hong KH, Ferry KM, Tao X, Taylor D, Levy B, Treff NR, Scott RT Jr. In vitro fertilization with single euploid blastocyst transfer: a randomized controlled trial. Fertil Steril. 2013 Jul;100(1):100-7.e1. doi: 10.1016/j.fertnstert.2013.02.056. Epub 2013 Mar 30. PMID: 23548942.
5. Fishel SC, Craig A, Lynch C, Dowell K, Ndukwe G, Jenneer L, Cater E, Brown A, Thornton S, Campbell A et al. Assessment of 19,803 paired chromosomes and clinical outcome from first 150 cycles using array CGH of the first polar body for embryo selection and transfer. J Fertiliz In vitro 2011;1– 8.
6. Keltz MD, Vega M, Sirota I, Lederman M, Moshier EL, Gonzales E, Stein D. Preimplantation genetic screening (PGS) with Comparative genomic hybridization (CGH) following day 3 single cell blastomere biopsy markedly improves IVF outcomes while lowering multiple pregnancies and miscarriages. J Assist Reprod Genet. 2013 Oct;30(10):1333-9. doi: 10.1007/s10815-013-0070-6. Epub 2013 Aug 16. PMID: 23949213; PMCID: PMC3824853.
7. Sher, G., Keskintepe, L., Keskintepe, M., Maassarani, G., Tortoriello, D., & Brody, S. (2009). Genetic analysis of human embryos by metaphase comparative genomic hybridization (mCGH) improves efficiency of IVF by increasing embryo implantation rate and reducing multiple pregnancies and spontaneous miscarriages. Fertility and Sterility, 92(6), 1886-1894. https://doi.org/10.1016/j.fertnstert.2008.11.029.
8. Forman EJ, Tao X, Ferry KM, Taylor D, Treff NR, Scott RT Jr. Single embryo transfer with comprehensive chromosome screening results in improved ongoing pregnancy rates and decreased miscarriage rates. Hum Reprod. 2012 Apr;27(4):1217-22. doi: 10.1093/humrep/des020. Epub 2012 Feb 16. PMID: 22343551; PMCID: PMC3303493.