胚胎著床前基因診斷對人工生殖技術之探討

Abstract

研究背景：高齡女性在進行人工生殖技術時容易會有非整倍體（Aneuploid）染色體的胚胎，是造成IVF失敗與流產的主要原因。帶有特定遺傳疾病家族史的夫婦，必須避免遺傳疾病在下一代的子女身上也發生。胚胎著床前基因篩選（PGS）和胚胎著床前基因診斷（PGD），是近年來新興替代性的產前基因檢測技術，也就是利用人工生殖的技術（IVF）的平台，在胚胎培養至第三天或第五天時，先進行胚胎細胞的切片，再經由分子醫學的技術進行染色體的篩檢或基因檢測，以篩選出正常的胚胎再植入母體子宮內生長發育成為胎兒。 研究目的：乃探討高齡、反覆不明原因流產或家族中帶有特定遺傳性疾病之婦女，在經由PGS、PGD之人工生殖技術後是否能夠提高懷孕率並降低流產率，並探討其後續懷孕婦女之胎兒產前基因診斷之方式。 研究對象與方法：本研究收集的臨床個案經由人工生殖評估與遺傳諮詢後，以Array-CGH或Linkage analysis進行胚胎著床前基因檢測，篩選正常的胚胎植入。另有一般傳統IVF的新鮮胚胎植入療程作為對照組。將所有患者的數據資料進行分析與比較。 研究結果：37 例PGS個案中共執行42 個cycle的IVF療程，共有7例個案無正常胚胎可以植入，在26個植入週期中有15例個案懷孕，懷孕率為57.7％(15/26)，3位孕婦流產，流產率為20％(3/15)，迄今為止共有3位健康寶寶出生。5例攜帶染色體平衡性轉位個案中共執行7 個cycle的IVF療程，有1例個案無正常胚胎可以植入，在4個植入週期中有2例個案懷孕，懷孕率為50％(2/4)，並無孕婦流產，流產率為0％，迄今為止已有1位健康寶寶出生。22例PGD個案中共執行33個cycle的IVF療程，有2例個案無正常胚胎可以植入，在19個植入週期中有11例個案懷孕，懷孕率為57.9％(11/19)，7孕婦流產，流產率為63.6％(7/11)，迄今為止已有1位健康寶寶出生。在孕婦進行胎兒產前基因診斷部分，不論是NIPT、羊水染色體核型分析或羊水晶片都有個案進行。 結論：臨床研究結果顯示進行PGS和PGD檢測後，確實能提高執行IVF之懷孕率（分別是57.7％和57.9％）。然而在流產率部分則顯示PGD(63.6％)>IVF(35.3％)>PGS(20％)，這顯示在進行特定遺傳疾病檢測後，如果沒有再進行PGS之染色體篩檢，則可能會有流產的機會。另一方面根據胎兒產前基因檢測結果與出生寶寶的健康情況可以證實胚胎著床前基因檢測是一項既安全又可靠的技術。

Background: The dramatic decline in IVF success rate of patients with advanced maternal age is primarily caused by aneuploidy. Chromosomal aneuploidy is also attributed to implantation failure and abortion. Pre-implantation genetic screening (PGS) is currently the technique to avoid this. Couple with genetic diseases now can prevent an affected offspring by pre-implantation genetic diagnosis (PGD). PGS and PGD are increasingly applied in IVF field recently to decrease the future dilemma of abortion. They are multistep procedures requiring expertise both in reproductive medicine and genetics. Embryo biopsy is performed on cleavage stage embryos (day 3) or blastocysts (day 5) and biopsied material is submitted for genetic analysis. Embryos with chromosomal euploidy or genetic unaffected pattern will be selected and transferred back to uterus to improve success rate. Objectives: The aim is to determine whether PGD or PGS has the potential to increase pregnancy rates in patients undergoing IVF program. Subjects and Methods: This descriptive study included PGS, PGD and IVF data. Array CGH is used for PGS and molecular technologies such as direct sequencing and linkage analysis are used in PGD. The data are analyzed. Results: 37 patients who underwent 42 cycles of PGS. No euploid embryo was available in 7 patients. 15 patients out of 26 transfer cycles got pregnant with a pregnancy rate of 57.7% per transfer. Three women had miscarriage with abortion rate of 20% (3/15). Three patients delivered 3 healthy babies. There are 5 couples with balanced translocation. Five patients underwent 7 cycles of PGD and no euploid embryo was available in 1 patient. Two patients got pregnant in 4 transfer cycles with pregnancy rate per transfer cycle being 50% (2/4). No miscarriage occurred and abortion rate was 0 %. Till now, one baby has been born. 22 patients who underwent 33 cycles of PGD and no normal embryo was available in 2 patients. 11 patients got pregnant in 19 transfer cycles with pregnancy rate per cycle being 57.9% (11/19). Seven women had miscarriage and abortion rate was 63.6% (7/11). Till now, one baby has been born. Conclusion: Application of PGD can improve the success rate for in vitro Fertilization. However, patients underwent IVF and PGD had higher abortion rate of 63.6% than that (20%) of patients with IVF and PGS. The data meant that PGS is necessary and important for patients undergoing PGD. Additionally, PGS and PGD is becoming a safe and highly accurate procedure.