| 摘要: | 應用羊膜腔穿刺術來進行偵測產前胎兒遺傳性疾病，染色體檢查是目前最常用的檢查方法之一，而染色體異常最常見的疾病是造成中度智障的唐氏症，舉凡現代醫學的進步及產前超音波不斷的研發出3D立體影像，但諸如唐氏症只能再懷孕中期二十週以後才慢慢顯現出特殊表徵，或由相當有超音波經驗的產科醫師在早期篩檢胎兒的頸部透明帶是否增厚而進一步抽取羊水進行染色體確認檢查。縱使抽取羊水染色體檢查可篩檢胎兒染色體異常的準確率高達百分之九十九，但畢竟羊膜腔穿刺術是一種侵入性的產前診斷方法，雖然其危險機率低於1%。
本研究為了探討那一個族群的適應症是染色體異常率最高亦即敏感性最高，我們統計分析自1995到2007年共十三年來，羊水檢體來源自中國醫藥大學附設醫院基因醫學部細胞遺傳實驗室共16315個個案，其中抽取羊水染色體適應症最大族群為高齡產婦佔59.91%，母血血清篩檢異常佔22.36%，超音波篩檢異常佔9.76%，有異常家族史的佔2.23%，其他原因佔5.64%。染色體平均總異常率為2.30%。而在染色體異常中，數目異常佔62.13%，包括體染色體異常、性染色體異常及鑲嵌型。其他為構造異常，包括缺失、移位、複製、倒位、插入等等平衡性或非平衡性構造異常。
我們的統計分析顯示，雖然高齡產婦為染色體適應症最大族群，但此族群卻不是染色體異常率最高亦即敏感性最高的族群(1/49)，而是-產前超音波篩檢異常的敏感性最高(1/22)。但若只針對異常的唐氏症(三染色體21症)去做最大族群的統計，高齡產婦即是唐氏症最大的族群(57/110)。綜合以上數據我們下了一個結論，亦即高齡產婦若同時有產前超音波篩檢異常或同時出現母血唐氏篩檢異常，我們即有足夠的理由進行下一步產前羊膜腔穿刺術，如此能提高產前異常偵測率及減少不必要的羊水抽取。同時我們研究統計的資料分析，希望能提供高危險群懷孕婦女些許關於染色體異常及正確的遺傳諮詢，而進一步減少產下染色體異常的胎兒。
Amniocentesis has been applied in prenatal genetic diagnosis. The number of women undergoing amniocentesis increased during these years. Among all the prenatal detected diseases, cytogenetic abnormalities are the most common, especially trisomy 21 (Down syndrome). Despite the improvement of ultrasound equipment and operators’ technique and the introduction of first and second maternal serum screening, fetuses with trisomy 21(Down syndrome) are still delivered unexpectedly due to lack of either significantly structural defects on prenatal ultrasound or abnormal maternal serum results. Karyotyping analysis on amniocytes has been considered to be a powerful tool to diagnose fetal trisomy 21 with the highest detection rate up to more than 99%, but amniocentesis is an invasive prenatal diagnosis which carries some risks (less than 1%) to pregnant woman including rupture of membranes, preterm uterine contractions and preterm labor.
In this study, we introduce a retrospective investigation of the 13-year experience on prenatal detection of aberrant karyotypes by amniocenetesis. Data were collected at China Medical University Hospital between Jan, 1995 and Dec, 2007 from prenatal cytogenetic analysis of cultured amniocytes. A total of 16315 cases were used to analyze chromosome aberrations on conventional cytogenetic procedures. Among these cases, 59.91% of cases were performed due to advanced maternal age, 22.36% for abnormal maternal serum Down screening results, 9.76% for abnormal ultrasound findings, 2.23% for positive family history and 5.64 for other reasons. Fetal chromosome aberrations were detected in 2.30% of cases. Numerical chromosome abnormalities were detected in 62.13% of these fetuses, including autosomal trisomies and sex chromosomal aneuploidies with mosaicism or non-mosaicism. The remaining chromosome aberrations were chromosomal structural abnormalities, including mosaic or non-mosaic and balanced or unbalanced translocation, insertion, deletion, inversion, and marker chromosomes.
Based on our data, the most common reason for the genetic amniocentesis is advanced maternal age. But it doesn’t detect the largest numbers of fetal chromosome aberrations. The addition of prenatal ultrasound and maternal serum screening in this group may be helpful in decreasing the numbers of unnecessary amniocentesis. For the effective use of amniocentesis as a diagnostic tool for fetal chromosome aberrations, we should make efforts to build up more efficient screening programs for pregnant women. In addition, our data could provide a database for appropriate genetic counseling for the
high risk group of pregnant women. |
