孕中期羊水细胞染色体核型分析及其异常核型发生率的比较

Karyotype analysis of amniotic fluid cells and comparison of chromosomal abnormality rate during second trimester

目的分析孕中期羊水细胞染色体核型及比较不同异常核型的发生率，并对各种异常核型的临床意义进行探讨。方法1998年9月至2010年11月在复旦大学附属妇产科医院集爱遗传与不育诊疗中心行羊水细胞染色体检查的孕妇共13648例，抽取并培养成功的羊水标本共计13795份，即13795个胎儿获得核型诊断，对上述胎儿根据其母亲（孕妇）不同检查指征进行分组：当孕妇年龄≥35岁时为高龄孕妇组（4065个）；血清学筛查提示高危时为血清筛查高危组（6462个）；超声筛查出现异常征象时为超声异常征象组（1539个）；已知夫妇中有一方为染色体异常时为夫妇染色体异常组（108个）；除此之外，其他胎儿列为其他因素组（1621个）。采用羊水细胞培养法对各组胎儿进行染色体核型分析，并用荧光原位杂交技术对78个≥26孕周的胎儿行常见非整倍体快速诊断，对153个核型异常胎儿的父母进行淋巴细胞核型分析。结果（1）各组异常核型分类及其构成：13795个胎儿中共发现异常核型388个，异常核型发生率为2．813％（388／13795）。388个异常胎儿中，非整倍体最多，为59．8％（232／388）；常染色体结构异常为24．7％（96／388）；嵌合体为12．4％（48／388）；其他较少见的异常核型包括标记染色体为1．3％（5／388），性染色体结构异常为1．0％（4／388），三倍体为0．8％（3／388）。除了夫妇染色体异常组，其他各组均以非整倍体占绝大多数，有4例罕见的非整倍体，分别出现在高龄孕妇组、超声异常征象组及血清筛查高危组。超声异常征象组异常核型种类最多，而夫妇染色体异常组其胎儿染色体异常种类最集中（常染色体结构异常）。嵌合体主要分布在血清筛查高危组，占该组异常核型的20．0％（29／145）。（2）异常核型种类及发生率：异常核型种类中以21三体最为常见，占全部异常核型的35．6％（138／388），其次为常染色体平衡性结构重排为20．6％（80／388）、嵌合体为12．4％（48／388）、18三体为11．3％（44／388），其他较常见的异常核型包括常染色体非平衡性结构重排和45，x0，各为4．1％（16／388），47，XXY为3．9％（15／388）。（3）父母淋巴细胞核型分析：153个胎儿进行了其父母淋巴细胞的核型分析，并最终确定了胎儿异常核型来源：家族性异常58个，新发生的异常95个。78个胎儿的荧光原位杂交技术诊断结果与G显带核型全部一致，其中2个为21三体。结论不同检查指征孕妇的胎儿异常核型的构成不同；孕中期胎儿异常核型种类繁多，致畸风险与异常核型种类有关。

Objective To investigate the karyotypes of amniotic fluid cells and compare the incidence of chromosomal abnormality as well as to evaluate the clinical significance of abnormal karyotypes. Methods A total of 13 648 pregnant women came to Shanghai Jiai Genetics and IVF Institute, Obstetrics and Gynecology Hospital, Fudan University to do amniocentesis from September 1998 to November 2010, and 13 795 amniotic fluid specimens were successfully extracted and cultured, thus 13 795 fetuses received karyotype diagnosis. These fetuses were grouped according to different indications. If maternal age was ≥ 35, the fetuses were grouped into the advanced maternal age group （4065） ; and if maternal serum screening test revealed high-risk of trisomy 18 or trisomy 21, the fetuses were grouped into the high-risk serum screening group （6462） ; and those with abnormal signs of ultrasound screening were grouped into the abnormal ultrasound signs group （1539） ; and if either of the parents was with chromosome abnormalities, the fetus was grouped into the paternal/maternal abnormality group （ 108 ） ; whereas the remainder were grouped in other factors group （ 1621 ）. The amniotic fluid cells were in-situ cultured on coverslips, harvested by conventional G-banded methods, and then analyzed by two doctors. In order to get rapid diagnosis, some pregnant women whose gestational age ≥26 weeks accepted fluorescense in situ hybridization （FISH）. FISH was done on 78 uncultured amniotic fluid specimens using probes located at chromosome 13,18,21, X, Y. Some parents were required to analyze lymphocyte karyotype to help judging the origin of abnormal karyotype. Results （ 1 ） Classification and composition of abnormal karyotypes in each group ： a total of 388 abnormal karyotypes were found among 13 795 fetuses, and the abnormal rate was 2. 813% （388/13 795）. Of the 388 fetuses, aneuploidy was the most common pattern which was up to 59.8% （232/388）; autosomal structural abnormality rate was 24. 7% （ 96/388 ） ; mosaicism was 12.4% （ 48/388 ）. Other uncommon abnormal karyotypes included marker chromosome （5/388,1.3%） , sex chromosomal structural abnormality （4/388,1.0%） and triploid （3/388, 0. 8% ）. Aneuploidy was the most common in most groups except the paternal/maternal abnormality group. There were four cases of rare aneuploid in the advanced maternal age group, the high-risk serum screening group and the abnormal ultrasound signs group respectively. Every type of abnormality could be found in the abnormal ultrasound signs group, and autosomal structural abnormalities were concentrated in paternal/maternal abnormality group. Mosaicism mainly distributed in the high-risk serum screening group, accounting for 20. 0% （29/145） of abnormalities in this group. （2） Abnormal types and the incidence： the most common type was trisomy 21 （ 138/388,35.6% ）, fallowed by autosomal balanced structural rearrangements（80/388, 20. 6% ）, mosaicism （48/388,12. 4% ） and trisomy 18 （44/388,11.3 % ）. Others included non-balanced autosomal structural rearrangements （ 16/ 388,4. 1% ）, 45 ,X0 （16/388,4. 1% ） and 47 ,XXY（ 15/388,3.9% ）. （3） Lymphocyte karyotype analysis of the couples： parents of 153 fetuses were analyzed to determine the origin of abnormal karyotype. Fifty-eight familial and 95 de novo abnormalities were found. FISH results were the same with G-banding karyotype, and two of these were trisomy 21. Conclusions Abnormal karyotype composition is different according to different maternal amniocentisis indications. There is a variety of abnormal karyotypes in the second trimester pregnancy, and the risk of fetal malformation is related with the kind of abnormal karyotype.