探讨染色体微阵列分析(CMA)技术在全基因组水平探讨股骨长度(FL)偏短胎儿的遗传学病因。

选取2019年1月至2020年12月于广州市妇女儿童医疗中心经产前胎儿超声检查提示胎儿FL偏短，并接受侵入性产前诊断的73例孕妇及其胎儿为研究对象。根据是否合并其他明显结构异常，将其分为孤立组(n＝56，单纯FL或四肢长骨短于同胎龄儿，较正常值<－2 s，伴或不伴超声软指标阳性者)和复杂组[n＝17，合并骨骼系统其他畸形和(或)其他系统结构畸形者]。对这73例胎儿进行染色体核型分析和CMA检测，并应用染色体分析套件(ChAS)及相关的生物信息学方法对结果进行分析。本研究遵循的程序符合广州市妇女儿童医疗中心人体试验委员会所制定的伦理学标准，得到该伦理委员会批准(审批文号：穗妇儿科伦通字〔2019〕第11600号)。所有孕妇在接受侵入性产前诊断前及接受遗传咨询时，均签署知情同意书，并告知产前诊断风险、检测优势及局限性。

①孤立组56例胎儿中，6例合并超声软指标异常；复杂组17例胎儿中，6例合并神经系统畸形，6例合并心血管畸形，6例合并其他骨骼系统畸形。②这73例胎儿CMA检测结果中，10例含有致病性/可能致病性染色体拷贝数变异(CNV)，总致病性检出率为13.7%(10/73)，临床意义不明变体(VUS) CNV检出率为2.7%(2/73)，其中非致病CNV检出率为83.6%(61/73)。③44例同时接受染色体核型分析和CMA检测的FL偏短胎儿中，孤立组为34例，复杂组为10例。复杂组中，染色体核型异常率(10.0%)和CMA技术检出异常率(30.0%)比较，差异无统计学意义(χ²＝2.08，P＝0.149)，④这73例胎儿均未检出含有已知FGFR3基因的致病性位点突变。其中63例CMA技术检出结果呈阴性胎儿中，7例因产前超声检测高度怀疑为长骨发育不良(四肢长骨较同胎龄儿正常值<－3 s)，进一步进行全外显子组测序(WES)检测结果显示，1例胎儿检测到COL1A1基因突变(c.2519C>T; p．P840L)，判断为VUS者。⑤随访结果显示，31例(42.5%)胎儿足月分娩，15例(48.4%)活产儿在婴儿期出现生长速率为同龄儿正常值的第10百分位数，其他发育评估指标未见明显异常。

CMA技术在产前诊断FL偏短胎儿具有一定应用价值，并且检出率较染色体核型分析更高。建议临床将CMA作为一线检测技术，应用于产前超声检查提示FL偏短胎儿中，尤其是应用于合并其他结构异常者中。

To explore the genetic etiology of fetuses with short femur length (FL) at the genome-wide level by chromosome microarray analysis (CMA) technique.

Seventy-three pregnant women and their fetuses who had short FL by prenatal ultrasonography and underwent invasive prenatal diagnosis at Guangzhou Women and Children′s Medical Center from January 2019 to December 2020 were enrolled in the study. According to whether they were combined with other obvious structural developmental abnormalities, they were divided into isolated group (n=56) and complex group (n=17). Chromosomal karyotyping and CMA were performed, and results were analyzed by applying CHAS software and related bioinformatics methods. The procedures followed in this study were in accordance with the ethical standards set by the Human Experimentation Committee of Guangzhou Women and Children′s Medical Center, and were approved by this ethical committee (Approval No. [2019] 11600). Written informed consents were obtained form all pregnant women.

① Of these 56 fetuses in isolated group, 6 were combined with ultrasound soft index abnormalities; of these 17 fetuses in complex group, 6 were combined with neurological malformations, 6 with cardiovascular malformations, and 6 with malformations of other skeletal systems. ②The CMA results of 73 fetuses showed that 10 cases contained pathogenic/probably pathogenic copy number variants (CNV), with a total pathogenicity detection rate of 13.7% (10/73), the variants of uncertain significance (VUS) detection rate of 2.7% (2/73), and a benign CNV detection rate of 83.6% (61/73). ③Of the 44 short FL fetuses that underwent both chromosomal karyotyping and CMA testing, 34 were in isolated group and 10 were in complex group. Comparison of the rates of chromosomal karyotype abnormality (10.0%) and abnormal detection by CMA technique (30.0%) in the complex group showed no statistically significant difference (χ²=2.08, P=0.149). ④None of the 73 fetuses were found to contain the known pathogenic locus of FGFR3 gene. Of the 63 CMA-negative fetuses, 7 fetuses were highly suspected of having long-bone dysplasia due to prenatal ultrasonography (long bones of the limbs <3% of the children of the same gestational age), and further whole exome sequencing (WES) testing showed that the COL1A1 mutation (c.2519C>T; p. P840L) was detected in 1 fetus as VUS. ⑤Follow-up showed that 31 (42.5%) fetuses were delivered at term, 15 (48.4%) live births showed a growth rate of long below the 10th percentile of the same-age child in infancy, and other developmental assessments did not show any obvious abnormalities.

CMA has a certain application value in prenatal diagnosis of fetuses with short FL and has a higher detection rate than chromosomal karyotyping. Therefore, it is suggested that CMA should be used as a first-line technique in the prenatal diagnosis of fetuses with short FL on prenatal ultrasound examination, especially when combined with other structural abnormalities.