探讨产前诊断技术在18-三体综合征胎儿产前诊断中的临床应用现状。

选取2010年1月至2014年8月于广州市妇女儿童医疗中心产前诊断中心接受介入性产前诊断的13 354例孕妇中，检出的95例18-三体综合征胎儿为研究对象。产前诊断方法为胎龄为11～13^＋6孕周行绒毛活检术，胎龄为16～24孕周行羊膜腔穿刺术，胎龄>24孕周后行经皮脐血穿刺术。对95例胎儿的产前诊断指征、胎儿染色体异常核型及超声异常表现进行分析。本研究遵循的程序符合广州市妇女儿童医疗中心制定的伦理学标准，得到该委员会批准，介入性产前诊断的所有操作均获得孕妇及其家属的知情同意，并与之签署临床研究知情同意书。

①穿刺情况：95例孕妇中，46例(48.4%)于早孕期筛查结果异常，47例(48.4%)于中、晚孕期筛查结果异常，1例为夫妇双方α地中海贫血基因携带者(东南亚缺失型)于早孕期行绒毛活检术提示18-三体综合征高风险，1例于中孕期行产前无创染色体非整倍体检测结果提示18-三体综合征高风险。95例孕妇中，33例(34.7%)接受绒毛活检术，46例(48.4%)接受羊膜腔穿刺术和16例(16.7%)接受脐血穿刺术。②胎儿染色体核型分析结果：91例(95.8%)为单纯型和4例(4.2%)为嵌合体型18-三体综合征，4例嵌合体型中，2例异常核型比例超过20%，早孕期超声检查提示异常；1例嵌合比例11.0%，中孕期血清学筛查提示高风险；1例嵌合8.0%，于早、中孕期检查均未见异常，晚孕期超声检查提示胎儿生长发育迟缓后经产前诊断证实。③超声表现：38例(82.6%)孕妇于早孕期经超声检查提示胎儿异常，主要表现为胎儿颈项透明层(NT)增厚或胎儿合并多发畸形；40例(95.2%)孕妇于中、晚孕期经超声检查提示胎儿异常，其中36例(90.0%)合并2种或以上畸形。

早孕期产前筛查有助于早期诊断18-三体综合征，血清学筛查联合超声检查对18-三体综合征的产前诊断具有重要意义。

To assess clinical application of prenatal diagnosis in trisomy 18 during pregnancy.

A total of 13 354 cases received invasive prenatal diagnosis at Prenatal Diagnosis Center, Guangzhou Woman and Children's Medical Center between January 2010 and August 2014. Among them, 95 fetus were diagnosed as trisomy 18. Three prenatal diagnostic methods included chorionic villi biopsy (11-13^{+ 6} gestational weeks), amniocentesis (16-24 gestational weeks) and percutaneous puncture of umbilical cord (>24 gestational weeks). The indications of prenatal diagnosis, abnormal karyotype of chromosome of fetus, and ultrasonic abnormal manifestations of 95 cases with trisomy 18 were analyzed. The study protocol was approved by the Ethical Review Board of Investigation in Human Being of Guangzhou Woman and Children's Medical Center. Informed consent was obtained from each participates.

① Indications: 46 cases (48.5%) of 95 cases were high risk in the first trimester screening, 47 cases (48.4%) were high risk in the second and third trimester, the remaining 2 cases of indications were high risk in non-invasive prenatal test (NIPT) and carriers of α-thalassemia.Furthermore, among 95 cases with trisomy 18, 33 pregnant women underwent chorionic villi biopsy, 46 underwent amniocentesis, and other 16 underwent percutaneous puncture of umbrlical cord. ② Chromosome karyotypes: except of 91 cases (95.8%) simple karyotype of trisomy 18, 4 cases (4.2%) were chromosome mosaic. Among them, 2 cases of mosaic ratio than 20% were found structure abnormalities in the first trimester screening. One in 11.0% was high risk in the second trimester screening. One in 8.0% had no findings in the first and second trimester screening, while had fetal growth restriction (FGR) in the third trimester. ③ The main ultrasound findings in the first trimester of 38 cases (82.6%) were nuchal translucency (NT) thickening, nasal bone absence or hypoplasia, cystic hygroma, omphalocele and anencephaly, another 40 cases (95.2%) were found abnormal in the second or third trimester, mainly were multiple malformations especially for cardiac anomaly.

The prenatal diagnosis during the first trimester is helpful in diagnosing of trisomy 18, and the combination of serum markers test and ultrasonography is very important to the prenatal diagnosis of trisomy 18.