探讨18-三体综合征(TS)胎儿中孕期超声检查结果与染色体核型分析结果。

选择2015年1月至2020年12月，在云南省第一人民医院医学遗传科通过羊膜腔穿刺术和脐血取样，被确诊为18-TS的175例胎儿为研究对象。采用回顾性分析方法，对这175例胎儿的中孕期超声检查结果、染色体核型结果进行分析。本研究遵循的程序符合2013年新修订的《世界医学协会赫尔辛基宣言》要求。

本组175例18-TS胎儿分析结果如下。①产前诊断指征：中孕期胎儿超声表现异常为169例(96.6%)；86例早孕期血清学筛查提示18-TS高风险为78例(90.7%)；106例进行胎儿游离DNA无创产前筛查(NIPT)，提示18-TS高风险为99例(93.4%)；孕母高龄(预产期年龄≥35岁)为79例(45.1%)；1例(4.7%)为地中海贫血高风险(胎儿父母均为α地中海贫血)。102例(58.3%)胎儿同时合并≥2项上述产前诊断指征。②中孕期超声检查结果：169例(96.6%)检查结果异常，6例(3.4%)未见异常。其中，157例(89.7%)超声异常≥2项，最常见结构异常为心脏畸形(131例、74.9%)，肢体畸形(113例、64.6%)，面部畸形(67例、38.3%)和中枢神经系统异常(54例、30.9%) 4类，特别是室间隔缺损(70例、40.0%)，钩状手(35例、20.0%)，小下颌(43例、24.6%)及草莓头(33例、18.9%) 4种；最常见超声软指标异常为脉络膜囊肿(116例、66.3%)与单脐动脉(54例、30.9%)。③胎儿染色体核型分析结果：18-三体为167例(95.4%)，染色体嵌合型为5例(2.9%)，合并其他染色体核型异常为3例(1.7%)。167例18-三体胎儿中，胎儿超声可见结构异常≥2项为150例(89.8%)，软指标异常为11例(6.6%)，超声未见异常者为6例(3.6%)。5例染色体嵌合胎儿中，胎儿超声可见结构异常≥2项为3例，软指标异常项为2例。3例合并其他染色体核型异常胎儿中，胎儿超声可见结构异常≥2项为2例，软指标异常为1例。

18-TS胎儿多伴有多种超声结构异常。中孕期超声检查可作为18-TS胎儿的产前筛查重要手段。

To explore results of ultrasonographic and chromosome karyotype of fetuses with 18-trisomy syndrome (TS) during the second trimester pregnancy.

A total of 175 fetuses diagnosed as 18-TS after amniotic fluid puncture or umbilical cord blood puncture in Department of Medical Genetics of the First People′s Hospital of Yunnan Province from January 2015 to December 2020 were selected as research subjects. Ultrasonographic results during the second trimester pregnancy and results of chromosome karyotype analysis of those 175 fetuses were analyzed by retrospective method. The procedures in this study were in line with the requirements of World Medical Association Declaration of Helsinki revised in 2013.

Related results of the 175 fetuses with 18-TS were as follows. ①Indications of prenatal diagnosis: 169 cases (96.6%) had abnormal ultrasonographic results during the second trimester pregnancy. 86 cases received serology screening in the first trimester, and there were 78 cases (90.7%) of high risk of 18-TS. Noninvasive prenatal testing (NIPT) of fetal free DNA in 106 cases indicated a high risk of 18-TS in 99 cases (93.4%). 79 cases (45.1%) with advanced maternal age (age at expected date of confinement≥35 years). One case (4.7%) had high risk of Thalassemia (both parents were α-Thalassemia). There were 102 cases (58.3%) of fetuses with ≥2 items of the above-mentioned prenatal diagnostic indications.②Ultrasonographic results during the second trimester pregnancy: 169 cases (96.6%) with abnormal results, and 6 cases (3.4%) showed no abnormalities. 157 cases (89.7%) had two or more ultrasound abnormalities. The most common 4 ultrasonographic structural abnormalities were heart malformations (131 cases, 74.9%), limb malformations (113 cases, 64.6%), facial malformations (67 cases, 38.3%) and central nervous system abnormalities (54 cases, 30.9%). And the most common abnormalities of those 4 abnormalities were ventricular septal defect (70 cases, 40.0%), hook-shaped hand (35 cases, 20.0%), small jaw (43 cases, 24.6%), and strawberry head (33 cases, 18.9%). Choroidal cyst (116 cases, 66.3%) and single umbilical artery (54 cases, 30.9%) were most common abnormalities of ultrasonographic soft indexes. ③Results of fetal karyotype analysis: 167 cases (95.4%) were complete trisomy 18, 5 cases (2.9%) were mosaic trisomy 18, and 3 cases (1.7%) were other karyotype abnormality. In 167 cases of fetuses with complete 18-trisomy, 150 cases (89.8%) had ≥2 structural abnormalities, 11 cases (6.6%) had abnormalities in soft indexes, and 6 cases (3.6%) with no abnormality. Among the 5 cases of mosaic trisomy 18, 3 cases with ≥2 structural abnormalities and 2 cases showed abnormality in soft indexes. Among the 3 fetuses with other chromosomal karyotype abnormalities, 2 cases showed ≥2 structural abnormalities and 1 case showed abnormality in soft indexes.

The fetuses with 18-TS are often combined with a variety of ultrasound structural abnormalities. The second trimester ultrasonography can be used as an important auxiliary means of prenatal screening of fetuses with 18-TS.