双胎妊娠中结构异常胎儿染色体核型异常的临床特征

目的：探讨双胎妊娠中结构异常胎儿的染色体核型异常的临床特征。方法2000年1月-2010年9月,中山大学附属第一医院就诊的双胎妊娠孕妇181例（共362个胎儿）,对其中介入性产前诊断的308个胎儿按不同因素分组如下。(1)按孕妇年龄分组：≥35岁孕妇（105个胎儿）为高龄孕妇组;＜35岁孕妇（203个胎儿）为适龄孕妇组。(2)按受孕方式分组：辅助生育孕妇（81个胎儿）为辅助生育组,自然受孕（227个胎儿）为自然受孕组。(3)按绒毛膜性质分组：单绒毛膜双胎（MCT,123个胎儿）为MCT组,双绒毛膜双胎（DCT,185个胎儿）为DCT组。(4)按结构异常分组：205个结构异常胎儿为异常胎儿组,103个正常胎儿为正常胎儿组。对362个胎儿进行超声检查并对其中的308个双胎胎儿行染色体核型分析。结果(1)胎儿染色体核型分析结果：181例双胎孕妇中检出胎儿核型异常23例(12.7％,23/181),核型异常的23例双胎孕妇中,20例检查了两个胎儿的核型。308个胎儿中检出异常核型的胎儿26个(8.4％,26/308),以非整倍体最多见,占异常核型的53.8％ (14/26)。205个异常胎儿中21个有染色体核型异常(10.2％,21/205);103个正常胎儿中5个有染色体异常(4.9％,5/103),两者比较,差异无统计学意义(P＞0.05)。(2)MCT组和DCT组胎儿染色体核型异常发生率比较：MCT组123个胎儿中7个有染色体异常,发生率为5.7％ (7/123);DCT组185个胎儿中19个有染色体异常,发生率为10.3％( 19/185),两组胎儿的染色体异常发生率比较,差异无统计学意义(P＞0.05)。在染色体异常类别中,DCT组有14个胎儿为非整倍体异常,非整倍体率为7.6％(14/185),而MCT组无一例发生,两组比较,差异有统计学意义(P＜0.05)。DCT组中,两例双胎中因l胎死亡仅检查有结构异常的另一个活胎,分别为21三体和18三体;其余17例均分别检查了两个胎儿,两个胎儿的染色体核型不相同。DCT组19个核型异常的胎儿中,15个胎儿超声检查提示为结构异常(15/19)。MCT组中,4例双胎中有7个胎儿检出染色体异常。(3)高龄孕妇组和适龄孕妇组胎儿染色体异常发生率比较：高龄孕妇组胎儿的染色体异常发生率为7.6％(8/105),适龄孕妇组为8.9％( 18/203),两组比较,差异无统计学意义(P＞0.05);在染色体异常类别中,高龄孕妇组6个胎儿为非整倍体异常(5.7％,6/105),适龄孕妇组仅8个胎儿(3.9％,8/203),高龄孕妇组胎儿的非整倍体率显著高于适龄孕妇组,差异有统计学意义(P＜0.05)。(4)辅助生育组和自然受孕组胎儿染色体异常发生率比较：辅助生育组81个胎儿中有l1个染色体异常(13.6％,11/81),自然受孕组227个胎儿中有15个染色体异常(6.6％,15/227),差异有统计学意义(P＜0.05)。在染色体异常类别中,辅助生育组7个胎儿为非整倍体异常(8.6％,7/81),自然受孕组也为7个胎儿(3.1％,7/227),差异无统计学意义(P＞0.05)。(5)异常胎儿组和正常胎儿组染色体异常发生率比较：异常胎儿组205个胎儿中有21个染色体异常(l0.2％,21/205),正常胎儿组103个胎儿中有5个染色体异常(4.9％,5/103),两组比较,差异无统计学意义(P＞0.05);在染色体异常类别中,异常胎儿组13个胎儿为非整倍体异常(6.3％,13/205),正常胎儿组仅1个胎儿(1.0％,1/103),两组比较,差异有统计学意义(P＜0.05)。结论非整倍体是双胎合并胎儿结构异常时最常出现的染色体异常,以21三体最为常见。双胎之间的核型不一致和双胎之一出现非整倍体的情况常见于DCT,而MCT时两个胎儿核型往往一致,但两个胎儿发生相同的染色体异常可能出现不同的表型;双胎之一合并胎儿结构异常时,建议分别对两个胎儿同时行染色体核型分析。

Clinical features of abnormal chromosome karyotypes in twin pregnancies complicated with structural abnormalities

Objective To investigate the clinical features of the abnormal chromosome karyotypes in twin pregnancies complicated with fetal malformations. Methods Totally 181 twin pregnancies (362 fetuses) in which one or two fetuses had abnormalities diagnosed by ultrasound were referred to the First Affiliated Hospital of Sun Yat-Sen University from January, 2000 to September, 2010. They were divided into different groups according to ( 1 ) maternal age: the cases with maternal age ≥35 were divided into advanced pregnancy group ( 105 fetuses) , and those with maternal age ＜35 were divided into young pregnancy group (203 fetuses) ; ( 2 ) conceived method : those conceived by assisted reproductive technology were divided into assisted reproductive group (81 fetuses), and the natural conception pregnancies were divided into natural conception group (227 fetuses) ; ( 3 ) chorionicity: the monochorionic twin (MCT) pregnancies were divided into MCT group( 123 fetuses), and the dichorionic twin (DCT) pregnancies were divided into DCT group( 185 fetuses); (4) structural abnormalities: 205 fetuses with structural abnormalities were divided into the abnormal fetal group, and 103 fetuses without structural abnormalities were divided into the normal fetal group. All fetuses were examined by the ultrasound and chromosomes were examined in 308 fetuses. Results ( 1 ) The karyotype of fetuses: among 181 twin pregnancies, 23 cases had chromosomal abnormalities in 1 or 2 fetuses ( 12. 7％ ,23/181 ), and chromosomes were exarmined in both fetuses in 20 of 23 cases. Twenty-six of 308 fetuses were found with abnormal chromosomes ( 8.4％, 26/308 ) , and the aneuploid was the most common type of abnormal karyotypes ( 53.8％ , 14/26 ). Twenty-one of 205 fetuses with malformations were found with abnormal karyotypes (10. 2％, 21/205 ). (2) Seven of 123 fetuses in MCT group were with abnormal karyotypes (5.7％, 7/123), and 19 of 185 fetuses in DCT group were with abnormal karyotypes ( 10. 3％, 19/185 ). There was no statistical difference of abnormal chromosome incidence between the two groups. There were 14 fetuses with aneuploid in DCT group ( 7.6％, 14/185 ) ;but there was no fetus with aneuploid in MCT group. There was statistical difference between these two groups. In two cases of DCT group, only one fetus with malformation received chromosome examination because another fetus was dead, and the karyotypes were trisomy 21 and trisomy 18 respectively. Both fetuses of the rest 17 cases received chromosome examination, and the chromosomes of both fetuses in each pregnancy were different. Fifteen of 19 fetuses with abnormal chromosomes in DCT group were complicated with structural abnormalities, and 7 fetuses of 4 twin pregnancies in MCT group were with chromosomal abnormalities. (3) The comparison of the abnormal karyotype incidence between the advanced pregnancy group and young pregnancy group: the abnormal karyotype incidence of the advanced pregnancy group was 7. 6％ (8/105), and that was 8.9％ (18/203) in young pregnancy group. There was no statistical difference between the two groups ( P ＞ 0. 05 ). Six of 105 fetuses in advanced pregnancy group were aneuploids (5. 7％, 6/105), and 8 of 203 fetuses in young pregnancy group were aneuploids (3.9％, 8/203). The aneuploid incidence in advanced pregnancy group was significantly higher than that in young pregnancy group ( P ＜ 0. 05 ). (4) The comparison of the abnormal karyotype incidence between the assisted reproductive group and the natural conception group: 11 of 81 fetuses were with the abnormal karyotypes in assisted reproductive group ( 13. 6％, 11/81 ), and 15 of 227 fetuses were with the abnormal karyotypes in assisted reproductive group (6. 6％, 15/227). There was statistical difference between the two groups ( P ＜0. 05). There were 7 fetuses with the aneuploid in assisted reproductive group ( 8. 6％, 7/81 ) and 7 fetuses with the aneuploid in natural conception group ( 3. 1％, 7/227 ), which showed no statistical difference ( P ＞0. 05 ).(5) The comparison of the abnormal karyotype incidence between the abnormal fetal group and normal fetal group: 21 of 205 fetuses in abnormal fetal group were with abnormal karyotypes (10. 2％, 21/205), and 5 of 103 fetuses in normal fetal group were with abnormal karyotypes ( 4. 9％, 5/103 ) . There was no statistical difference (P ＞ 0. 05 ). 13 fetuses in abnormal fetal group were with the aneuploid (6. 3％, 1 3/205), and only one fetus in normal fetal group was aneuploid (1.0％, 1/103 ). There was statistical difference between the two groups ( P ＜ 0. 05 ). Conclusions Aneuploid is the most common abnormal karyotype in twin pregnancy complicated with fetal abnormalities, especially trisomy 21. Aneuploid mainly occurs in only one fetus of DCT, and chromosomal discordance is usually found in DCT. While in MCT, the twin fetuses with the same abnormal karyotype may have different pbenotypes. The results suggest that it is necessary to analyze both karyotypes of twins even if only one fetus is complicated with structural abnormalities.