双胎妊娠合并结构异常染色体核型异常的临床特征

Zhong Shi-lin, Fang Qun, Chen Bao-jiang, Han Zhen-yan, Luo Yan-min, Chen Jian-sheng, Xie Ying-jun

Department of Obstetrics and Gynecology, Sun Yat-Sen University, Guangzhou, China.

Zhonghua Fu Chan Ke Za Zhi. 2011 Sep;46(9):649-54.

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 examined 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%, 13/205), 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 phenotypes. The results suggest that it is necessary to analyze both karyotypes of twins even if only one fetus is complicated with structural abnormalities.

目的

探讨双胎妊娠合并胎儿畸形时染色体核型异常的临床特征。

方法

选取2000年1月至2010年9月在中山大学附属第一医院就诊的181例双胎妊娠（362例胎儿），其中1个或2个胎儿经超声诊断有异常。根据以下因素分组：（1）孕妇年龄：孕妇年龄≥35岁者分为高龄妊娠组（105例胎儿），孕妇年龄<35岁者分为低龄妊娠组（203例胎儿）；（2）受孕方式：经辅助生殖技术受孕者分为辅助生殖组（81例胎儿），自然受孕者分为自然受孕组（227例胎儿）；（3）绒毛膜性：单绒毛膜双胎（MCT）妊娠分为MCT组（123例胎儿），双绒毛膜双胎（DCT）妊娠分为DCT组（185例胎儿）；（4）结构异常：205例有结构异常的胎儿分为异常胎儿组，103例无结构异常的胎儿分为正常胎儿组。所有胎儿均行超声检查，308例胎儿行染色体检查。

结果

（1）胎儿核型：181例双胎妊娠中，23例（12.7%，23/181）1个或2个胎儿有染色体异常，23例中的20例对两个胎儿均进行了染色体检查。308例胎儿中26例（8.4%，26/308）染色体异常，非整倍体是最常见的异常核型类型（53.8%，14/26）。205例畸形胎儿中21例（10.2%，21/205）染色体异常。（2）MCT组123例胎儿中7例（5.7%，7/123）染色体异常，DCT组185例胎儿中19例（10.3%，19/185）染色体异常。两组染色体异常发生率无统计学差异。DCT组有14例非整倍体胎儿（7.6%，14/185）；MCT组无非整倍体胎儿。两组间有统计学差异。DCT组2例中，因另1个胎儿死亡仅对1个畸形胎儿进行了染色体检查，核型分别为21三体和18三体。其余17例的两个胎儿均进行了染色体检查，每次妊娠两个胎儿的染色体均不同。DCT组19例染色体异常胎儿中15例合并结构异常，MCT组4例双胎妊娠中的7例胎儿有染色体异常。（3）高龄妊娠组与低龄妊娠组异常核型发生率比较：高龄妊娠组异常核型发生率为7.6%（8/105），低龄妊娠组为8.9%（18/203）。两组间无统计学差异（P>0.05）。高龄妊娠组105例胎儿中6例为非整倍体（5.7%，6/105），低龄妊娠组203例胎儿中8例为非整倍体（3.9%，8/203）。高龄妊娠组非整倍体发生率显著高于低龄妊娠组（P<0.05）。（4）辅助生殖组与自然受孕组异常核型发生率比较：辅助生殖组81例胎儿中11例（13.6%，11/81）染色体异常，自然受孕组227例胎儿中15例（6.6%，15/227）染色体异常。两组间有统计学差异（P<0.05）。辅助生殖组有7例非整倍体胎儿（8.6%，7/81），自然受孕组有7例非整倍体胎儿（3.1%，7/227），无统计学差异（P>0.05）。（5）异常胎儿组与正常胎儿组异常核型发生率比较：异常胎儿组205例胎儿中21例（10.2%，21/205）染色体异常，正常胎儿组103例胎儿中5例（4.9%，5/103）染色体异常。无统计学差异（P>0.05）。异常胎儿组13例为非整倍体（6.3%，13/205），正常胎儿组仅1例为非整倍体（1.0%，1/103）。两组间有统计学差异（P<0.05）。