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J Hum Genet. 2015 Mar;60(3):133-7. doi: 10.1038/jhg.2014.116. Epub 2015 Jan 8.

Chromosome abnormalities diagnosed in utero: a Japanese study of 28 983 amniotic fluid specimens collected before 22 weeks gestations.

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Department of Maternal-Fetal, Neonatal and Reproductive Medicine, National Center for Child Health and Development, Tokyo, Japan.
Department of Companion Diagnostics, LabCorp Clinical Trials, Laboratory Corporation of America Holdings, Burlington, NC, USA.
Department of Obstetrics and Gynecology, Showa University, Tokyo, Japan.
Department of Obstetrics and Gynecology, Hyogo College of Medicine, Nishinomiya, Japan.
Department of Obstetrics and Gynecology, Saitama Medical University, Saitama, Japan.


To investigate the frequency and type of abnormal karyotype in Japan by amniocentesis before 22 weeks of gestation. We performed a retrospective analysis of 28 983 amniotic fluid specimens in a local population collected before 22 weeks gestations for fetal karyotyping. The incidence of abnormal karyotype was 6.0%. The main indication was advanced maternal age (AMA) of 35 years and older, which represented over half of the clinical indications. Abnormal karyotype was most frequently reported among the referrals for abnormal ultrasound findings (21.8%), followed by positive maternal serum screen results (5.3%). Three-fourths of abnormal karyotype was either autosomal aneuploidy (64.0%) or sex chromosome aneuploidy (11.6%). Abnormal karyotype was detected in 2.8% of pregnant women referred for AMA. Clinically significant abnormal karyotype increased with advancing maternal age. The frequency and type of abnormal karyotype detected by amniocentesis for various indications were determined. Amniocentesis was mainly performed among the referrals for AMA, which is a characteristic distribution of indications of Japan.

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