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Table 1 Characteristics of study population

From: Investigation on combined copy number variation sequencing and cytogenetic karyotyping for prenatal diagnosis

Characteristic Study population (n = 9452)
Maternal age (years) 31 (27–36)
Advanced maternal age (≥ 35 yrs) 3142 (33.2)
Nation
 Han 6593 (69.8)
 Yi 822 (8.7)
 Bai 433 (4.6)
 Dai 282 (3.0)
 Hui 250 (2.6)
 Zhuang 167 (1.8)
 Naxi 145 (1.5)
 Hani 112 (1.2)
 Others 648 (6.8)
Parity
 Nulliparous 3457 (36.6)
 Parous 5995 (63.4)
   = 1 5355 (56.7)
   = 2 567 (6.0)
   ≥ 3 64 (0.7)
Gestational age at invasive diagnosis (weeks) 20 (19–21)
Invasive prenatal diagnosis procedure
 Amniocentesis 8855 (93.7)
 Cordocentesis 552 (5.8)
 Chorion villus sampling 44 (0.5)
Maternal or/and paternal chromosome abnormalities 155 (1.6)
History of bearing child with chromosome abnormalities 203 (2.1)
Indications for invasive prenatal diagnosis
 NIPT high-risk 415 (4.4)
 Maternal serum screening high-risk 1984 (21.0)
  DS high-risk 2999 (31.7)
  ES high-risk 799 (8.5)
  Both DS and ES high-risk  
 Advanced maternal age (≥ 35 yrs) 1177 (12.5)
 Abnormal fetal ultrasonography 1229 (13.0)
  Grade 1 1857 (19.6)
  Grade 2 1549 (16.4)
  Grade 3 531 (5.6)
  Grade 4 219 (2.3)
 Other indications 831 (8.8)
  ≥ two indications 3816 (40.4)