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Table 1 Background characteristics of participants by mode of conception

From: Complications and adverse outcomes in pregnancy and childbirth among women who conceived by assisted reproductive technologies: a nationwide birth cohort study of Japan environment and children’s study

  Natural conception OI without ART Conventional IVF-ET ICSI
N = 90,506 N = 3939 N = 1476 N = 1671
  Median IQR Median IQR Median IQR Median IQR
Maternal age (years) 31 8 33 6 36 6 36 6
 Missing (N) 733 31 4 17
Maternal height (cm) 158.0 8.0 158.0 7.5 158.7 8.0 158.5 7.0
 Missing (N) 477 23 3 6
Maternal BMI before pregnancy (kg/m2) 20.6 3.5 20.6 3.7 20.7 3.4 20.7 3.3
 Missing (N) 1089 41 15 17
Maternal weight before delivery (kg) 62.3 10.6 62.1 11.1 62.4 10.6 61.8 10.5
 Missing (N) 3019 158 55 79
  N % N % N % N %
Parity
 0 33,760 38.2 2290 59.9 949 66.0 1089 68.1
 1 34,934 39.5 1331 34.8 447 31.1 469 29.3
 2 or more 19,712 22.3 201 5.3 42 2.9 42 2.6
 (Missing) 2100   117   38   71  
Prior cesarean section
 No 82,242 90.9 3680 93.5 1346 91.2 1530 91.6
 Yes 8200 9.1 257 6.5 130 8.8 141 8.4
 (Missing) 64   2   0   0  
Marital status
 Married 85,789 95.2 3919 99.6 1474 100.0 1668 99.8
 Single 4304 4.8 16 0.4 0 0.0 3 0.2
 (Missing) 413   4   2   0  
Pre-existing maternal condition
 No 74,963 85.4 3080 81.3 1087 75.3 1242 77.6
 Yes 12,858 14.6 710 18.7 357 24.7 359 22.4
 (Missing) 245   4   1   3  
Folic acid supplementation
 No 47,803 53.0 1310 33.3 470 31.9 476 28.5
 A few times per month 4610 5.1 184 4.7 38 2.6 52 3.1
 A few times per week 14,127 15.7 735 18.7 251 17.0 293 17.6
 Daily 23,721 26.3 1706 43.4 716 48.5 847 50.8
 (Missing) 695   21   8   7  
Maternal smoking during pregnancy
 No 85,152 94.8 3867 98.7 1453 99.0 1649 99.1
 Yes 4659 5.2 51 1.3 15 1.0 15 0.9
 (Missing) 440   10   3   3  
Maternal drinking during pregnancy
 No 81,033 90.0 3579 91.1 1362 92.5 1525 91.4
 Yes 9033 10.0 350 8.9 111 7.5 143 8.6
 (Missing) 2512   100   38   42  
Maternal educational level
 Junior high/high school 33,026 37.5 904 23.5 335 23.3 358 22.0
 Vocational school/junior college 36,499 41.5 1866 48.6 673 46.8 777 47.7
 University/graduate school 18,469 21.0 1069 27.8 430 29.9 494 30.3
 (Missing) 1902   47   15   23  
Paternal smoking
 No 45,916 51.8 2464 63.3 977 66.9 1145 69.5
 Yes 42,688 48.2 1428 36.7 484 33.1 503 30.5
 (Missing) 3105   105   39   45  
Paternal educational level
 Junior high/high school 39,601 45.3 1229 32.1 475 33.1 503 30.9
 Vocational school/junior college 19,687 22.5 902 23.5 272 18.9 351 21.6
 University/graduate school 28,113 32.2 1703 44.4 690 48.0 772 47.5
 (Missing) 8435   283   93   116  
Household income (×10,000 Japanese yen)
  < 200 4956 6.0 73 2.0 17 1.2 20 1.3
  ≥ 200, < 400 29,346 35.8 949 26.0 279 20.2 258 16.6
  ≥ 400, < 600 26,979 32.9 1319 36.1 480 34.7 521 33.5
  ≥ 600, < 800 12,554 15.3 747 20.4 318 23.0 391 25.1
  ≥ 800, < 1000 5012 6.1 328 9.0 161 11.6 204 13.1
  ≥ 1000 3224 3.9 240 6.6 128 9.3 161 10.4
 (Missing) 8435   283   93   116  
  1. ART assisted reproductive technologies, BMI body mass index, ICSI intracytoplasmic sperm injection. IQR interquartile range, IVF-ET in vitro fertilization and embryo transfer, OI ovulation induction
  2. Proportions were calculated excluding cases with missing data