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Table 1 Characteristics of the study subjects

From: Association between surgical procedures under general anesthesia in infancy and developmental outcomes at 1 year: the Japan Environment and Children’s Study

 

All subjects (N = 64,141)

Sex of infants

 Boy

32,727 (51.0%)

 Girl

31,414 (49.0%)

Gestational age at birth, mean [SD], weeks

39.1 [1.1]

Birth weight, g

 < 2000

115 (0.2%)

 2000–2499

3268 (5.1%)

 2500–3999

60,186 (93.8%)

 ≥ 4000

558 (0.9%)

 Missing

14 (0.0%)

Apgar score at 5 min

 0–3

68 (0.1%)

 4–6

127 (0.2%)

 ≥ 7

60,890 (94.9%)

 Missing

3056 (4.8%)

Delivery method

 Vaginal

52,974 (82.6%)

 Caesarean section

11,022 (17.2%)

 Missing

145 (0.2%)

Maternal age at birth, mean [SD], years

31.3 [4.9]

 < 20

368 (0.6%)

 20–24

5002 (7.8%)

 25–34

41,294 (64.4%)

 35–39

14,617 (22.8%)

 ≥ 40

2857 (4.5%)

 Missing

3 (0.0%)

Number of siblings

 

 0

29,565 (46.1%)

 1

23,509 (36.7%)

 ≥ 2

10,756 (16.8%)

 Missing

311 (0.5%)

Number of surgical procedures under general anesthesia

 0

63,234 (98.6%)

 1

746 (1.2%)

 2

90 (0.1%)

 ≥ 3

71 (0.1%)

Congenital disease at age 1

 Head and face

 

  Yes

217 (0.3%)

  No

63,924 (99.7%)

 Eye and ear

  Yes

506 (0.8%)

  No

63,635 (99.2%)

 Spinal cord

  Yes

52 (0.1%)

  No

64,089 (99.9%)

 Heart

  Yes

865 (1.3%)

  No

63,276 (98.7%)

 Chest (without heart) and digestive organs (abdomen)

  Yes

339 (0.5%)

  No

63,802 (99.5%)

 Skin

  Yes

1378 (2.1%)

  No

62,763 (97.9%)

 Upper and lower limb/muscle/bone/joint

  Yes

412 (0.6%)

  No

63,729 (99.4%)

 Kidney/urogenital apparatus

  Yes

562 (0.9%)

  No

63,579 (99.1%)

 Endocrine system/hormone

  Yes

130 (0.2%)

  No

64,011 (99.8%)

 Metabolism

  Yes

20 (0.0%)

  No

64,121 (100.0%)

 Others

  Yes

229 (0.4%)

  No

63,912 (99.6%)

  1. Data are n (%) unless otherwise specified
  2. SD standard deviation