Table 1.

Birth and demographic characteristics of subjects in a study of leukemia risk among California children diagnosed between 1988 and 2007

Controls (n = 68,040)ALL cases (n = 3,402)
N (%)aN (%)a
Sex
 Male34,788 (51.1)1,921 (56.5)
 Female33,252 (48.9)1,481 (43.5)
Gestational age, wks
 ≤366,557 (10.2)332 (10.3)
 37–4255,191 (85.6)2,761 (85.6)
 43+2,692 (4.2)131 (4.1)
 Missing3,600178
Age of mother, y
 <207,466 (11.0)325 (9.6)
 20–2935,669 (52.4)1,705 (50.1)
 30–3415,674 (23.0)826 (24.3)
 35+9,222 (13.6)546 (16.0)
 Missing90
Mother's educationb
 ≤8 years8,166 (13.8)410 (13.8)
 Some high school (9–11 y)10,673 (18.0)511 (17.2)
 High school diploma (12 y)17,519 (29.6)895 (30.2)
 Some college (13–15 y)11,616 (19.6)553 (18.7)
 College diploma or higher (16+y)11,203 (18.9)596 (20.1)
 Missing8,863437
Mother's race
 White24,695 (36.5)1,233 (36.4)
 Hispanic30,526 (45.1)1,680 (49.6)
 Other12,439 (18.4)472 (13.9)
 Missing38017
Season of birth
 Spring16,713 (24.6)864 (25.4)
 Summer17,500 (25.7)924 (27.2)
 Fall17,400 (25.6)807 (23.7)
 Winter16,427 (24.1)807 (23.7)
Parity
 First birth26,803 (39.4)1,288 (37.9)
 Second or third birth32,651 (48.0)1,669 (49.1)
 Fourth or subsequent birth8,549 (12.6)443 (13.0)
 Missing372
Payment source for prenatal careb
 Private insurance30,074 (50.7)1,656 (55.6)
 Other29,238 (49.3)1,321 (44.4)
 Missing8728425
Age at diagnosis (cases only), y
 0196 (5.8)
 1499 (14.7)
 2882 (25.9)
 3820 (24.1)
 4623 (18.3)
 5382 (11.2)
  • aPercentage of nonmissing.

  • bMother's education and the payment source for prenatal care began to be collected on California birth certificates in 1989. Starting that year, 1.5% of birth certificates were missing information on maternal education, and 1.3% were missing information on payment.