Table 1

Characteristics of the children included in the cohort, and that of their mothers, contrasted by standardised differences

CharacteristicMale children
(n=1 609 644)
Female children
(n=1 530 054)
Standardised difference
Of the mother at the birth
Mean (SD) age, years29.6 (5.4)29.6 (5.4)0.00
Median (IQR) number of previous live births1.0 (0.0–1.0)1.0 (0.0–1.0)0.00
 No previous live birth790 081 (49.1)751 990 (49.1)0.00
 Any previous live birth564 351 (35.1)536 816 (35.1)0.00
 Missing information on previous live birth3782 (0.2)3624 (0.2)0.00
Maternal world region of origin
 Canada/long-term resident/missing*1 257 056 (78.1)1 196 246 (78.2)0.00
 Sub-Saharan Africa26 199 (1.7)27 224 (1.7)0.00
 Caribbean21 602 (1.4)22 439 (1.4)0.00
 Middle East/North Africa33 720 (2.1)32 508 (2.1)0.00
 South Asia98 887 (6.1)93 168 (6.1)0.00
 Hispanic America28 318 (1.8)27 123 (1.8)0.00
 Western Nations/Europe59 502 (3.7)56 185 (3.7)0.00
 East Asia/Pacific82 410 (5.1)76 941 (5.0)0.00
Of the child
Mean (SD) birth weight, g3440 (585)3322 (555)0.21
Mean (SD) gestational age at birth, weeks38.0 (1.8)38.0 (1.8)0.02
 <283734 (0.2)3418 (0.2)0.00
 28–3110 089 (0.6)8377 (0.6)0.01
 32–36109 153 (6.8)92 890 (6.1)0.03
 37+1 486 668 (92.4)1 425 369 (93.2)0.03
Multiple birth46 496 (2.9)45 786 (3.0)0.01
Any congenital or chromosomal anomaly diagnosed before age 1 year131 134 (8.2)96 264 (6.3)0.07
Income quintile (Q) at age 1 year
 Q1350 902 (21.8)334 349 (21.9)0.00
 Q2319 496 (19.9)303 669 (19.9)0.00
 Q3324 957 (20.2)309 245 (20.2)0.00
 Q4331 985 (20.6)314 879 (20.6)0.00
 Q5273 672 (17.0)259 521 (17.0)0.00
 Missing8632 (0.54)8391 (0.6)0.00
Residence at age 1 year
 Urban1 429 301 (88.8)1 358 953 (88.8)0.00
 Rural178 576 (11.1)169 416 (11.1)0.00
 Missing1767 (0.1)1685 (0.1)0.00
Median (IQR) age at end of study follow-up, year13.7 (7.7–20.4)13.7 (7.7–20.4)0.00
  • All data are presented as a number (%), unless otherwise indicated.

  • *Includes 170 women with missing information on immigrant country of origin.