Table 1.

Adjusted IRRs for associations between gestational factors and subsequent risk of colorectal cancer in the mother (1973–2009)a

Subsequent colorectal cancer
No (N = 3,577,984 births among 1,831,191 mothers)Yes (N = 12,539 births among 7,318 mothers)IRR (95% CI)P
Offspring variables
 Sex
  Female1,739,064 (48.6)6,018 (48.0)1.00
  Male1,838,920 (51.4)6,521 (52.0)1.02 (0.99–1.06)0.26
 Fetal growth (SD)
  <−1527,227 (14.7)1,998 (15.9)1.04 (0.99–1.10)0.14
  −1 to <12,519,511 (70.4)8,530 (68.0)1.00
  ≥1531,246 (14.9)2,011 (16.0)1.17 (1.09–1.27)<0.001
  Per SD (trend test)1.05 (1.03–1.07)<0.001
 Birth weight (g)
  <2,500151,673 (4.2)553 (4.4)0.92 (0.82–1.04)0.19
  2,500—3,9992,783,705 (77.8)9,618 (76.7)1.00
  ≥4,000642,606 (18.0)2,368 (18.9)1.08 (1.03–1.14)0.004
  Per 1,000 g (trend test)1.12 (1.07–1.17)<0.001
 Birth length (cm)
  <48381,873 (10.7)1,266 (10.1)0.93 (0.87–1.01)0.07
  48–522,617,718 (73.2)8,981 (71.6)1.00
  ≥53578,393 (16.2)2,292 (18.3)1.11 (1.06–1.17)<0.001
  Per cm (trend test)1.02 (1.01–1.03)<0.001
 Gestational age at birth (wks)
  <3454,691 (1.5)199 (1.6)1.10 (0.94–1.29)0.23
  34–36154,202 (4.3)578 (4.6)1.07 (0.97–1.18)0.15
  37–413,070,834 (85.8)10,487 (83.6)1.00
  ≥42298,257 (8.3)1,275 (10.2)1.08 (1.01–1.15)0.02
  Per week (trend test)1.00 (0.99–1.02)0.48
 Multiple gestation
  Singleton3,492,817 (97.6)12,229 (97.5)1.00
  Twin or higher order85,167 (2.4)310 (2.5)1.22 (1.04–1.44)0.02
Maternal variables
 Age, y
  <25765,425 (21.4)1,762 (14.0)0.60 (0.56–0.64)<0.001
  25–291,257,777 (35.2)3,871 (30.9)1.00
  30–341,035,956 (28.9)3,939 (31.4)1.61 (1.54–1.68)<0.001
  ≥35518,826 (14.5)2,967 (23.7)2.95 (2.78–3.13)<0.001
  Per higher category (trend test)1.69 (1.65–1.74)<0.001
 Parity
  11,503,979 (42.0)4,246 (33.9)1.00
  21,302,161 (36.4)4,710 (37.6)0.97 (0.94–0.99)0.03
  3541,966 (15.1)2,383 (19.0)0.92 (0.87–0.97)0.001
  ≥4229,878 (6.4)1,200 (9.6)0.88 (0.81–0.97)0.007
  Per higher category (trend test)0.96 (0.93–0.98)0.001
 Body mass index
  <18.583,168 (2.3)184 (1.5)1.00 (0.85–1.19)0.96
  18.5–252,887,403 (80.7)11,150 (88.9)1.00
  25–30459,649 (12.9)1,031 (8.2)1.01 (0.94–1.09)0.81
  >30147,764 (4.1)174 (1.4)1.14 (0.95–1.37)0.17
  Per 1 unit higher (trend test)1.01 (1.00–1.02)0.04
 Diabetes
  Yes15,965 (0.4)55 (0.4)1.00
  No3,562,019 (99.6)12,484 (99.6)1.04 (0.74–1.47)0.81
 Education, y
  ≤9705,400 (19.7)3,239 (25.8)1.00
  10–111,201,348 (33.6)4,561 (36.4)1.05 (0.99–1.13)0.13
  12–141,092,093 (30.5)2,880 (23.0)0.97 (0.90–1.04)0.40
  ≥15579,143 (16.2)1,859 (14.8)0.97 (0.89–1.06)0.48
  Per higher category (trend test)0.98 (0.95–1.01)0.15
 Marital status
  Married/cohabiting2,874,398 (80.3)9,187 (73.3)1.00
  Never married350,693 (9.8)1,912 (15.2)1.05 (0.99–1.11)0.14
  Divorced/widowed352,893 (9.9)1,440 (11.5)1.07 (1.01–1.14)0.03
 Country of birth
  Sweden2,858,477 (79.9)10,280 (82.0)1.00
  Other Western countries418,264 (11.7)1,756 (14.0)1.05 (0.97–1.13)0.19
  Other non-Western countries301,243 (8.4)503 (4.0)1.05 (0.91–1.21)0.52
  • aThe model included maternal age, date of delivery, parity, diabetes, body mass index, and education level; and fetal growth, gestational age at birth, and multiple gestation of the offspring. Birth weight and length of the offspring were examined in separate models as alternatives to the standardized fetal growth variable. The reference category for all variables is indicated by an IRR of 1.00.