Table 1.
Selected characteristics of the study population, Ontario, Canada (2006–2012).
| Characteristics | Total (%) | Preterm birth (%) | Term low birth weight (%) |
|---|---|---|---|
| Sex | |||
| Male | 100,585 (51.3) | 8,401 (54.6) | 1,646 (40.9) |
| Female | 95,586 (48.7) | 6,977 (45.4) | 2,377 (59.1) |
| Maternal age | |||
| 7,792 (4.0) | 649 (4.2) | 201 (5.0) | |
| 20–34 | 148,042 (75.5) | 10,982 (71.4) | 2,938 (73.0) |
| 40,337 (20.6) | 3,747 (24.4) | 884 (22.0) | |
| Parity | |||
| 0 | 90,541 (45.2) | 7,148 (46.5) | 2,080 (51.7) |
| 1 | 67,504 (34.4) | 4,912 (31.9) | 1,190 (29.6) |
| 38,092 (19.4) | 3,313 (21.5) | 751 (18.7) | |
| Missing | 34 (0.02) | 5 (0.03) | 2 (0.05) |
| Smoking during pregnancy | |||
| Yes | 15,890 (8.1) | 1,276 (8.3) | 342 (8.5) |
| No | 158,898 (81.0) | 12,425 (80.8) | 3,247 (80.7) |
| Missing | 21,383 (10.9) | 1,676 (10.9) | 434 (10.8) |
| Previous caesarean section | |||
| Yes | 26,483 (13.5) | 2,153 (14.0) | 539 (13.4) |
| No | 167,726 (85.5) | 13,071 (85.0) | 3,484 (86.6) |
| Missing | 1,962 (1.0) | 154 (1.0) | 44 (1.1) |
| Maternal preexisting asthma | |||
| Yes | 11,770 (6.0) | 938 (6.1) | 233 (5.8) |
| No | 184,400 (94.0) | 14,440 (93.9) | (94.2) |
| Maternal preexisting hypertension | |||
| Yes | 4,708 (2.4) | 384 (2.5) | 105 (2.6) |
| No | 176,554 (90.0) | 13,825 (89.9) | 3613 (89.8) |
| Missing | 14,909 (7.6) | 1,169 (7.6) | 306 (7.6) |
| Gestational hypertension | |||
| Yes | 12,555 (6.4) | 984 (6.4) | 237 (5.9) |
| No | 170,669 (87.0) | 13,379 (87.0) | 3,520 (87.5) |
| Missing | 12,947 (6.6) | 1,015 (6.6) | 266 (6.6) |
| Maternal preexisting heart disease | |||
| Yes | 1,177 (0.6) | 77 (0.5) | 12 (0.3) |
| No | 180,085 (91.8) | 14,132 (91.9) | 3,705 (92.1) |
| Missing | 14,909 (7.6) | 1,169 (7.6) | 306 (7.6) |
| Maternal preexisting type 1 or type 2 diabetes | |||
| Yes | 6,278 (3.2) | 523 (3.4) | 129 (3.2) |
| No | 174,985 (89.2) | 13,748 (89.4) | 3,589 (89.2) |
| Missing | 14,909 (7.6) | 1,169 (7.6) | 306 (7.6) |
| Gestational diabetes | |||
| Yes | 15,498 (7.9) | 1,276 (8.3) | 323 (8.2) |
| No | 180,674 (92.1) | 14,102 (91.7) | 3,693 (91.8) |
| Missing | 12,947 (6.6) | 1,015 (6.6) | 266 (6.6) |
| Dissemination-area median family income | |||
| Quartile 1 | 49,368 (25.2) | 4,034 (26.2) | 1,150 (28.6) |
| Quartile 2 | 48,911 (24.9) | 3,878 (25.2) | 1,058 (26.3) |
| Quartile 3 | 49,312 (25.1) | 3,801 (24.7) | 973 (24.2) |
| Quartile 4 | 47,424 (24.2) | 3,568 (23.2) | 820 (20.4) |
| Missing | 1,156 (0.6) | 97 (0.6) | 22 (0.6) |
| Dissemination-area percent of females who completed postsecondary education | |||
| Quartile 1 | 48,420 (24.7) | 3,953 (25.7) | 1,030 (25.6) |
| Quartile 2 | 50,658 (25.8) | 4,036 (26.3) | 1,083 (26.9) |
| Quartile 3 | 47,236 (24.1) | 3,741 (24.3) | 946 (23.5) |
| Quartile 4 | 48,701 (24.8) | 3,551 (23.1) | 942 (23.4) |
| Missing | 1,156 (0.6) | 97 (0.6) | 22 (0.6) |
| Dissemination-area percent of visible minority | |||
| Quartile 1 | 46,287 (23.6) | 3,633 (23.6) | 781 (19.4) |
| Quartile 2 | 48,421 (24.7) | 3,826 (24.9) | 875 (21.8) |
| Quartile 3 | 49,284 (25.1) | 3,864 (25.1) | 1,017 (25.3) |
| Quartile 4 | 50,843 (25.9) | 3,938 (25.6) | 1,326 (33.0) |
| Missing | 1,336 (0.7) | 117 (0.8) | 24 (0.6) |
| Total | 196,171 (100) | 15,378 (100) | 4,023 (100) |