| Characteristic | No. of pregnancies n = 264 737 | Rate ratio (95% CI) | |
|---|---|---|---|
| Unadjusted | Adjusted* | ||
| Maternal age at delivery/abortion, yr | |||
| ≤ 20 | 19 622 | 0.55 (0.54–0.56) | 0.81 (0.80–0.83) |
| 21–34 | 197 976 | 0.85 (0.84–0.86) | 0.94 (0.93–0.95) |
| ≥ 35 | 47 139 | 1.00 (ref) | 1.00 (ref) |
| Maternal age at first delivery, yr | |||
| ≤ 20 | 38 411 | 0.54 (0.53–0.55) | 0.85 (0.84–0.86) |
| 21–34 | 197 873 | 0.83 (0.82–0.84) | 1.00 (0.99–1.01) |
| ≥ 35 | 28 453 | 1.00 (ref) | 1.00 (ref) |
| Parity (previous deliveries) | |||
| 0 | 134 061 | 1.00 (ref) | 1.00 (ref) |
| 1 | 87 628 | 1.00 (0.99–1.01) | 0.97 (0.96–0.97) |
| 2 | 30 525 | 0.88 (0.87–0.89) | 0.89 (0.89–0.90) |
| ≥□3 | 12 523 | 0.66 (0.65–0.68) | 0.76 (0.75–0.78) |
| Previous delivery of stillborn child | 2 163 | 1.07 (1.04–1.10) | 1.04 (1.03–1.06) |
| Previous abortion in past 5 yr | 39 047 | 1.01 (1.00–1.02) | 1.00 (0.99–1.01) |
| Previous delivery of child with congenital anomaly | 9 229 | 0.92 (0.90–0.93) | 1.00 (0.99–1.02) |
| Immigration status | |||
| Canadian resident | 193 187 | 1.00 (ref) | 1.00 (ref) |
| Immigrant | |||
| Landed ≥ 5 yr ago | 31 308 | 1.33 (1.32–1.34) | 1.15 (1.15–1.16) |
| Landed < 5 yr ago | 31 274 | 1.27 (1.26–1.28) | 1.15 (1.14–1.16) |
| Refugee | |||
| Landed ≥ 5 yr ago | 5 423 | 1.17 (1.15–1.20) | 1.08 (1.06–1.10) |
| Landed < 5 yr ago | 3 545 | 1.17 (1.14–1.20) | 1.10 (1.08–1.12) |
| Neighbourhood income quintile | |||
| 1 (lowest) | 60 660 | 0.90 (0.89–0.91) | 0.95 (0.94–0.96) |
| 2 | 53 750 | 0.94 (0.93–0.95) | 0.97 (0.96–0.98) |
| 3 | 53 273 | 0.96 (0.95–0.97) | 0.97 (0.96–0.98) |
| 4 | 53 604 | 0.99 (0.98–1.00) | 0.98 (0.98–0.99) |
| 5 (highest) | 41 928 | 1.00 (ref) | 1.00 (ref) |
| Missing data | 1 522 | 0.59 (0.55–0.63) | 0.97 (0.93–1.01) |
| Rurality index score† | |||
| 0–9 (major urban) | 199 919 | 1.00 (ref) | 1.00 (ref) |
| 10–39 (non-major urban) | 45 320 | 0.69 (0.68–0.70) | 0.76 (0.75–0.76) |
| ≥ 40 (rural) | 16 697 | 0.57 (0.56–0.58) | 0.67 (0.66–0.68) |
| Missing data | 2 801 | 0.42 (0.40–0.45) | 0.63 (0.60–0.67) |
| First-trimester health care provider | |||
| Prenatal obstetrician | 84 553 | 1.00 (ref) | 1.00 (ref) |
| Prenatal GP/FP | 118 520 | 0.84 (0.83–0.85) | 0.91 (0.90–0.92) |
| Primary GP/FP | 36 684 | 0.66 (0.65–0.66) | 0.72 (0.71–0.73) |
| Other physician | 7 707 | 0.51 (0.49–0.52) | 0.65 (0.64–0.67) |
| Midwife only | 2 562 | 0.35 (0.33–0.37) | 0.40 (0.38–0.43) |
| No care | 14 711 | 0.14 (0.13–0.15) | 0.15 (0.14–0.16) |
Note: CI = confidence interval, GP/FP = general practitioner/family physician, ref = reference group. *Adjusted for other factors in the table. †Measured with the Rurality Index for Ontario. (41)