Table 2.
Associations between women’s pregnancy duration and subsequent risk of stroke.
| Stroke cases |
Rate* | Age-adjusted† | Full model‡ | Risk difference§ (95% CI) |
||
|---|---|---|---|---|---|---|
| HR (95% CI) | HR (95% CI) | P | ||||
| 0-43 years after delivery | ||||||
| Preterm (<37 wks) | 4,243 | 106.2 | 1.57 (1.52, 1.62) | 1.42 (1.38, 1.47) | <0.001 | 35.7 (32.4, 39.0) |
| Extremely preterm (22-27 wks) | 198 | 128.6 | 2.01 (1.75, 2.31) | 1.77 (1.53, 2.03) | <0.001 | 58.1 (40.1, 76.0) |
| Very preterm (28-33 wks) | 1,150 | 123.9 | 1.82 (1.71, 1.93) | 1.61 (1.52, 1.71) | <0.001 | 53.4 (46.2, 60.6) |
| Late preterm (34-36 wks) | 2,895 | 99.4 | 1.46 (1.41, 1.52) | 1.34 (1.29, 1.40) | <0.001 | 28.9 (25.1, 32.6) |
| Early term (37-38 wks) | 9,082 | 81.2 | 1.20 (1.17, 1.23) | 1.16 (1.13, 1.19) | <0.001 | 10.7 (8.8, 12.6) |
| Full-term (39-41 wks) | 21,349 | 70.5 | Reference | Reference | Reference | |
| Post-term (≥42 wks) | 2,058 | 81.7 | 1.04 (1.00, 1.09) | 1.02 (0.97, 1.07) | 0.45 | 11.2 (7.5, 14.8) |
| Per additional week (trend) | 0.94 (0.94, 0.94) | 0.95 (0.95, 0.95) | <0.001 | |||
| <10 years after delivery | ||||||
| Preterm (<37 wks) | 451 | 31.8 | 1.85 (1.67, 2.05) | 1.61 (1.45, 1.79) | <0.001 | 15.2 (12.2, 18.2) |
| Extremely preterm (22-27 wks) | 37 | 63.8 | 3.57 (2.58, 4.94) | 2.81 (2.02, 3.91) | <0.001 | 47.2 (26.6, 67.7) |
| Very preterm (28-33 wks) | 144 | 44.2 | 2.54 (2.14, 3.00) | 2.07 (1.74, 2.46) | <0.001 | 27.6 (20.3, 34.9) |
| Late preterm (34-36 wks) | 270 | 26.1 | 1.53 (1.35, 1.74) | 1.38 (1.21, 1.57) | <0.001 | 9.5 (6.3, 12.7) |
| Early term (37-38 wks) | 867 | 21.2 | 1.24 (1.14, 1.34) | 1.15 (1.06, 1.24) | 0.001 | 4.6 (3.0, 6.2) |
| Full-term (39-41 wks) | 2,051 | 16.6 | Reference | Reference | Reference | |
| Post-term (≥42 wks) | 168 | 14.1 | 0.86 (0.73, 1.00) | 0.93 (0.79, 1.09) | 0.36 | −2.5 (−4.8, −0.3) |
| Per additional week (trend) | 0.91 (0.90, 0.92) | 0.93 (0.92, 0.94) | <0.001 | |||
| 10-19 years after delivery | ||||||
| Preterm (<37 wks) | 880 | 69.2 | 1.81 (1.68, 1.95) | 1.61 (1.50, 1.74) | <0.001 | 29.8 (25.1, 34.6) |
| Extremely preterm (22-27 wks) | 52 | 105.5 | 2.70 (2.05, 3.55) | 2.25 (1.71, 2.97) | <0.001 | 66.2 (37.4, 94.9) |
| Very preterm (28-33 wks) | 255 | 85.9 | 2.21 (1.95, 2.52) | 1.89 (1.66, 2.15) | <0.001 | 46.5 (35.9, 57.2) |
| Late preterm (34-36 wks) | 573 | 61.9 | 1.63 (1.49, 1.78) | 1.48 (1.36, 1.62) | <0.001 | 22.6 (17.3, 27.8) |
| Early term (37-38 wks) | 1,765 | 49.7 | 1.30 (1.22, 1.37) | 1.25 (1.18, 1.33) | <0.001 | 10.3 (7.6, 13.0) |
| Full-term (39-41 wks) | 3,398 | 39.4 | Reference | Reference | Reference | |
| Post-term (≥42 wks) | 260 | 45.3 | 1.02 (0.90, 1.15) | 0.98 (0.86, 1.11) | 0.71 | 5.9 (0.3, 11.6) |
| Per additional week (trend) | 0.92 (0.91, 0.93) | 0.93 (0.92, 0.94) | <0.001 | |||
| 20-29 years after delivery | ||||||
| Preterm (<37 wks) | 1,383 | 158.8 | 1.47 (1.39, 1.57) | 1.35 (1.28, 1.44) | <0.001 | 45.4 (36.7, 54.3) |
| Extremely preterm (22-27 wks) | 55 | 172.1 | 1.61 (1.24, 2.10) | 1.47 (1.13, 1.92) | 0.004 | 58.7 (13.2, 104.3) |
| Very preterm (28-33 wks) | 358 | 175.6 | 1.62 (1.46, 1.81) | 1.47 (1.32, 1.63) | <0.001 | 62.2 (43.9, 80.7) |
| Late preterm (34-36 wks) | 970 | 152.7 | 1.41 (1.32, 1.51) | 1.31 (1.23, 1.40) | <0.001 | 39.3 (29.4, 49.4) |
| Early term (37-38 wks) | 3,154 | 133.0 | 1.21 (1.16, 1.27) | 1.19 (1.14, 1.25) | <0.001 | 19.6 (14.3, 25.1) |
| Full-term (39-41 wks) | 6,662 | 113.4 | Reference | Reference | Reference | |
| Post-term (≥42 wks) | 625 | 145.2 | 1.15 (1.06, 1.25) | 1.08 (0.99, 1.17) | 0.09 | 31.8 (20.1, 43.5) |
| Per additional week (trend) | 0.95 (0.94, 0.96) | 0.96 (0.95, 0.96) | <0.001 | |||
| 30-43 years after delivery | ||||||
| Preterm (<37 wks) | 1,529 | 351.6 | 1.42 (1.34, 1.49) | 1.35 (1.27, 1.42) | <0.001 | 82.5 (64.0, 100.9) |
| Extremely preterm (22-27 wks) | 54 | 366.5 | 1.50 (1.15, 1.96) | 1.41 (1.08, 1.84) | 0.01 | 97.4 (−0.5, 195.3) |
| Very preterm (28-33 wks) | 393 | 385.7 | 1.56 (1.41, 1.73) | 1.48 (1.34, 1.64) | <0.001 | 116.6 (78.1, 155.2) |
| Late preterm (34-36 wks) | 1,082 | 340.0 | 1.36 (1.28, 1.45) | 1.30 (1.22, 1.38) | <0.001 | 70.9 (49.9, 91.9) |
| Early term (37-38 wks) | 3,296 | 280.4 | 1.10 (1.06, 1.15) | 1.09 (1.05, 1.14) | <0.001 | 11.3 (0.3, 22.4) |
| Full-term (39-41 wks) | 9,238 | 269.1 | Reference | Reference | Reference | |
| Post-term (≥42 wks) | 1,005 | 310.5 | 1.05 (0.99, 1.13) | 1.01 (0.94, 1.08) | 0.79 | 41.4 (21.4, 61.4) |
| Per additional week (trend) | 0.96 (0.95, 0.97) | 0.96 (0.95, 0.97) | <0.001 | |||
*
Stroke incidence rate per 100,000 person-years.
†
Adjusted for maternal age (as Cox model time scale).
‡
Further adjusted for year of delivery, parity, education, employment, income, region of origin, BMI, smoking, preeclampsia, other hypertensive disorders, and diabetes prior to delivery.
§
Incidence rate difference per 100,000 person-years.