Baseline age, family history of stroke and weekly physical activity and risk of subsequent singleton stillbirth delivery: Cohort Norway (CONOR) and Medical Birth Registry of Norway
| Total births (n=13 497)* | Births to women with normal BMI (18.5–24.9 kg/m2) (n=9131) | |||||||
| Characteristics: | N | Cases | Unadjusted IRR (95% CI) | Adjusted† IRR (95% CI) | N | Cases | Unadjusted IRR (95% CI) | Adjusted† IRR (95% CI) |
| Baseline age (years) | ||||||||
| <25 | 3770 | 9 | 1.0 | 1.0 | 2588 | 4 | 1.0 | 1.0 |
| 25–30 | 4108 | 16 | 1.63 (0.72 to 3.68) | 1.53 (0.68 to 3.44) | 2735 | 8 | 1.89 (0.57 to 6.25) | 1.54 (0.43 to 5.49) |
| 31–35 | 5005 | 23 | 1.92 (0.89 to 4.14) | 1.76 (0.83 to 3.74) | 3446 | 12 | 2.25 (0.73 to 6.96) | 1.70 (0.53 to 5.48) |
| >35 | 614 | 6 | 4.09 (1.47 to 11.42) | 3.56 (1.27 to 10.02) | 362 | 4 | 7.15 (1.81 to 28.27) | 4.57 (1.02 to 20.55) |
| Light physical activity | ||||||||
| <3 hours/week | 6520 | 36 | 1.0 | 1.0 | 4260 | 19 | 1.0 | 1.0 |
| 3+ hours/week | 6171 | 18 | 0.53 (0.30 to 0.93) | 0.53 (0.32 to 0.93) | 4332 | 9 | 0.47 (0.21 to 1.03) | 0.47 (0.21 to 1.04) |
| Vigorous physical activity | ||||||||
| <1 hour/week | 6572 | 20 | 1.0 | 1.0 | 4253 | 7 | 1.0 | 1.0 |
| 1–2 hours/week | 3938 | 17 | 1.42 (0.75 to 2.70) | 1.48 (0.78 to 2.84) | 2746 | 10 | 2.21 (0.84 to 5.80) | 2.33 (0.89 to 6.12) |
| 3+ hours/week | 2125 | 14 | 2.16 (1.09 to 4.25) | 2.46 (1.23 to 4.90) | 1579 | 10 | 3.85 (1.47 to 10.04) | 4.50 (1.72 to 11.79) |
| BMI (kg/m2) groups | ||||||||
| Low/normal<25 | 9420 | 29 | 1.0 | 1.0 | ||||
| Overweight (25–29.9) | 3113 | 12 | 1.25 (0.64 to 2.45) | 1.22 (0.62 to 2.39) | ||||
| Obese (> 30) | 918 | 13 | 4.61 (2.42 to 8.79) | 4.35 (2.25 to 8.41) | ||||
| Family history of stroke | ||||||||
| No | 12 885 | 48 | 1.0 | 1.0 | 8792 | 24 | 1.0 | 1.0 |
| Yes | 564 | 6 | 2.87 (1.24 to 6.62) | 2.53 (1.06 to 6.01) | 339 | 4 | 4.32 (1.52 to 12.27) | 3.81 (1.31 to 11.07) |
| Family history of myocardial infarction | ||||||||
| No | 12 360 | 51 | 1.0 | 1.0 | 8407 | 27 | 1.0 | 1.0 |
| Yes | 1137 | 3 | 0.64 (0.20 to 2.04) | 0.57 (0.18 to 1.83) | 724 | 1 | 0.43 (0.06 to 3.16) | 0.37 (0.05 to 2.74) |
| Quartiles diastolic BP (mm Hg) | ||||||||
| Q1 (<62.1) | 2858 | 9 | 1.0 | 1.0 | 2106 | 4 | 1.0 | 1.0 |
| Q2 (62.1–67.5) | 3299 | 11 | 1.06 (0.44 to 2.55) | 1.05 (0.43 to 2.53) | 2322 | 6 | 1.36 (0.39 to 4.80) | 1.36 (0. 38 to 4.82) |
| Q3 (68.0–73.5) | 3536 | 10 | 0.90 (0.37 to 2.20) | 0.90 (0.37 to 2.22) | 2390 | 5 | 1.10 (0.30 to 4.08) | 1.13 (0.30 to 4.18) |
| Q4 (>73.5) | 3752 | 24 | 2.03 (0.95 to 4.35) | 2.02 (0.94 to 4.31) | 2273 | 13 | 3.01 (0.99 to 9.19) | 3.03 (0.99 to 9.24) |
| Quartiles systolic BP (mm Hg) | ||||||||
| Q1 (<79.5) | 3089 | 12 | 1.0 | 1.0 | 2355 | 5 | 1.0 | 1.0 |
| Q2 (111–117) | 3151 | 10 | 0.82 (0.35 to 1.88) | 0.84 (0.37 to 1.94) | 2273 | 5 | 1.03 (0.30 to 3.56) | 1.08 (0.32 to 3.72) |
| Q3 (117.5–125) | 3638 | 17 | 1.20 (0.58 to 2.50) | 1.26 (0.60 to 2.65) | 2457 | 10 | 1.92 (0.66 to 5.59) | 2.09 (0.70 to 6.21) |
| Q4 (>135.0) | 3567 | 15 | 1.08 (0.51 to 2.30) | 1.17 (0.55 to 2.51) | 2006 | 8 | 1.88 (0.62 to 5.71) | 2.16 (0.69 to 6.78) |
*13 497 births to 8478 women, representing 1.59 births/woman; 54 stillbirths represent 54 unique women. Exclusions: births<22 weeks and mother pregnant during or delivered <1 year prior to CONOR participation.
†Adjusted for CONOR baseline age (years) and length of follow-up in Poisson regression entering mothers’ pseudo-ID as cluster variable.