Second pregnancy variables | Incident preterm birth | Recurrent preterm birth | Pdifference b | ||||
---|---|---|---|---|---|---|---|
n (%) | ORa | 95% CI | n (%) | ORa | 95% CI | ||
Urban/rural area of residence | |||||||
Urban | 86,747 (7.20) | Ref | Ref | 18,003 (18.26) | Ref | Ref | 0.96 |
Rural | 24,279 (6.70) | 0.90 | 0.89–0.92 | 4395 (17.24) | 0.90 | 0.87–0.94 | |
Household overcrowding | |||||||
No | 63,415 (6.70) | Ref | Ref | 12,155 (17.57) | Ref | Ref | <0.00 |
Yes | 43,080 (7.62) | 1.09 | 1.07–1.10 | 9469 (18.65) | 1.01 | 0.98–1.04 | |
Maternal race/ethnicity | |||||||
White | 33,781 (6.73) | Ref | Ref | 7237 (18.13) | Ref | Ref | <0.00 |
Black/Mixed-race | 71,741 (7.25) | 1.04 | 1.03–1.06 | 14,003 (17.93) | 0.95 | 0.92–0.98 | |
Indigenous | 981 (10.26) | 1.34 | 1.24–1.44 | 215 (21.76) | 1.14 | 0.96–1.35 | |
Maternal education | |||||||
≥ 12 years of study | 5659 (5.94) | Ref | Ref | 1,060 (15.95) | Ref | Ref | 0.27 |
8 to 11 years of study | 66,183 (7.18) | 1.21 | 1.17–1.25 | 13,523 (18.16) | 1.13 | 1.05–1.22 | |
<8 years of study | 41,944 (7.08) 41,944 (7.08 | 1.12 | 1.09–1.16 | 8430 (18.04) | 1.06 | 0.98–1.14 | |
Marital status | |||||||
Married, civil union | 53,922 (7.34) | Ref | Ref | 10,132 (18.26) | Ref | Ref | <0.00 |
Single, divorced, widow | 60,422 (6.86) | 0.85 | 0.84–0.86 | 12,948 (17.80) | 0.90 | 0.87–0.93 | |
Number of prenatal visits | |||||||
≥ 4 visits | 90,941 (6.25) | Ref | Ref | 17,608 (15.91) | Ref | Ref | <0.00 |
1 to 3 visits | 19,606 (14.05) | 2.44 | 2.40–2.49 | 4531 (30.65) | 2.24 | 2.14–2.33 | |
None | 3967 (14.58) | 2.56 | 2.47–2.66 | 902 (29.62) | 2.16 | 1.98–2.36 | |
Interbirth interval | |||||||
≥24 months | 91,934 (6.80) | Ref | Ref | 15,703 (16.46) | Ref | Ref | <0.00 |
12 to 23 months | 21,499 (8.06) | 1.04 | 1.02–1.06 | 6366 (20.64) | 1.22 | 1.17–1.26 | |
<12 months | 2344 (14.17) | 1.89 | 1.80–1.98 | 1293 (36.46) | 2.58 | 2.38–2.79 | |
Maternal age at birth | |||||||
20 to 34 years | 86,081 (6.69) | Ref | Ref | 15,415 (16.97) | Ref | Ref | <0.00 |
14 to 19 years | 24,548 (8.46) | 1.16 | 1.14–1.18 | 7080 (20.24) | 1.02 | 0.98–1.06 | |
35 to 49 years | 5148 (8.93) | 1.42 | 1.38–1.47 | 867 (21.95) | 1.45 | 1.33–1.58 | |
Type of delivery | |||||||
Vaginal | 64,128 (7.05) | Ref | Ref | 14,656 (18.67) | Ref | Ref | <0.00 |
Cesarean | 51,494 (7.13) | 1.09 | 1.08–1.11 | 8679 (16.97) | 0.96 | 0.92–0.99 | |
Newborn sex | |||||||
Female | 54,808 (6.88) | Ref | Ref | 11,078 (17.39) | Ref | Ref | 0.25 |
Male | 60,956 (7.27) | 1.06 | 1.05–1.07 | 12,283 (18.59) | 1.08 | 1.05–1.12 |