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Table 1 Mother’s sociodemographic characteristics, prenatal care assistance, type of delivery and live birth at second pregnancy by preterm birth status at the first birth, 2001–2015 (n=1,764,025)

From: Differences in risk factors for incident and recurrent preterm birth: a population-based linkage of 3.5 million births from the CIDACS birth cohort

Second pregnancy variables Total population
(n = 1,764,025)
First pregnancy
Term
(n = 1,634,253)
Preterm
(n = 129,772)
n % n % n %
Urban/rural area of residence
 Urban 1,303,734 77.07 1205,124 76.88 98,604 79.46
 Rural 387,896 29.93 362,396 23.12 25,493 20.54
 Missing 72,395 4.10     
Household overcrowding
 No 1,015,851 62.24 946,688 62.60 69,163 57.67
 Yes 616,397 37.76 565,627 37.40 50,770 42.33
 Missing 131,777 7.47     
Maternal race/ethnicity
 White 541,650 33.66 501,731 33.44 39,919 33.55
 Black/mixed-race 1,067,316 65,90 989,219 65.63 78,097 65.63
 Indigenous 10,552 0.65 9,564 0.64 988 0.83
 Missing 144,507 8.19     
Maternal education
 < 8 years of study 638,901 36.78 592,159 36.80 46,742 36.56
 8 to 11 years of study 996,380 57.36 921,907 57.29 74,473 58.24
 ≥ 12 years of study 101,867 5.86 95,220 5.92 6647 5.20
 Missing 26,877 1.52     
Marital status
 Married, civil union 789,961 45.32 734,464 45.48 55,494 43.28
 Single, divorced, widow 953,095 54.68 880,365 54.52 72,729 56.72
 Missing 20.969 1.19     
Number of prenatal visits
 None 30,255 1.73 27,210 1.68 3045 2.37
 1 to 3 visits 154,340 8.81 139,556 8.60 14,784 11.50
 ≥ 4 visits 1,566,330 89.46 1,455,636 89.72 110,694 86.13
 Missing 13,100 0.74     
Interbirth interval
 <12 months 20,090 1.14 16,544 1.01 3,546 2.73
 12 to 23 months 297,459 16.86 266,622 16.31 30,837 23.76
 ≥24 months 1,446,476 82.00 1351,087 82.67 95,389 73.50
 Missing 0 0.0     
Maternal age at birth
 14 to 19 years 325,3112 18.44 290,336 17.77 34,976 26.95
 20 to 34 years 1,377,140 78.07 1,286,293 78.71 90,847 70.01
 35 to 49 years 61,573 3.49 57,624 3.53 3949 3.04
 Missing 0 0.0     
Type of delivery
 Vaginal 988,727 56.10 910,214 55.75 78,513 60.53
 Cesarean 773,562 43.90 722,428 44.25 51,134 39.44
 Missing 1,736 0.10     
Newborn sex
 Female 859,905 48.75 796,213 48.72 63,692 49.08
 Male 903,963 51.25 837,891 51.28 66,072 50.92
 Missing 157 0.01