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Table 1 Sociodemographic characteristics of women in the study (i)

From: Pregnancy, prison and perinatal outcomes in New South Wales, Australia: a retrospective cohort study using linked health data

   Pregnancy in prison (ii)
   Birth in prison Birth out of prison All pregnancy in prison (ii) Prison controls (iii) Community controls (iv)
   n % n % n % n % P value (v) n % P value (v)
Maternal age (years)              
  Mean      26.5 27.2   30.0 <0.001
  Less than 20 6 6.1 11 5.4 17 5.6 108 8.7 0.0032 1540 3.9 <0.0001
  20–24 34 34.3 93 45.8 127 42.1 382 30.9 6045 15.4
  25–29 32 32.3 52 25.6 84 27.8 373 30.1 11472 29.1
  30–34 20 20.2 34 16.7 54 17.9 252 20.4 12798 32.5
  35 and over 7 7.1 13 6.4 20 6.6 119 9.6 7414 18.8
Parity             
  None 30 30.3 57 28.1 87 28.8 410 33.1 0.5511 22061 56.0 <0.0001
  One 29 29.3 52 25.6 81 26.8 337 27.2 9764 24.8
  Two 17 17.2 38 18.7 55 18.2 207 16.7 4792 12.2
  Three 10 10.1 26 12.8 36 11.9 138 11.1 1705 4.3
  Four or more 13 13.1 30 14.8 43 14.2 146 11.8 1006 2.6
  Missing/not stated 0 0.0 0 0.0 0 0.0 0 0.0   39   
Parous   69 69.7 146 71.9 215 71.2 828 66.9 0.1509 17267 43.9 <0.0001
Aboriginal/Torres Strait Islander 28 28.3 56 27.6 84 27.8 255 20.6 0.0068 863 2.2 <0.0001
Born in Australia 85 85.9 181 89.2 266 88.1 1091 88.1 0.9821 27598 70.1 <0.0001
Opioid Substitution Therapy (OST) 4 4.0 3 1.5 7 2.3 76 6.1 0.0034 30 0.1 <0.0001
Mental health admission 25 25.3 57 28.1 81 26.8 318 25.7 2345 6.0
Mental health admission and OST 41 41.4 108 53.2 149 49.3 510 41.2 136 0.3
Mental health admission or OST 70 70.7 168 82.8 237 78.5 904 73 0.0394 2511 6.4 <0.0001
Cigarettes/day (vi)             
  None 23 23.2 29 14.3 52 17.2 287 23.2 0.0802 33699 85.6 <0.001
  1–10 16 16.2 49 24.1 65 21.5 311 25.1 2974 7.6
  >10 46 46.5 112 55.2 158 52.3 605 48.9 2428 6.2
  Missing/not stated 14 14.1 13 6.4 27 8.9 35 2.8   266 0.7  
  Total 99 100.0 203 100.0 302 100.0 1238 100.0   39367 100.0  
  Any smoking during pregnancy 76 76.8 174 85.7 250 82.8 960 77.5 0.0364 5813 14.8 <0.0001
Number of incarcerations (vii)             
  1 35 35.4 67 33.0 102 33.8 711 57.4 <0.0001 n/a n/a  
  2 14 14.1 39 19.2 53 17.5 256 20.7 n/a n/a  
  3 11 11.1 35 17.2 46 15.2 111 9.0 n/a n/a  
  4 12 12.1 15 7.4 27 8.9 67 5.4 n/a n/a  
  5 5 5.1 8 3.9 13 4.3 33 2.7 n/a n/a  
  6–10 17 17.2 32 15.8 49 16.2 55 4.4 n/a n/a  
  11–20 5 5.1 7 3.4 12 4.0 5 0.4   n/a n/a  
Total N   99 100.0 203 100.0 302 100.0 1238 100.0   39367 100.0  
  1. (i) For each group, singleton births and first births during the study period (index births) only.
  2. (ii) Births to women who were incarcerated for a minimum of five consecutive days during this pregnancy.
  3. (iii) Births to women were not incarcerated during this pregnancy, but were incarcerated at another time during the study period.
  4. (iv) A random 10% sample of births to women who were not incarcerated at all during the study period.
  5. (v) One-way ANOVA and Bonferroni tests were used to test for differences between study and control groups in the distribution of maternal age; chi-square tests were used to look for differences between groups for all other maternal demographics.
  6. (vi) Number of cigarettes smoked per day in the second half of pregnancy (from 20 weeks gestational age onwards).
  7. (vii) Number of incarcerations of at least five days’ duration, 1998 to 2006.