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Table 4 Maternal characteristics associated with provider-initiated preterm births

From: Prevalence and risk factors related to preterm birth in Brazil

  Model A Model B Model C
OR adj.g (95 % CI) OR adj.h (95 % CI) OR adj.i (95 % CI)
Level 1 - Sociodemographic characteristics
 Childbirth healthcare (ref: public)
  Private 1.36* 0.98 1.87 1.40* 1.07 1.85 1.47 1.09 1.97
 Age (ref: 20 to 34)
  12 to 19 0.88 0.69 1.12 0.73 0.55 0.95 0.93 0.68 1.20
   ≥ 35 1.60* 1.27 2.02 1.65* 1.30 2.08 1.27 1.01 1.59
 Skin color (ref: white)
  Black 0.82 0.58 1.16       
  brown 1.01 0.84 1.22       
 Marital status (ref:live with partner)
  Do not live with partner 0.85 0.67 1.09       
 Years of schooling (ref: ≥ 15)
   ≤ 7 0.74 0.47 1.17       
  8 to 10 0.74 0.46 1.19       
  11 to 14 0.91 0.60 1.37       
Level 2 - Obstetric history
 Previous births (ref: 1 to 2) a
  0     1.40* 1.16 1.70 1.26 1.04 1.53
   ≥ 3     1.23* 0.94 1.61 1.16 0.89 1.52
 Previous abortionb (ref: no, in women with a previous pregnancy)     1.14 0.84 1.53    
 Previous stillbirth or neonatal deathc (ref: no, in women with a previous delivery)     1.39* 0.93 2.09    
 Previous preterm birthc (ref: no, in women with a previous delivery)     2.84* 2.18 3.70 3.14 2.39 4.11
 Previous caesarean sectionc (ref: no, in women with a previous delivery)
  1     1.41* 1.06 1.87 1.25 0.96 1.62
   ≥ 2     1.91* 1.43 2.55 1.64 1.19 2.26
Level 3 - Maternal/fetal conditions during pregnancy
 Type of pregnancy (ref: single)
  Multiple        20.29 12.58 32.72
 Obstetric risk (ref: no)
  Any below        6.84 5.56 8.42
  Hypertensive disordersd        6.35 4.97 8.12
  Eclampsia        8.67 5.24 14.35
  Preexisting Diabetes        3.60 2.19 5.91
  Gestational Diabetes        2.04 1.58 2.63
  Severe chronic diseasese        3.30 1.80 6.05
  Infection at hospital admission for birth        5.12 1.76 14.89
  Abruptio placentae        7.84 5.04 12.21
  Placental praevia        6.44 3.48 11.90
  IUGR        5.18 3.93 6.83
  Major newborn malformationf        5.55 2.00 15.39
  1. aSeparate models B and C, not including the other obstetric history variables, were performed to estimate OR and 95 % CI for the variable “Previous births”
  2. bPrimigravida women were alocated in a separate category
  3. cNuliparous women were alocated in a separate category
  4. dChronic hypertension, pre-eclampsia and HELLP syndrome
  5. eChronic renal diseases, chronic cardiac diseases and auto-imune diseases
  6. fIncluded anencephaly, hidrocephaly, spina bifida, gastrosquisis and other abdominal wall defects, cardiac malformations and multiple malformations
  7. gadjusted for type of payment of birth, age, skin color, marital status and schooling
  8. hadjusted for type of payment of birth, age, previous births, previous abortion, previous stillbirth or neonatal death, previous preterm births and previous caesaren section
  9. iadjusted for type of payment of birth, age, previous births, previous preterm births, previous caesaren section, type of pregnancy and obstetric risk
  10. *P-value lower than 0.10