Table 2 Baseline and pregnancy-related characteristics and outcomes of interest - Unadjusted ORs

   < 25

0.61, 1.57

0.80, 1.97

0.49, 0.92

  25–30

–

–

–

  30–35

0.60, 1.55

0.46, 1.27

0.83, 1.48

   > 35

0.54, 1.79

0.56, 1.87

1.09, 2.19

  Kuwaiti

–

–

–

  Non- Kuwaiti

0.39, 0.85

0.71, 1.71

1.05, 1.82

  Employed

–

–

–

  Housewife

0.61, 1.32

0.67, 1.46

0.76, 1.23

  Unemployed

0.37, 1.47

0.40, 1.59

0.29, 0.76

  Up to High School

0.62, 1.39

1.02, 2.18

0.74, 1.21

  Higher education

–

–

–

   < 400

0.37, 1.12

1.09, 3.83

0.60, 1.32

  400–800

0.35, 1.04

0.54, 2.03

0.93, 1.95

  800–1600

0.48, 1.52

0.46, 1.98

0.95, 2.11

   ≥ 1600

–

–

–

  Primiparous

0.62, 1.37

0.82, 1.76

0.42, 0.71

  Multiparous

–

–

–

   < 18.5

0.60, 5.15

0.43, 3.67

0.06, 0.97

  18.5–25

–

–

–

  25–30

0.96, 2.23

0.49, 1.15

1.12, 1.91

   ≥ 30

0.75, 2.03

0.36, 1.04

1.18, 2.14

  No

–

–

–

  Yes

2.10, 9.19

0.31, 3.38

0.63, 2.55

  No previous pregnancy

–

–

  No preterm delivery

0.64, 1.53

0.55, 1.23

1.35, 2.38

  At least one preterm delivery

1.69, 5.68

0.47, 2.13

1.02, 2.78

  No

–

–

–

  Yes

0.81, 4.17

0.66, 3.75

0.96, 2.86

  No

–

–

–

  Yes

1.00, 3.48

0.51, 2.30

1.12, 2.54

  Female

–

–

–

  Male

0.69, 1.43

0.39, 0.83

1.58, 2.54

   < 10

–

–

–

   ≥ 10

0.79, 1.89

0.91, 2.15

0.84, 1.49