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Table 3 Adjusted hazard ratios of reproducing in twins vs. singletons (HR) in males and females and in sub-groups defined by age and birth characteristics

From: Reproductive patterns among twins - a Swedish register study of men and women born 1973-1983

 

Female

Male

 

HRa

95% CI

HRb

95% CI

HRa

95% CI

HRb

95% CI

Age

        

 <= 25 years

0.86

(0.81-0.91)

0.92

(0.86-0.97)

0.91

(0.84-0.98)

0.90

(0.84-0.98)

 >25 years

0.91

(0.87-0.96)

0.95

(0.90-1.00)

0.93

(0.87-0.99)

1.01

(0.94-1.08)

Year of birth

        

 1973-1975

0.93

(0.88-0.98)

0.96

(0.91-1.02)

0.96

(0.89-1.03)

1.01

(0.94-1.09)

 1976-1979

0.87

(0.82-0.92)

0.88

(0.83-0.94)

0.89

(0.82-0.96)

0.92

(0.84-1.00)

 1980-1983

0.83

(0.75-0.91)

0.82

(0.74-0.91)

0.84

(0.72-0.99)

0.84

(0.72-0.98)

Gestational age

        

 Term (37–42 weeks)

0.92

(0.88-0.96)

0.92

(0.88-0.96)

0.94

(0.89-1.00)

0.97

(0.91-1.03)

 Post term (>42 weeks)

0.72

(0.46-1.15)

0.70

(0.44-1.12)

0.98

(0.55-1.79)

1.03

(0.57-1.88)

 Preterm (32–36 weeks)

0.85

(0.78-0.91)

0.86

(0.79-0.92)

0.89

(0.80-0.98)

0.90

(0.81-0.99)

 Very preterm (<32 weeks)

1.28

(1.02-1.62)

1.29

(1.02-1.63)

1.34

(1.01-1.78)

1.33

(1.00 -1.77)

Birthweight

        

 Normal birthweight (≥2500 g)

0.90

(0.85-0.94)

0.90

(0.86-0.94)

0.92

(0.86-0.98)

0.92

(0.87-0.98)

 Low birthweight (1500–2499 g)

0.91

(0.86-0.97)

0.92

(0.86-0.98)

1.05

(0.96-1.16)

1.04

(0.95-1.15)

 Very low birthweight (<1500 g)

1.11

(0.84-1.46)

1.10

(0.83-1.46)

0.81

(0.52-1.25)

0.79

(0.51-1.24)

Size for gestational age

        

 Appropriate for gestational age

0.87

(0.84-0.91)

0.89

(0.85-0.93)

0.91

(0.86-0.96)

0.93

(0.88-0.99)

 Small for gestational age

0.93

(0.86-1.00)

0.96

(0.88-1.03)

1.04

(0.92-1.16)

1.09

(0.97-1.23)

 Large for gestational age

1.15

(0.70-1.88)

1.22

(0.74-2.02)

0.72

(0.34-1.50)

0.78

(0.36-1.69)

Optimality at birth

        

 Optimal$

0.90

(0.86-0.93)

0.90

(0.86-0.93)

0.92

(0.87-0.97)

0.92

(0.87-0.97)

 Non-optimal$$

0.88

(0.86-0.95)

0.91

(0.86-0.96)

0.95

(0.88-1.02)

0.99

(0.92-1.07)

  1. aAdjusted for socio demographic variables presented in Table 1.
  2. bAdjustedfor socio demographic and birth characteristics presented in Table 1.
  3. $Optimal birth characteristics include persons who were not SGA, LGA or preterm at birth.
  4. $$Non-optimal birth characteristics include those who were born SGA, LGA and preterm.
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BMC Pregnancy and Childbirth

ISSN: 1471-2393

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