TABLE 3. Mortality Rates and RRs (±95% CIs) by Gestational Age and Plurality, USA, 1983-1986

Gestation

Fetal

Perinatal

Early Neonatal

Late Neonatal

Neonatal

Postneonatal

Infant

Categories

Single

Twin

Twin RR

Single

Twin

Twin RR

Single

Twin

Twin RR

Single

Twin

Twin RR

Single

Twin

Twin RR

Single

Twin

Twin RR

Single

Twin

Twin RR

(wk)

Rate

Rate

(95% CI)

Rate

Rate

(95% CI)

Rate

Rate

(95% CI)

Rate

Rate

(95% CI)

Rate

Rate

(95% CI)

Rate

Rate

(95% CI)

Rate

Rate

(95% CI)

28–30

81.0

37.1

0.48

136.7

102.9

0.73

66.7

68.4

1.03

21.0

32.0

1.54

87.7

100.4

1.16

31.4

39.8

1.28

119.1

140.2

1.21

 

 

 

(0.41–0.55)

 

 

(0.66–0.79)

 

 

(0.92–1.15)

 

 

(1.31–1.83)

 

 

(1.06–1.28)

 

 

(1.01–1.48)

 

 

(1.11–1.31)

31–34

28.0

17.7

0.64

42.5

28.4

0.66

15.7

10.9

0.69

3.7

4.2

1.12

19.5

15.1

0.77

11.6

13.9

1.20

29.3

30.0

0.95

 

 

 

(0.59–0.70)

 

 

(0.61–0.71)

 

 

(0.61–0.77)

 

 

(0.92–1.35)

 

 

(0.77–0.85)

 

 

(1.08–1.33)

 

 

(0.89–1.02)

35–38

4.8

8.3

1.74

7.2

11.1

1.55

2.4

2.8

1.17

0.9

1.4

1.48

3.3

4.1

1.25

4.1

6.6

1.60

7.4

10.7

1.44

 

 

 

(1.62–1.87)

 

 

(1.46–1.65)

 

 

(1.03–1.33)

 

 

(1.24–1.77)

 

 

(1.13–1.38)

 

 

(1.47–1.73)

 

 

(1.35–1.54)

39–42

1.7

7.3

4.41

2.7

9.5

3.52

1.0

2.1

2.05

0.5

1.2

2.33

1.5

3.3

2.16

2.5

6.0

2.35

4.1

9.3

2.28

 

 

 

(3.99–4.88)

 

 

(3.22–3.85)

 

 

(1.70–2.47)

 

 

(1.80–3.02)

 

 

(1.86–2.51)

 

 

(2.10–2.63)

 

 

(2.08–2.50)


CI = confidence interval; RR = relative risk.
(Luke B, Minogue J: Contribution of gestational age and birth weight to perinatal viability in singletons versus twins. J Matern Fetal med 3:263, 1994)