Table 3

Birth outcomes among twins by birth order

Twin pregnancies (N=1859, resulting in 3718 infants)Singleton pregnancies (N=117 594)RR (singleton vs any twin)aRR* (singleton vs any twin)
Twin 1
N=1859 (Infants)
Twin 2
N=1859 (Infants)
Any twin
N=1859 (Pregnancies)
Both twins
N=1859 (Pregnancies)
Low birth weight (<2500 g)1158 (62.4%)1239 (67.0%)1430 (77.1%)967 (52.0%)16 019 (13.6%)5.7 (95% CI 5.5 to 5.8)4.5 (95% CI 4.3 to 4.6)
Missing (N,%)4944138
Very low birth weight (<1500 g)237 (12.8%)271 (14.6%)311 (16.8%)197 (10.6%)3757 (3.2%)5.2 (95% CI 4.7 to 5.8)5.2 (95% CI 4.7 to 5.8)
Missing (N,%)4944138
Stillbirth70/1859 (3.8%)96/1855 (5.2%)128 (6.9%)38 (2.0%)2845 (2.4%)2.8, (95% CI 2.4 to 3.4)2.8 (95% CI 2.3 to 3.3)
Missing (N,%)044018
  • *Adjusted for maternal age, gravida and educational attainment and maternal HIV status.

  • aRR, adjusted risk ratio; RR, relative risk.