Table 1

Outcome of first pregnancy in relation to interval between first and second pregnancies (n=89 143)

Interpregnancy interval*
1-5 months6-11 months12-17 months18-23 months*24-59 months
Outcome of first pregnancyNo (%)Odds ratio (95% CI)No (%)Odds ratio (95% CI)No (%)Odds ratio (95% CI)No (%)No (%)Odds ratio (95% CI)
No of births481611 92715 77115 01441 615
Birth weight <5th centile298 (6.6)1.3 (1.1 to 1.5)613 (5.2)1.0 (0.9 to 1.1)804 (5.1)1.0 (0.9 to 1.1)768 (5.1)2347 (5.6)1.1 (1.0 to 1.2)
Preterm delivery:
24-32 weeks146 (3.2)4.1 (3.2 to 5.3)181 (1.5)1.9 (1.5 to 2.4)155 (1.0)1.2 (1.0 to 1.6)120 (0.8)458 (1.1)1.4 (1.1 to 1.7)
33-36 weeks257 (5.9)1.5 (1.3 to 1.7)570 (4.9)1.2 (1.1 to 1.4)662 (4.3)1.1 (1.0 to 1.2)592 (4.0)1830 (4.4)1.1 (1.0 to 1.2)
Perinatal death:
All causes481 (10.0)24.4 (18.9 to 31.5)247 (2.0)4.6 (3.5 to 6.1)103 (0.6)1.4 (1.1 to 2.0)68 (0.4)120 (0.3)0.6 (0.5 to 0.9)
Fetal abnormality or rhesus71 (1.5)15.0 (8.6 to 26.1)38 (0.3)3.2 (1.8 to 5.8)21 (0.1)1.3 (0.7 to 2.6)15 (0.1)26 (0.1)0.6 (0.3 to 1.2)
Unexplained stillbirth188 (3.9)30.5 (19.2 to 48.3)87 (0.7)5.5 (3.4 to 9.0)37 (0.2)1.8 (1.0 to 3.0)20 (0.1)36 (0.1)0.6 (0.4 to 1.1)
All other stillbirths109 (2.3)20.4 (12.2 to 34.1)55 (0.5)4.1 (2.4 to 7.0)21 (0.1)1.2 (0.6 to 2.2)17 (0.1)24 (0.1)0.5 (0.3 to 0.9)
All other neonatal deaths110 (2.3)23.4 (13.6 to 40.1)65 (0.5)5.5 (3.1 to 9.6)23 (0.2)1.5 (0.8 to 2.8)15 (0.1)34 (0.1)0.8 (0.4 to 1.5)
  • All percentages calculated relative to appropriate denominators (see methods).

  • *Reference category for odds ratios was women with interpregnancy interval of 18-23 months.

  • †Seven perinatal deaths were not classified.