Table 3

Crude and adjusted odds ratios for interpregnancy interval and the outcome of the second pregnancy (n=69 055)

Interpregnancy interval*
1-5 months (n=3282)6-11 months (n=8999)12-17 months (n=12 220)18-23 months*24-59 months (n=32 761)
Odds ratio (95% CI)Odds ratio (95% CI)Odds ratio (95% CI)Odds ratio (95% CI)
Outcome of second pregnancyNo (%)CrudeAdjustedNo (%)CrudeAdjustedNo (%)CrudeAdjustedNo (%)No (%)CrudeAdjusted
Birth weight <5th centile99 (3.0)1.1 (0.9 to 1.4)0.8 (0.7 to 1.1)234 (2.6)1.0 (0.8 to 1.1)0.9 (0.8 to 1.1)325 (2.7)1.0 (0.8 to 1.1)1.0 (0.8 to 1.2)321 (2.7)987 (3.0)1.1 (1.0 to 1.3)1.0 (0.9 to 1.1)
Preterm delivery:
24-32 weeks32 (1.0)3.1 (1.9 to 4.9)2.2 (1.4 to 3.6)46 (0.5)1.6 (1.0 to 2.4)1.4 (0.9 to 2.2)48 (0.4)1.2 (0.8 to 1.9)1.2 (0.8 to 1.8)38 (0.3)122 (0.4)1.2 (0.8 to 1.7)1.1 (0.8 to 1.6)
33-36 weeks130 (4.0)2.0 (1.6 to 2.4)1.6 (1.3 to 2.0)218 (2.4)1.2 (1.0 to 1.4)1.1 (0.9 to 1.3)280 (2.3)1.1 (0.9 to 1.3)1.1 (0.9 to 1.3)244 (2.1)800 (2.5)1.2 (1.0 to 1.4)1.2 (1.0 to 1.3)
Perinatal death:
Fetal abnormality or rhesus6 (0.2)1.4 (0.6 to 3.7)1.2 (0.5 to 3.3)12 (0.1)1.0 (0.5 to 2.2)1.0 (0.5 to 2.1)17 (0.1)1.1 (0.5 to 2.2)1.2 (0.5 to 2.2)15 (0.1)45 (0.1)1.1 (0.6 to 1.9)1.1 (0.6 to 2.0)
Unexplained stillbirth7 (0.2)1.6 (0.6 to 3.8)1.2 (0.5 to 3.0)10 (0.1)0.8 (0.4 to 1.8)0.7 (0.3 to 1.7)20 (0.2)1.2 (0.6 to 2.3)1.2 (0.6 to 2.3)16 (0.1)55 (0.2)1.2 (0.7 to 2.2)1.2 (0.7 to 2.1)
All other stillbirths5 (0.2)2.6 (0.8 to 8.1)2.3 (0.7 to 7.2)9 (0.1)1.7 (0.6 to 4.5)1.7 (0.6 to 4.5)12 (0.1)1.7 (0.7 to 4.2)1.7 (0.7 to 4.3)7 (0.1)27 (0.1)1.4 (0.6 to 3.2)1.2 (0.5 to 2.8)
All other neonatal deaths9 (0.3)5.4 (1.9 to 15.2)3.6 (1.2 to 10.7)10 (0.1)2.2 (0.8 to 6.0)1.9 (0.7 to 5.2)2 (0.0)0.3 (0.1 to 1.6)0.3 (0.1 to 1.5)6 (0.1)20 (0.1)1.2 (0.5 to 3.0)1.2 (0.5 to 3.0)
  • All percentages calculated relative to appropriate denominators (see methods).

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

  • †Adjusted for maternal age, marital status, height, socioeconomic deprivation category, smoking, previous birth weight vigesimal, and previous caesarean section.