Table 3.

 Crude and adjusted odds ratios of adverse pregnancy outcomes for different interpregnancy intervals

Second pregnancy outcomes	Interpregnancy intervals (months)
	<6	12-18	18-24	>24
Miscarriage:
Crude odds ratio (95% CI)	0.77 (0.71 to 0.84)*	0.97 (0.85 to 1.10)	1.01 (0.88 to 1.17)	0.96 (0.86 to 1.06)
Adjusted† odds ratio (95% CI)	0.66 (0.57 to 0.77)*	0.98 (0.80 to 1.21)	0.99 (0.78 to 1.27)	0.99 (0.84 to 1.18)*
Ectopic pregnancy:
Crude odds ratio (95% CI)	0.48 (0.34 to 0.69)*	0.99 (0.62 to 1.56)	0.64 (0.34 to 1.21)	1.87 (1.36 to 2.58)*
Adjusted† odds ratio (95% CI)	0.48 (0.34 to 0.69)*	0.99 (0.63 to 1.57)	0.65 (0.34 to 1.23)	1.97 (1.42 to 2.72)*
Termination:
Crude odds ratio (95% CI)	0.48 (0.41 to 0.56)*	1.22 (1.01 to 1.47)*	1.54 (1.26 to 1.88)*	2.21 (1.93 to 2.54)*
Adjusted† odds ratio (95% CI)	0.43 (0.33 to 0.57)*	1.15 (0.83 to 1.59)	1.55 (1.10 to 2.19)*	2.40 (1.91 to 3.01)*
Stillbirth:
Crude odd ratio (95% CI)	0.72 (0.51 to 1.03)	1.26 (0.79 to 2.02)	0.95 (0.52 to 1.75)	0.98 (0.64 to 1.50)
Adjusted† odds ratio (95% CI)	0.70 (0.38 to 1.29)	1.20 (0.54 to 2.67)	0.83 (0.28 to 2.44)	1.07 (0.54 to 2.15)

Reference category was interpregnancy interval of 6-12 months. Interaction terms interpregnancy interval × year of admission in five year bands were entered into the model, but only that for miscarriage was statistically significant.

*P<0.05.

†Adjusted for maternal age at first pregnancy, Carstairs social deprivation category, and year of first pregnancy.