Objective: Our purpose was to study low birth weight and preterm birth after short interpregnancy intervals.
Study design: Follow-up of a cohort of a register-based random sample of women who had at least two live births in Denmark between 1980 and 1992. Frequency of preterm birth (gestational age <37 weeks) and low birth weight (<2500 gm) were studied as a function of the interpregnancy interval in 10,187 women.
Results: Short interpregnancy intervals (< or =8 months) were associated with preterm birth but not with low birth weight. The adjusted odds ratios for preterm birth were 3.60 (95% confidence interval 2.04 to 6.35) for intervals up to 4.00 months and 2.28 (1.49 to 3.48) for intervals between 4.01 and 8.00 months compared with deliveries after 24 to 36 months, in which the risk of preterm birth was 3.5%. Risks were higher in women with a previous pregnancy at term. Social status, age, and parity were adjusted for.
Conclusions: Short interpregnancy intervals were associated with an increased risk of premature delivery. This risk should be taken into account when planning a new pregnancy.