Marinovich ML, Regan AK, Gissler M, et al. - Via performing this cohort study of women who gave birth to first and second (n = 3,213,855) singleton livebirths, researchers here examined the effect of interpregnancy interval (IPI) on preterm birth (PTB; gestational age < 37 weeks) according to whether the previous birth was preterm or term. For each IPI, absolute risk of PTB of 3%–6% after a previous term birth and 17%–22% after previous PTB were reported. Observations revealed modification of associations between IPI and PTB by whether or not the previous pregnancy was preterm. Women with a previous term birth had higher ORs for short and long IPIs vs those with a previous PTB, which for short IPI is consistent with the maternal depletion hypothesis. Given the high risk of recurrence and considering a causal link between IPI and PTB, IPI remains a potentially modifiable risk factor for women with previous PTB.