Background: Infants born preterm at <37 + 0 weeks of gestation experience systemic complications later in adulthood. However, the risk of adults born preterm delivering preterm babies themselves is not well investigated. Methods: Midwives Notifications of births for the Western Australian population from 1980 to 2010 were obtained. A retrospective cohort study of 958,729 live-born singletons infants was conducted. Logistic regression was used to estimate odds ratios of preterm birth for preterm born parents compared to term born parents. Adjustment was made for socioeconomic status (quintiles of an area level disadvantage score), parity, maternal age, and ethnicity. Results: A total of 876,755 term and 81,974 preterm babies were born during the study period. Information on the preterm birth status of the mother or father was available for 138,123 children. Of these, 1555 (12.08%) children were born preterm to parents born preterm (either of the two parents were preterm), 11,504 (9.22%) preterm children were born to parents born at term, 11,319 term children were born to parents born preterm and 113,254 term children were born to parents born at term. 68,915 (8.39%) preterm children were born where parents’ whose gestational age was unknown. The unadjusted and adjusted odds ratios with and 95% confidence intervals (CI) for the odds of preterm born adults delivering preterm child were 1.35 (1.29–1.42, p <.0001) and 1.25 (1.18–1.32, p <.0001) respectively. The adjusted odds ratio (with 95% CI) for Aboriginal vs Caucasian adults was 1.96 (1.91–2.01, p <.0001). Conclusion: In Western Australia delivering a preterm child is 25% greater when the parent was born preterm than when the parent was born at term in Western Australia. The effect appears to be transgenerational.