Objectives To examine the association between prior chlamydia and gonorrhoea infections and adverse obstetric outcomes. Methods Records of women resident in New South Wales, Australia with a singleton first birth during 1999-2008 were linked to chlamydia and gonorrhoea notifications using probabilistic linkage. Obstetric outcomes and potential confounders were ascertained from the birth record. Logistic regression, adjusted for potential confounders was used to estimate the association between a disease notification prior to the birth and adverse birth outcomes: spontaneous preterm birth (SPTB), small for gestational age (SGA) and stillbirth. Results Among 354 217 women, 1.0% (n=3658) had a prior chlamydia notification; 0.06% (n=196) had a prior gonorrhoea notification. The majority of notifications (80%) occurred before the estimated conception date. 4.1% of women had a SPTB, 12.1% had a SGA baby and 0.6% of women had a stillbirth. Among women with a prior chlamydia notification, the risk of SPTB and stillbirth was increased, aOR 1.17 (95% CI 1.01 to 1.37) and aOR 1.40 (95% CI 1.00 to 1.96) respectively but there was no association with SGA, aOR 0.99 (95% CI 0.89 to 1.09). For women with gonorrhoea the risks for SPTB, stillbirth and SGA were respectively aOR 2.50 (95% CI 1.39 to 4.50), 2.35 (95% CI 0.58 to 9.56) and 0.98 (95% CI 0.58 to 1.68). Among women with a prior chlamydia diagnosis, the risk of SPTB did not differ between women diagnosed 1 year prior to conception, within the year prior to conception or during the pregnancy, ( p=0.9). Conclusions Sexually transmissible infections in pregnancy and the preconception period may be important in predicting pregnancy outcomes.