LAUSR

BACKGROUND Studies on Chlamydia trachomatis associated pregnancy outcomes are largely conflicting, ignoring the heterogeneous natures of pregnancy complications and potential effect modification by maternal age. This study determined if prenatal Chlamydia trachomatis infection is associated with preterm birth (PTB) and preeclampsia subtypes. METHODS A retrospective cohort study was conducted using 22,772 singleton pregnancies with a prenatal C. trachomatis diagnostic test. Spontaneous and medically indicated preterm births, term and preterm preeclampsia were outcomes. Modified Poisson regression calculated relative risk (RR) and 95% confidence intervals (CI) with propensity score adjustments stratified by maternal age <25 and ≥25. RESULTS Overall, C. trachomatis was significantly associated with term preeclampsia (RRadj=1.88 95% CI 1.38-2.57). Among young women (age<25), C. trachomatis was significantly associated with medically indicated preterm birth (RRadj=2.29 CI 95% 1.38-3.78) and term preeclampsia (RRadj=1.57 CI 95% 1.05-2.36) in propensity adjusted models. No significant associations in older women were detected. CONCLUSION C. trachomatis was associated with medically indicated preterm birth and term preeclampsia in young women. Associations between chlamydia and perinatal outcomes may depend on the subtype of preterm birth and preeclampsia, which should be investigated through mechanistic studies.