INTRODUCTION: Previous studies have reported that maternal asthma increases the risk of preterm birth. We hypothesized that inflammatory reactions caused by allergic diseases might affect the uterine environment and, subsequently, perinatal outcomes. The objective of this study was to examine the associations between allergic features among mothers and preterm pregnancy outcomes in a nationwide birth cohort. METHODS: We analyzed data from pregnant women obtained from the Japanese Environment and Children's Study (JECS), a nationwide general birth cohort study. We used binomial and multinomial logistic regression models to examine the associations between maternal allergic features and preterm birth, threatened preterm labor (TPL), and preterm premature rupture of the membrane (PPROM). RESULTS: A total of 97,683 pregnant women were included. Prevalence of preterm birth, TPL, and PPROM was 4.7, 19.6, and 1.2%, respectively. Maternal history of allergic diseases (asthma, allergic rhinitis, allergic conjunctivitis, food allergy, drug allergy, and contact dermatitis) increased the risk of TPL(adjusted odds ratio [aOR] = 1.11 [95% CI: 1.06-1.17], aOR = 1.12 [1.08-1.16], aOR = 1.10 [1.04-1.16], aOR = 1.17 [1.09-1.26], aOR = 1.35 [1.23-1.48], and aOR = 1.34 [1.20-1.49], respectively). Although some maternal allergic features showed a negative association with preterm birth, the variables affecting preterm birth differed according to the gestational age of the fetus (22-33 weeks vs. 34-36 weeks). There were no significant associations between maternal allergic features and PPROM. CONCLUSION: Maternal allergic disease, except atopic dermatitis, may increase the risk of TPL. Comorbidity of maternal allergic disorders and perinatal adverse outcomes require further investigation.