Background: The current evidence implicates that psychosocial stress, especially pregnancy-specific stress, is associated with the risk of spontaneous preterm birth.The aim of the present study was to determine the effect of pregnancy-specific stress on spontaneous preterm birth among Chinese people. Materials and Methods: A total of 2,189 pregnant women were enrolled and followed up until parturition from February 2011 to January 2012. Maternal pregnancy-specific stress was assessed using the revised Pregnancy Stress Rating Scale (PSRS) at third trimester in pregnancy. Socio-demographic and psychological data were collected through interviews, medical, and obstetrical examination records. Results: High levels of maternal pregnancy-specific stress during the third trimester increased risk of spontaneous preterm birth compared with the low and medium levels (adjusted risk ratios, 2.92; 95% confidence interval, 1.12 - 7.58). The first stressor from the revised PSRS includes a risk factor for the safety of infants. Conclusions: High level of pregnancyspecific stress in third trimester might predict spontaneous preterm birth.