BACKGROUND: Diseases and maternal poor habits before conception and during pregnancy have been considered as the definite risk factors for premature delivery and one of the results with better repeatability in the studies on the pathogenesis, whether parental socioeconomic status is related to the occurrence of premature birth?OBJECTIVE: To investigate the association of parental socioeconomic status with premature birth.DESIGN: A case-control study with the parents who has premature infants or normal infants as subjects.SETTING: Department of Preventive Medicine, Medical College of Qingdao University;Woman's Department of Traditional Chinese Medicine, Qingdao Municipal Haici Medicine Group; Department of Obstetric and Gynecology, Qingdao Municipal Eighth People's Hospital PARTICIPANTS: A cohort of premature infants (n=227) were recruited from Qingdao Municipal Maternity and Children Health Institute and the Eighth People's Hospital, Qingdao, premature birth were confirmed according to the diagnostic standards; the control infants (n=750) were also recruited from the same place, they were delivered at pregnancy of from 38 to 42 weeks with birth mass of 3 000-4 000 g. Two groups were matched in sexual constitution and the birthday of within the same week.METHODS: Parents of two groups were asked to fill the self-made questionnaire. Maternal obstetric factors were referring to the perinatal booklet and infant birth record; meanwhile parental socio-economic status, daily-life behaviours and sociodemographic character were also investigated. Multivariate non-conditioned logistic regression analysis was used to assess the relationship of correlative factors.MAIN OUTCOME MEASURES: Parental school education, occupation, the annual family income, as well as bad living and behavioral habits.RESULTS: According to the real state, data of 227 premature infants and 750 normal control infants were analyzed finally. Maternal delivery age of ＞ 35 years old (≤ 25 years old in normal control group), working as a teacher or unemployment (worker in control group), smoking and drinking during pregnancy, father's occupation as peasant (worker in control group), with a long smoking history, lower parental education (not lower than junior college education in control group) and family income less than 35 thousand Yuan (more than 35 thousand Yuan in control group) were proved to be the significant risk factors for premature birth (OR =1.629-15.701).CONCLUSION: Maternal employment as a teacher with father as a peasant, together with lower family income and lower parental education are connected with premature delivery.