Result: Premature rupture of membranes and multiple pregnancy are the former two reasons causes premature,premature pregnancy is also related to prenatal care, and another 11.63 percent is unknown.

• 结果:胎膜早破、多胎妊娠为早产原因的前二位；早产还与孕期母亲未作产前检查相关；另有11.；63%25为不明原因的早产。