The reasons for prematurity in anterior placenta remain poorly understood. Previous studies have reported that a short cervical length is associated with preterm delivery not only in women with normal placental position but also in those with placenta previa 18, 19. In this study, although gestational age at delivery was significantly earlier in the anterior groups in complete placenta previa, no significant difference was observed in cervical length at delivery between the anterior and posterior groups. Therefore, complete placenta previa combined with anterior placental location may confer a higher risk of early cervical shortening than incomplete placenta previa or posterior placental location. We speculated that mechanical stimulation of the anterior uterine wall during daily life is more frequent and direct than that of the posterior wall, which is protected by the pelvis. If the placenta is located on the anterior wall, such stimulation may cause uterine contractions and subsequent unknown reactions in the underlying decidua basalis, where abundant blood flow exists. However, a previous study revealed that background uterine electromyographic activity, measured from the abdominal surface in the middle trimester of pregnancy, was independent of placental implantation site 20. Further study is necessary to explore the pathophysiology underlying the clinical differences associated with anterior and posterior placental position in women with complete placenta previa. In conclusion, obstetricians should be aware of the high risk of preterm delivery for antepartum hemorrhage in women with complete placenta previa, particularly when the placenta is located on the anterior uterine wall. Conversely, women with incomplete placenta previa are at relatively low risk of preterm delivery, and the incidence of preterm delivery is not influenced by placental position. Competing Interests The authors have declared that no competing interest exists.