Abstract: Objective：To observe the birth process characteristics of primiparas via vaginal delivery macrosomia and the influence on maternal and infant，so as to make reasonable arrangements to the delivery mode of macrosomia，ensure the safety of maternal and infant. Methods：From January 2008 to December 2010 in our hospital，the data of 88 cases of fetal macrosonia with trial of labor and 60 normal newborns with trial of labor，60 cases of fetal macrosonia with selective cesarean section were subjected to retrospective analysis. Results：Of 88 deliveries of primiparas，43 cases succeeded in vaginal delivery compared with the normal controls，the study group showed shortened latent phase of labor（P＜0.05），prolonged active phase and second stage of labor（P＜0.05），while the total duration of labor were not significantly different between the two groups（P＞0.05）. 45 cases of failed vaginal delivery primiparas were mainly in the protracted active phase，when cervical dilatation was usually 3- 5 cm. Vaginal delivery failure did not increase the rate of postpartum hemorrhage，puerperal infection，and neonatal asphyxia. Conclusions：If there is no obvious cephalopelvic disproportion，normal delivery could be tried. If there is abnormal stages of labor，such as protracted active phase，it needs to divert cesarean section in time，which can reduce the damage of the macrosomia on maternal and infant.

Key words: Fetal macrosomia, Labor presentation, Parturition, Retrospective studies, Cesarean section, Pregnancy outcome