Abstract: Objective：To compare the cervical ripening effect of two different volume cervical dilatation balloon in full-term pregnancy. Methods：From June 2017 to December 2017, 400 cases of full-term pregnant women with cervical Bishop score ＜6 who were admitted to our hospital for induction were selected randomly. According to the volume of Foley catheter (30 mL and 60 mL), the patients were divided into two groups (200 cases in each) and then the cervical ripening and other pregnancy related prognosis were compared. Results：There is no significant differences between the Bishop scores of two groups before Foley balloon placement ( χ2=1.280, P=0.201). However, after cervical ripening, an obvious difference was demonstrated ( χ2=-4.137, P=0.000). The induction-labor interval of 60 mL Foley catheter was shorter than 30 mL Foley catheter for the nulliparous women (t=4.204, P=0.000). By multivariate analysis, the volume of Foley catheter exerted significant effect on the delivery within 24 hours of induction (OR=1.990, 95%CI: 1.444～2.742, P=0.000). Among 20 cases with previous cesarean section, 18 cases delivered vaginally successfully without any complications. There was no obvious difference observed between the neonatal prognosis of two groups (P＞0.05). Conclusions：Foley catheter is safe and efficient in promoting cervical ripening for full-term pregnant women (including VBAC). Compare to 30 mL volume Foley catheter, 60 mL volume Foley catheter is more effective in promoting cervical maturation, and can shorten the labor induction-delivery time.

Key words: Labor, induced, Term birth, Cervical ripening, Foley catheter