Premature Rupture Of Membranes (PROM) is a problem related to maternal death caused by infection. In Indonesia, it is estimated that every year 20-30% of women experience PROM. One way to prevent PROM is by giving vitamin C. The purpose of this study is to uncover new things, namely the effectiveness of supplement vitamin C in pregnant women, to prevent the occurrence of PROM. This research is quasi-experimental. The study population was all pregnant women with predisposing factors. The sample in this study, most pregnant women, aged 20 weeks with predisposing factors of PROM who met the inclusion and exclusion criteria were 200 pregnant women, consisting of 100 pregnant women in the experimental group and 100 pregnant women in the control group. Data processing uses univariate, bivariate, and multivariate analysis. Data collection is done by observation at the time of delivery. The results of the study of 100 pregnant women in the experimental group were 6% who experienced PROM after consuming vitamin C while out of 100 pregnant women in the control group who experienced PROM as much as 56%. The results of the study prove that the provision of vitamin C in pregnant women is effective in preventing the incidence of premature rupture of membranes (OR = 13,184). This study concludes that to prevent the occurrence of premature rupture of the membranes it is recommended that pregnant women starting at gestational age 20 weeks consume vitamin C 100 mg/day.