Gestational age at preterm PROM ( odds ratio [ OR ] 0.75 , 95 % confidence interval [ CI ] 0.63-0 .90 for each week after 24 weeks of gestation ) and cervical dilation at admission ( OR 0.66 , 95 % CI 0.49-0 .90 for each centimeter of dilation ) were inversely associated with a latency period of at least 1 week .