 A sample size estimation indicates that 240 patients 80 in each group will be necessary to have an 80 power decreasing deliveries at 32 weeks by 50 of detecting a significance of 0.05 in the number of preterm births. Likewise, in the 4cm group assuming 90 delivery within seven days 40 patients in each group 120 women will be necessary to have an 80 power of detecting with a 25 reduction in deliveries with seven days a significance of 0.05. It is anticipated that it will take a time period of approximately two years to enroll this number of participants. 