After inclusion into the study, prenatal care will be exactly the same as is our standard for such patients at risk for early delivery with the exception of the weekly administration of the study medicine or placebo. For example, weekly prenatal visits, cervical examinations, ultrasounds, steroids and/or tocolytic treatment (given when preterm labor is diagnosed) will be the same regardless of the group to which the patient is randomized. All groups will have one tube of blood drawn from the placental cord at the time of delivery. There will be no additional visits or costs due to the study itself.