The Effect of Sulfasalazine on CRH Levels in Pregnant Women

The goal of this randomized clinical trial is to assess sulfasalazine as a potential treatment to prevent recurrent preterm birth. The main questions it aims to answer are: * Does sulfasalazine down regulate corticotropin releasing hormone (CRH) levels in pregnant persons with a prior history of preterm birth? * Does sulfasalazine reduce the incidence of recurrent preterm birth in pregnant persons given drug vs. controls? Consenting participants will be randomized to receive sulfasalazine or to a control group and will undergo serial blood draws to assess plasma CRH levels.