PROVIDE INSIGHT INTO THE MECHANISMS OF IDIOPATHIC PRETERM BIRTH IRINA A. BUHIMSCHI, VICTOR A. ROSENBERG, SONYA S. ABDEL-RAZEQ, STEPHEN F. THUNG, CATALIN S. BUHIMSCHI, Yale University, Ob./Gyn.& Reprod.Sci., New Haven, Connecticut OBJECTIVE: Identification of relevant disease biomarkers that may impact prediction of preterm birth (PTB) and fetal outcome is critical. Recent advancement in proteomics has provided a valuable perspective related to several complex functional and molecular mechanisms (inflammation, bleeding) leading to PTB. Still, the etiology of most PTB remains elusive. A comprehensive analysis of the amniotic fluid (AF) proteome was conducted to identify disease biomarker patterns related to PTB in the absence of infection/ inflammation or bleeding. STUDY DESIGN: A proteomic fingerprint was generated from fresh AF using SELDI-TOF mass spectrometry in a total of 268 consecutive samples retrieved from women who presented with signs or symptoms of preterm labor or PPROM. Intra-amniotic inflammation and bleeding were excluded based on previously validated proteomic profiles and biomarker identification. Hierarchical clustering algorithms based on novel descriptors quantifying similarity/dissimilarity among tracings allowed identification of mass areas of interest. RESULTS: The prevalence of PTB !34 wks was 77%. A novel discriminatory profile was identified in the 10-14 kDa area of interest and consisted of 5 proteomic peaks (Q1-5; Figure). The abnormal profile was associated with PTB in the absence of intra-amniotic infection, inflammation or bleeding. Women displaying the novel profile were at 27.1 [16.3-36.1] wks GA at amniocentesis and most often presented with intact membranes. The novel profile appeared alone and all other tests of AF were normal in 85% (17/20) of cases. S6 SMFM Abstracts