This structured review discusses the current literature on selected biomarkers and their ability to predict preterm delivery (PTD). Among symptomatic women, the likelihood ratio (LR+) for the prediction of PTD was found to be greater than 10 using amniotic fluid (AF) interleukin-6 (IL-6), AF Ureaplasma urealyticum, as well as a multi-marker consisting of cervical IL-6, cervical IL-8, and cervical length (CL). The LR+ was found to be between 5 and 10 for serum C-reactive protein (CRP). An LR+ between 2.5 and 5 was recorded for serum corticotropin-releasing hormone (CRH), cervical fetal fibronectin (fFN), cervical IL-6, serum relaxin, and a multi-marker consisting of fFN and CL. CL and bacterial vaginosis (BV) both predicted PTD in women with preterm labor with an LR+ of less than 2.5. In asymptomatic women, AF U. urealyticum and a multimarker consisting of five individual markers [fFN, CL, serum alpha-fetoprotein (AFP), serum alkaline phosphatase, and serum granulocyte colony-stimulating factor (G-CSF)] predicted PTD with an LR+ greater than 10. The LR+ was between 5 and 10 for serum relaxin and CL. LRs+ recorded for serum alkaline phosphatase, salivary estriol, serum CRH, serum G-CSF, cervical IL-6, AF IL-6, cervical fFN, AFP, and Chlamydia all ranged between 2.5 and 5. Finally, an LR+ below 2.5 has been documented for serum ferritin, serum CRP, BV, and cervical ferritin.