Clinical and Subclinical Intrauterine Infection or Inflammation

Intrauterine infection and inflammation are the major causes of preterm labor and/or preterm prelabor rupture of membranes (pPROM). Numerous cytokines and chemokines, matrix metalloproteases, and toll-like receptors are involved in the mechanisms of preterm labor and pPROM. Ascending infection from the vagina and cervix is thought to be the most common pathway of intrauterine infection. The prevalence of positive amniotic cultures is 9–38% in preterm labor with intact membranes and 12–34% in pPROM. Analysis by PCR results in a higher prevalence of 11–56% in preterm labor with intact membranes and 18–50% in pPROM. The optimal diagnostic criteria are not well established. Histological examination of the placenta, fetal membranes, and umbilical cord or amniotic fluid analysis is the gold standard for the diagnosis of intrauterine infection. Multiple organ systems, including the hematopoietic system, thymus, adrenal glands, skin, kidneys, heart, lungs, and brain, are targeted in fetal inflammatory response syndrome. However, there is a lack of robust meta-analysis-based evidence regarding the association between intrauterine infection/inflammation and adverse neonatal outcomes in preterm infants because of various confounding factors.