This book is about Streptococcus agalactiae and its role in abortion in women. Streptococcus agalactiae or group B streptococcus (GBS) is a commensal organism in humans, but can cause life threatening infection in susceptible hosts such as neonates, pregnant women and non-pregnant adults with chronic illnesses. This book directed about induced proinflammatory cytokine and activated molecules like CD79 and CD54 during infection with streptococcus agalactiae in pregnant women. This response is important in progress placentitis and abortion in women.