Host defence mechanisms in obstetrics and gynaecology.

The host possesses a variety of defence mechanisms which operate in concert to prevent infection or alter the course of an infective process. The majority of infectious diseases in the gynaecological patient arise at the mucosal surfaces. Mucosal surface pathogens must compete with organisms which are members of the normal flora and with local immunity. In the surgical patient infection usually arises as a result of disruption of anatomical barriers and implantation of organisms from the host's own flora in deeper tissues. Inflammatory and phagocytic reactions provide protection in this setting but their effectiveness may be perturbed by such features of the surgical procedure as leaving devitalized tissue or excessive amounts of suture in the operative site, or by inadequate haemostasis. The pregnant patient appears to have increased phagocytic activity and certain humoral antibacterial factors are also increased. She may have slight alterations in humoral immunity and evidence for altered cell-mediated immunity is provided. Further investigation of host defence in obstetrical and gynaecological patients may produce better methods for identifying defects in resistance to infectious processes and the development of the means for augmenting the natural defences of the host.