Ascending Infection of Gestation

Human pregnancies in mid or late stage frequently terminate in premature delivery, and this is often related to ascending infection of the uterus and fetal membranes (chorioamnionitis) and  aspiration pneumonia of the fetus. It is the commonest cause of premature delivery between 20-30 weeks. While it is sometimes this is due to human-specific organisms such as Group B Streptococcus, most cases involve a wide variety of organisms e.g. Mycoplasma, Chlamydia, Candida, etc.  The problem is often recurrent and is probably is a sequel to chronic endocervicitis (inflammation of the cervix of the uterus), which can then lead lead to inflammation of the decidua (the lining of the uterus).   The infiltrating neutrophil leukocytes liberate phospholipases and these are apparently responsible for dilatation of the cervix and premature labor.  Those with practical experience state that this form of pre-maturity due to ascending infection is very uncommon in non-human primates in captivity, particularly in the great apes. The reasons for this apparent difference are unknown. One possibility is that humans often continued to have sex into late stages of pregnancy, perhaps increasing the risk of ascending infection.