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. Author manuscript; available in PMC: 2016 Oct 1.
Published in final edited form as: Am J Obstet Gynecol. 2015 Oct;213(4 0):S29–S52. doi: 10.1016/j.ajog.2015.08.040

Figure 7.

Figure 7

The stages of ascending infection in preterm labor. Stage I in the process of ascending infection is corresponding to a change in the vaginal/cervical microbial flora or the presence of pathologic organisms in the cervix. Once microorganisms gain access to the amniotic cavity, they reside in the lower pole of the uterus between the membranes and the chorion (Stage II). The microorganisms may invade the fetal vessels (choriovasculitis) or proceed through the amnion (amnionitis) into the amniotic cavity leading to an intra-amniotic infection (Stage III). The microorganisms may invade the fetus by different ports of entry (Stage IV). Modified from Figure 1 in Romero R, Mazor M, Infection and Preterm Labor, Clinical Obstetrics and Gynecology;31:1988:553-584.