Vaginal versus cervical types of visible fetal membranes in cervical insufficiency: clinical characteristics and pathophysiology

This study aimed to compare the clinical, inflammatory, and microbiological characteristics of vaginal and cervical types of visible fetal membranes in cervical insufficiency. We retrospectively analyzed 103 singleton pregnant women, classified into vaginal type (V-type; n = 39) and cervical type (Cx-type; n = 64) based on the extent of membrane descent. Cases were most commonly diagnosed at 20–22 weeks of gestation. V-type cases were associated with significantly worse pregnancy outcomes than Cx-type cases, including a higher rate of spontaneous preterm delivery before 28 weeks (97.4% vs. 59.4%, p < 0.01), a shorter duration of pregnancy prolongation (1 vs. 24 days, p < 0.01), and earlier gestational age at delivery (22 vs. 27 weeks, p < 0.01). Inflammatory markers, including cervical mucus and amniotic fluid interleukin-8, were significantly elevated in V-type cases. Intra-amniotic microbes were more frequently detected in V-type cases, including a higher detection rate of Ureaplasma spp. V-type cases were associated with more severe inflammatory and microbiological abnormalities and poorer pregnancy outcomes than Cx-type cases. However, the temporal and causal relationships among membrane descent, intra-amniotic inflammation, and microbial invasion remain unclear.