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16: Differential remodeling of the fetal chorion among women with preterm premature rupture of membranes

      Objective

      Membrane thinning and remodeling likely contributes to the pathogenesis of PPROM. We sought to quantify fetal chorion thickness, using samples proximate and distant from the rupture site. Our objective was to determine the thickness of the chorion and choriodecidua layer of fetal membranes among PPROM, preterm labor (PTL), preterm no labor (PTNL), term labor (TL), and term subjects without labor (TNL).

      Study Design

      Paired membrane samples were collectedprospectively from women with PPROM, PTL, PTNL, TL, and TNL. Immunohistochemistry was performed on histologic sections with cytokeratin staining of the chorion. Using the Zeiss AxioImager, 1 image per quadrant, 4 quadrants per roll, 4 rolls per slide were obtained for a minimum of 16 images per slide. Using ImageJ® software, chorion and choriodecidual thickness were measured in 4 distinct regions of each image (minimum 48 measurements per slide). Mean chorion thickness for each group was compared. Statistical analysis was performed using Paired t-test, ANOVA, and Student's t test where appropriate.

      Results

      Among all subjects (n=40; 8 in each group), mean chorion thickness at rupture site was less than distant from rupture site (165.6 vs 260.6 μm, p=0.0001). There was no difference in thickness of chorion and choriodecidua layers by gestational age or labor status. When PPROM subjects were compared to all preterm (PTL + PTNL) and term births (TL + TNL), the chorion layer was significantly thinner (figure). In contrast, the choriodecidua layer was similar among all groups.

      Conclusions

      The chorion layer of fetal membranes is thinner at the membrane rupture site compared to distant from rupture for all subjects, regardless of gestational age or labor status. In PPROM, the chorion layer is thinner at both the rupture site and distant from the rupture site suggesting a process that affects the entire fetal membranes; not localized to the rupture site. Understanding the processes leading to premature destruction of the chorion layer may provide important insights into the pathophysiology leading to PPROM.