No abstract

The fetal membrane (FM) layers, amnion and choriodecidua, are frequently noted to have varying degrees of separation following delivery. FM layers normally separate prior to rupture during in vitro biomechanical testing. We hypothesized that the adherence between amnion and choriodecidua decreases prior to delivery resulting in separation of the FM layers and facilitating FM rupture.METHODS-FM from 232 consecutively delivered patients were examined to determine the extent of spontaneous separation of the FM layers at delivery. Percent separation was determined by the weight of separated FM tissue divided by the total FM weight. Separately, the adherence between intact FM layers was determined. FM adherence was tested following term vaginal delivery (13), term unlabored cesarean section (10), and preterm delivery (6).RESULTS-Subjects enrolled in the two studies had similar demographic and clinical characteristics. FM separation was present in 92.1% of membranes. Only 4.3% of FM delivered following spontaneous rupture of the fetal membranes (SROM) had no detectable separation. 64.7% of FM had greater than 10% separation. FM from term vaginal deliveries had significantly more separation and were less adherent than FM of term unlabored, elective cesarean section (39.0 ± 34.4% vs 22.5 ± 30.9%, p=.046 and 0.041 ± 0.018 N/cm vs 0.048 ± 0.019 N/cm, p< .005). Preterm FM had less separation and were more adherent than term FM (9.95 ± 17.7% vs 37.5 ± 34.4% and 0.070 ± 0.040 N/cm vs 0.044 ± 0.020 N/cm; both p< .001). Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. CONCLUSIONS-Separation NIH Public Access Author ManuscriptPlacenta. Author manuscript; available in PMC 2011 January 1. separation and decreased adherence are seen both with increasing gestation and with labor suggesting both biochemical and mechanical etiologies. The data are consistent with the hypothesis that FM layer separation is part of the FM weakening process during normal parturition.

We have previously shown that separation of the amnion from choriodecidua occurs as an integral part of the fetal membranes (FM) rupture process. We have also reported that spontaneous separation of FM is nearly universal with term vaginal delivery. The etiology of this spontaneous FM separation is unknown. If biochemical degradation at the amnion-choriodecidua interface is a factor, decreased adhesive force between the FM components prior to their complete separation would be expected. The purpose of this project was to develop and validate machinery and procedures to measure the adhesive force between amnion and choriodecidua. Commercial tensile testing equipment was adapted to perform a standard T-peel test, per the American Society for Testing and Materials (ASTM) guidelines. FM test strip dimensions, peel speed, and peel force data measurements from force versus displacement curves were optimized for reproducibility. Test system validation was performed using Shurtape CP 60 (slow release painter's masking tape) as the standard. Equipment and procedures for a standard T-peel test on FM were developed. Shurtape CP 60 of decreasing widths showed reproducible, linear changes in the adhesive force range for FM (r 2 = 0.96). The adhesive force between FM components ranged from 0.017-0.262 N/cm. Reproducibility was optimal with FM test strips of 4x6 cm and a peel speed of 25.4 cm/min. FM showed greater adhesive force adjacent to the placental disc than distal from the disc (p<0.05). We have developed equipment and procedures to accurately and reproducibly measure adhesive force between the FM amnion and choriodecidua.