Departments of Pediatrics, Case Western Reserve University (CWRU), MetroHealth Medical Center, 2500 MetroHealth Drive, Cleveland, OH, USA.
Placenta. 2010 Jan;31(1):18-24. doi: 10.1016/j.placenta.2009.10.012. Epub 2009 Nov 17.
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.
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).
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+/-0.018N/cm vs 0.048+/-0.019N/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+/-0.040N/cm vs 0.044+/-0.020N/cm; both p<.001).
Separation of the amnion from choriodecidua at delivery is almost universal. Increased separation is associated with decreased adherence as measured in vitro. Increased 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.
胎膜（FM）的各层，包括羊膜和绒毛蜕膜，在分娩后常被发现有不同程度的分离。在体外生物力学测试中，FM 层通常在破裂前分离。我们假设在分娩前，羊膜和绒毛蜕膜之间的粘连减少，导致 FM 层分离并促进 FM 破裂。
检查了 232 例连续分娩患者的 FM，以确定分娩时 FM 层自发分离的程度。通过分离的 FM 组织重量除以总 FM 重量来确定分离的百分比。另外，还确定了完整 FM 层之间的粘连。分别测试了足月阴道分娩（13 例）、足月无临产剖宫产（10 例）和早产分娩（6 例）后 FM 的粘连。
两项研究的受试者具有相似的人口统计学和临床特征。92.1%的胎膜存在分离。只有 4.3%的胎膜在胎膜自发性破裂（SROM）后没有明显的分离。64.7%的 FM 分离超过 10%。足月阴道分娩的 FM 分离程度更高，粘着力更低，与足月无临产、选择性剖宫产的 FM 相比（39.0+/-34.4%对 22.5+/-30.9%，p=.046 和 0.041+/-0.018N/cm 对 0.048+/-0.019N/cm，p<.005）。早产 FM 的分离程度较低，粘着力较高，与足月 FM 相比（9.95+/-17.7%对 37.5+/-34.4%和 0.070+/-0.040N/cm 对 0.044+/-0.020N/cm；均 p<.001）。
分娩时羊膜与绒毛蜕膜的分离几乎是普遍的。体外测量发现，分离程度增加与粘着力降低有关。随着胎龄的增加和产程的进展，分离程度增加和粘着力降低均可见，提示存在生化和机械两种病因。这些数据与 FM 层分离是正常分娩过程中 FM 弱化过程的一部分的假设是一致的。
