Department of Pathology, Hutzel Women's Hospital, Wayne State University School of Medicine, Detroit, MI, USA.
J Matern Fetal Neonatal Med. 2022 May;35(10):1853-1859. doi: 10.1080/14767058.2020.1770217. Epub 2020 May 27.
The cause of meconium passage in utero is controversial, traditionally being considered evidence of fetal stress and hypoxia, and also associated with intra-amniotic inflammation/infection. It is now recognized to also occur in the absence of fetal stress. Autopsy studies have shown that many term stillborns (SB) have hypoxic/ischemic brain injury and other evidence of stress preceding the time period immediately before demise, including acute thymic involution (ATI); however, these findings, along with placental findings, have not been previously correlated with meconium-stained amniotic fluid (MSAF).
35 structurally normal singleton term SB (21 early term, 14 full/late term) with complete autopsies, including brain and placental examination, were identified. MSAF was visually identified at delivery and confirmed on the placental examination. Autopsy evaluation included brain injury and ATI. Placental evaluation included maternal and fetal vascular malperfusion and acute and chronic inflammatory lesions. Demographic and clinical features were compared.
18 (51%) SB had MSAF, and 17 (49%) had clear amniotic fluid (CAF). The was no significant difference in brain injury in the MSAF vs CAF group, including older gray matter injury (karyorrhexis) (67% vs 47%), recent gray matter injury (red neurons, but no karyorrhexis) (28% vs 35%), white matter injury (50% vs 29%), and hemorrhage (22% vs 24%). Severe ATI was more frequent in the MSAF vs CAF group (61% vs 24%, = .04). There was no significant difference in placental lesions between groups, including acute maternal inflammation (39% vs 18%), acute fetal inflammation (6% vs 6%), fetal vascular malperfusion (11% vs 18%), maternal vascular malperfusion (39% vs 35%), and chronic inflammatory lesions (39% vs 29%). The MSAF group was more likely to be full/late term than early term (72% vs 28%), in contrast to the CAF group (6% vs 94%) ( = .0001). There was no difference in other clinical factors evaluated.
51% of term SB had MSAF, and, in contrast to the CAF group, these were significantly more likely to be full/late term. Brain injury was frequent in both MSAF and CAF groups, supporting hypoxia as the mechanism of demise in most of these SB. No placental lesions correlated with MSAF, including inflammation. This suggests that hypoxia is the cause of the MSAF in these SB, but that some additional biologic factor present in the full/late term SB, but not present in the early term SB, including possibly gastrointestinal maturation, is necessary for the meconium passage.
胎儿在子宫内排粪的原因尚存在争议，传统上被认为是胎儿应激和缺氧的证据，也与羊膜内炎症/感染有关。现在也认识到它也会在没有胎儿应激的情况下发生。尸检研究表明，许多足月死胎（SB）在死亡前的时间内有缺氧/缺血性脑损伤和其他应激证据，包括急性胸腺萎缩（ATI）；然而，这些发现，连同胎盘发现，以前与胎粪污染的羊水（MSAF）无关。
确定了 35 例结构正常的单胎足月 SB（21 例早期足月，14 例足月/晚期足月），并进行了完整的尸检，包括脑和胎盘检查。MSAF 在分娩时通过肉眼观察识别，并在胎盘检查中得到证实。尸检评估包括脑损伤和 ATI。胎盘评估包括母体和胎儿血管灌注不良以及急性和慢性炎症病变。比较了人口统计学和临床特征。
18 例（51%）SB 有 MSAF，17 例（49%）有清亮羊水（CAF）。MSAF 组与 CAF 组的脑损伤无显著差异，包括较老的灰质损伤（核碎裂）（67% vs 47%）、近期灰质损伤（红色神经元，但无核碎裂）（28% vs 35%）、白质损伤（50% vs 29%）和出血（22% vs 24%）。MSAF 组的严重 ATI 较 CAF 组更为常见（61% vs 24%，=0.04）。两组间胎盘病变无显著差异，包括急性母体炎症（39% vs 18%）、急性胎儿炎症（6% vs 6%）、胎儿血管灌注不良（11% vs 18%）、母体血管灌注不良（39% vs 35%）和慢性炎症病变（39% vs 29%）。MSAF 组更有可能是足月/晚期足月，而不是早期足月（72% vs 28%），而 CAF 组则相反（6% vs 94%）（=0.0001）。评估的其他临床因素无差异。
51%的足月 SB 有 MSAF，与 CAF 组相比，这些 SB 更有可能是足月/晚期足月。MSAF 组和 CAF 组的脑损伤都很常见，这支持缺氧是这些 SB 死亡的机制。没有与 MSAF 相关的胎盘病变，包括炎症。这表明缺氧是这些 SB 中 MSAF 的原因，但在足月/晚期足月 SB 中存在一些额外的生物学因素，而在早期足月 SB 中不存在，包括可能是胃肠道成熟，这是胎粪排出所必需的。
