Pregnancy Research Branch, Division of Obstetrics and Maternal-Fetal Medicine, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, United States Department of Health and Human Services, Bethesda, MD, and Detroit, MI; Department of Obstetrics and Gynecology, Wayne State University School of Medicine, Detroit, MI; Department of Gynecology and Obstetrics, Universidad Del Valle, Cali, Colombia.
Pregnancy Research Branch, Division of Obstetrics and Maternal-Fetal Medicine, Division of Intramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, United States Department of Health and Human Services, Bethesda, MD, and Detroit, MI; Department of Obstetrics and Gynecology, University of Michigan, Ann Arbor, MI; Department of Epidemiology and Biostatistics, Michigan State University, East Lansing, MI.
Am J Obstet Gynecol. 2023 May;228(5S):S1158-S1178. doi: 10.1016/j.ajog.2022.11.1283. Epub 2023 Apr 1.
Green-stained amniotic fluid, often referred to as meconium-stained amniotic fluid, is present in 5% to 20% of patients in labor and is considered an obstetric hazard. The condition has been attributed to the passage of fetal colonic content (meconium), intraamniotic bleeding with the presence of heme catabolic products, or both. The frequency of green-stained amniotic fluid increases as a function of gestational age, reaching approximately 27% in post-term gestation. Green-stained amniotic fluid during labor has been associated with fetal acidemia (umbilical artery pH <7.00), neonatal respiratory distress, and seizures as well as cerebral palsy. Hypoxia is widely considered a mechanism responsible for fetal defecation and meconium-stained amniotic fluid; however, most fetuses with meconium-stained amniotic fluid do not have fetal acidemia. Intraamniotic infection/inflammation has emerged as an important factor in meconium-stained amniotic fluid in term and preterm gestations, as patients with these conditions have a higher rate of clinical chorioamnionitis and neonatal sepsis. The precise mechanisms linking intraamniotic inflammation to green-stained amniotic fluid have not been determined, but the effects of oxidative stress in heme catabolism have been implicated. Two randomized clinical trials suggest that antibiotic administration decreases the rate of clinical chorioamnionitis in patients with meconium-stained amniotic fluid. A serious complication of meconium-stained amniotic fluid is meconium aspiration syndrome. This condition develops in 5% of cases presenting with meconium-stained amniotic fluid and is a severe complication typical of term newborns. Meconium aspiration syndrome is attributed to the mechanical and chemical effects of aspirated meconium coupled with local and systemic fetal inflammation. Routine naso/oropharyngeal suctioning and tracheal intubation in cases of meconium-stained amniotic fluid have not been shown to be beneficial and are no longer recommended in obstetrical practice. A systematic review of randomized controlled trials suggested that amnioinfusion may decrease the rate of meconium aspiration syndrome. Histologic examination of the fetal membranes for meconium has been invoked in medical legal litigation to time the occurrence of fetal injury. However, inferences have been largely based on the results of in vitro experiments, and extrapolation of such findings to the clinical setting warrants caution. Fetal defecation throughout gestation appears to be a physiologic phenomenon based on ultrasound as well as in observations in animals.
绿色羊水，通常称为胎粪污染羊水，在 5%至 20%的分娩患者中存在，被认为是产科危险。这种情况归因于胎儿结肠内容物（胎粪）的通过，羊水内出血伴有血红素分解产物，或两者兼有。随着胎龄的增加，绿色羊水的频率增加，在过期妊娠中约为 27%。分娩时绿色羊水与胎儿酸中毒（脐动脉 pH<7.00）、新生儿呼吸窘迫和癫痫发作以及脑瘫有关。缺氧被广泛认为是胎儿排便和胎粪污染羊水的机制；然而，大多数胎粪污染羊水的胎儿没有胎儿酸中毒。宫内感染/炎症已成为足月和早产胎粪污染羊水的重要因素，因为这些情况下的患者临床绒毛膜羊膜炎和新生儿败血症的发生率更高。将宫内炎症与绿色羊水联系起来的确切机制尚未确定，但血红素分解代谢中的氧化应激作用已被牵连。两项随机临床试验表明，抗生素治疗可降低胎粪污染羊水患者的临床绒毛膜羊膜炎发生率。胎粪污染羊水的一个严重并发症是胎粪吸入综合征。这种情况在 5%的胎粪污染羊水病例中发生，是足月新生儿的一种严重并发症。胎粪吸入综合征归因于吸入胎粪的机械和化学作用，加上局部和全身胎儿炎症。在胎粪污染羊水的情况下，常规进行鼻/口咽抽吸和气管插管并没有显示出有益，并且不再推荐在产科实践中使用。一项随机对照试验的系统评价表明，羊膜内灌注可能会降低胎粪吸入综合征的发生率。对胎儿膜进行胎粪组织学检查已被用于医疗法律诉讼，以确定胎儿损伤的发生时间。然而，这些推论主要基于体外实验的结果，将这些发现外推到临床环境需要谨慎。基于超声以及动物观察，整个孕期胎儿排便似乎是一种生理现象。
