Pardi Giorgio, Marconi Anna Maria, Cetin Irene
Department of Obstetrics and Gynecology, DMCO San Paolo, University of Milano School of Medicine, via A. di Rudini' 8, 20142 Milano, Italy.
Placenta. 2002 Apr;23 Suppl A:S136-41. doi: 10.1053/plac.2002.0802.
The role of placental function in maintaining an adequate fetal growth has been addressed by many different laboratories. The relationship between maternal and fetal circulation in the placenta is crucial for efficient exchanges of oxygen and nutrients. Moreover, maturational changes are taking place throughout gestation within the placenta in order to increase the transfer capacities while fetal/placental weight ratio is significantly decreasing. In human pregnancies, an impairment in the invasion of fetal trophoblast cells into the maternal decidua has been hypothesized as a cause of placental insufficiency leading to intrauterine growth restriction (IUGR). This condition has been associated with a number of adaptive changes taking place in both placenta and fetus. Adaptive changes can be followed by pathology leading to fetal death and therefore staging of the disease is fundamental for timing of delivery.A classification of the severity of IUGR in human pregnancies has been proposed based upon fetal heart rate (FHR) and Doppler velocimetry of the umbilical artery (pulsatility index or PI). This classification of clinical severity reflects different degrees of placental insufficiency and is associated with significant differences in placental nutrient exchange. Only those IUGR with pathological PI and FHR are associated with increasing degrees of hypoxemia and lacticacidemia. Furthermore, significant differences are observed in the transplacental glucose gradient in the most severe cases and the placental transport of essential amino acids is significantly reduced both in vivo and in vitro. These findings suggest that both placental metabolism and transport are altered in intrauterine growth restriction in humans.
许多不同的实验室都研究了胎盘功能在维持胎儿充分生长方面的作用。胎盘内母体和胎儿循环之间的关系对于氧气和营养物质的有效交换至关重要。此外，在整个妊娠期，胎盘内都在发生成熟变化，以提高转运能力，而胎儿/胎盘重量比则显著下降。在人类妊娠中，有人推测胎儿滋养层细胞侵入母体蜕膜受损是导致胎盘功能不全进而引起宫内生长受限（IUGR）的原因。这种情况与胎盘和胎儿中发生的一些适应性变化有关。适应性变化之后可能会出现导致胎儿死亡的病理情况，因此疾病分期对于分娩时机至关重要。基于胎儿心率（FHR）和脐动脉多普勒测速（搏动指数或PI），有人提出了人类妊娠中IUGR严重程度的分类方法。这种临床严重程度分类反映了不同程度的胎盘功能不全，并与胎盘营养物质交换的显著差异相关。只有那些具有病理性PI和FHR的IUGR才与不同程度的低氧血症和乳酸血症相关。此外，在最严重的病例中，经胎盘葡萄糖梯度存在显著差异，并且必需氨基酸的胎盘转运在体内和体外均显著降低。这些发现表明，人类宫内生长受限会改变胎盘的代谢和转运。
