Department of Obstetrics and Gynecology, Medical University of Graz, Graz, Austria
Diabetes Care. 2018 Jul;41(7):1362-1369. doi: 10.2337/dci17-0045.
The placenta plays a key role in sustaining fetal growth and development. Due to its position between mother and fetus, it is exposed to changes in the intrauterine environment in both circulations. The relative influence of changes in those circulations depends on the period of gestation. Early in pregnancy, maternal influences prevail and may affect the complex biological processes characteristic for this pregnancy period, such as placentation, early cell differentiation, and spiral artery remodeling. It is still unclear whether the placenta early in pregnancy is a friend or foe for the fetus. Later in pregnancy, when the fetal circulation is gradually establishing, fetal signals gain importance in regulating placental structure and function. Many of the placental alterations seen at term of pregnancy are the result of fetoplacental interactions often driven by fetal signals associated with maternal diabetes or obesity. These alterations, such as hypervascularization or enhanced cholesterol removal from placental endothelial cells, can be regarded as adaptations to maintain homeostasis at the fetoplacental interface and, thus, to protect the fetus. However, extreme conditions such as poorly controlled diabetes or pronounced obesity may exceed placental homeostatic capacity, with potentially adverse consequences for the fetus. Thus, in late pregnancy, the placenta acts mostly as a friend as long as the environmental perturbations do not exceed placental capacity for mounting adaptive responses.
胎盘在维持胎儿生长和发育方面起着关键作用。由于它位于母亲和胎儿之间，因此在两个循环中都暴露于宫内环境的变化。这些循环变化的相对影响取决于妊娠的时期。在妊娠早期，母体的影响占主导地位，可能会影响到胎盘形成、早期细胞分化和螺旋动脉重塑等这一妊娠阶段的复杂生物学过程。目前尚不清楚妊娠早期的胎盘对胎儿是敌是友。在妊娠后期，当胎儿循环逐渐建立时，胎儿信号在调节胎盘结构和功能方面变得重要。许多在妊娠晚期出现的胎盘改变是胎儿信号与母体糖尿病或肥胖相关的结果，常导致胎-胎盘相互作用。这些改变，如血管增生或增强胎盘内皮细胞中的胆固醇清除，可以被视为维持胎-胎盘界面内环境稳定的适应，从而保护胎儿。然而，极端情况，如控制不佳的糖尿病或明显肥胖，可能超过胎盘的稳态能力，对胎儿产生潜在的不利影响。因此，在妊娠后期，只要环境干扰不超过胎盘适应反应的能力，胎盘主要是作为胎儿的朋友。
