Carbillon L, Challier J C, Alouini S, Uzan M, Uzan S
Department of Obstetrics and Gynecology, Assistance Publique, Hôpitaux de Paris, Jean Verdier Hospital, 93143 BONDY, France.
Placenta. 2001 Nov;22(10):795-9. doi: 10.1053/plac.2001.0732.
In the first weeks of pregnancy, columns of endovascular cytotrophoblastic plugs develop in the lumen of spiral arteries. Morphologic data show that these plugs become loosened as soon as the end of the second month and the intervillous circulation of maternal blood is likely to be established progressively between the 8th and 12th weeks. The disorganization of the musculo-elastic layers of these vessels provokes a dramatic decrease in vascular tone in the uteroplacental circulation. These modifications appear to govern the establishment of a low-pressure blood flow in the placenta, and hence determine the quality of uteroplacental circulation and normal fetal growth. Placental bed biopsies in women with pre-eclampsia and in a proportion of pregnancies with intrauterine growth retardation have shown that these physiologic changes were absent in the myometrial segments of spiral arteries. Recently, colour Doppler was used to assess intervillous and spiral artery flow in early pregnancy, confirming in vivo free intervillous flow at 12 weeks and a progressive significant decrease in spiral artery resistance with advancing gestation during the first trimester. However, certain data at an earlier gestational age are still contradictory. Particularly, the exact nature of the contents of the intervillous space before 8 weeks, and whether or not this fluid can be considered maternal blood, remains controversial.
在妊娠的最初几周，螺旋动脉管腔内会形成血管内细胞滋养层栓柱。形态学数据表明，这些栓柱在第二个月末就开始松解，母体血液的绒毛间隙循环可能在第8至12周之间逐渐建立。这些血管的肌弹性层紊乱会导致子宫胎盘循环中的血管张力急剧下降。这些变化似乎控制着胎盘内低压血流的建立，从而决定子宫胎盘循环的质量和胎儿的正常生长。对先兆子痫妇女以及一部分胎儿宫内生长受限的妊娠进行的胎盘床活检显示，螺旋动脉的肌层段不存在这些生理变化。最近，彩色多普勒被用于评估妊娠早期的绒毛间隙和螺旋动脉血流，证实了在12周时体内存在自由的绒毛间隙血流，并且在妊娠早期，随着孕周的增加，螺旋动脉阻力逐渐显著降低。然而，某些更早孕周的数据仍然相互矛盾。特别是，8周前绒毛间隙内容物的确切性质，以及这种液体是否可被视为母体血液，仍存在争议。
