Perinatal Imaging and Health, Kings College London, London, UK.
Biomedical Engineering, Kings College London, London, UK.
NMR Biomed. 2021 Apr;34(4):e4475. doi: 10.1002/nbm.4475. Epub 2021 Jan 21.
Magnetic resonance imaging (MRI) in pregnancy is commonly undertaken in the left lateral tilt (LLT) position to prevent inferior vena cava (IVC) compression and supine hypotensive events, although this may be suboptimal for image quality. The supine position may also have an adverse effect on fetal well-being. The spinal venous plexus may provide an alternative pathway for venous return in the presence of IVC compression. This study assesses morphology and blood flow of the IVC and spinal venous plexus for pregnant women in LLT and supine positions to ascertain the effect of maternal position on venous return during MRI. Eighty-two pregnant women underwent phase contrast MRI (PC-MRI) of the IVC and spinal venous plexus in the supine position; 25 were also imaged in the LLT position. Differences in life monitoring, IVC, spinal venous plexus and total venous return between the two positions were assessed. A linear regression assessed the relationship between flow in the IVC and the spinal venous plexus in the supine position. Increasing gestational age and the right-sided position of the uterus on IVC and spinal venous plexus venous return were also evaluated. Hypotension symptoms were similar in supine (10%) and LLT (8%) positioning. Supine positioning decreased IVC height (p < 0.004) and flow (p = 0.045) but flow in the spinal venous plexus increased (p < 0.001) compared with the LLT position. Total venous return showed no difference (p = 0.989) between the two positions. Additional measurements of flow in the aorta also showed no significant difference between the two groups (p = 0.866). Reduced IVC flow in the supine position was associated with increasing gestational age (p = 0.004) and degree of right-sided uterine position (p = 0.004). Women in the left lateral decubitus position who then rotated supine had greater flow in the IVC (p = 0.008) and spinal venous plexus (p = 0.029) than those who started supine. For the majority of women, the spinal venous plexus acts as a complementary venous return system for pregnant women in the supine position, maintaining vascular homeostasis. Further study is needed to assess the effects on the health of the fetus.
磁共振成像（MRI）在妊娠期间通常采用左侧倾斜（LLT）位置进行，以防止下腔静脉（IVC）受压和仰卧位低血压事件，尽管这可能不利于图像质量。仰卧位也可能对胎儿健康产生不利影响。在 IVC 受压的情况下，脊柱静脉丛可能为静脉回流提供替代途径。本研究评估了 LLT 和仰卧位孕妇 IVC 和脊柱静脉丛的形态和血流，以确定母体位置对 MRI 期间静脉回流的影响。82 名孕妇接受了 IVC 和脊柱静脉丛的相位对比 MRI（PC-MRI）仰卧位检查；其中 25 名孕妇还进行了 LLT 位置成像。评估了两种位置之间的生命监测、IVC、脊柱静脉丛和总静脉回流的差异。线性回归评估了仰卧位时 IVC 和脊柱静脉丛之间的血流关系。还评估了 IVC 和脊柱静脉丛静脉回流中妊娠周数和子宫右侧位置的关系。仰卧位（10%）和 LLT（8%）定位时低血压症状相似。与 LLT 位置相比，仰卧位降低了 IVC 高度（p < 0.004）和流量（p = 0.045），但脊柱静脉丛的流量增加（p < 0.001）。两种位置之间总静脉回流无差异（p = 0.989）。主动脉额外流量测量也显示两组之间无显著差异（p = 0.866）。仰卧位 IVC 流量减少与妊娠周数增加（p = 0.004）和子宫右侧位置程度增加（p = 0.004）相关。从左侧卧位转为仰卧位的女性 IVC（p = 0.008）和脊柱静脉丛（p = 0.029）的流量大于从仰卧位开始的女性。对于大多数女性来说，脊柱静脉丛在仰卧位时为孕妇提供了一个补充的静脉回流系统，维持血管内环境稳定。需要进一步研究来评估其对胎儿健康的影响。
