Keep in mind that "margin" means "edge", so marginal changes are adjustments around the edges of what you are doing.
“边际”就是“边缘”的意思，所以边际变动就是围绕你所做的事情的边缘调整。
2
The distance from the placental edge to the insertion of the umbilical cord was measured after delivery, and the results were used to classify cord insertion as normal, marginal, or velamentous.
分娩后测量脐带附着点到胎盘边缘的距离，将结果分为正常附着、边缘性附着和帆状附着。
3
Namely second is the marginal nature principle, select as far as possible at the edge of Central Plains like Xi 'an, Beijing and Nanjing etc ground as the capital.