Mothers have been warned for years that sleeping with their newborn infant is a bad idea, because it increases the risk that the baby might die unexpectedly during the night.
2016年6月六級真題（第一套）聽力 Section B
柯林斯高階英漢雙解學習詞典釋義
ADJ-GRADED
想不到的；未預料到的；意外的
If an event or someone's behaviour is unexpected, it surprises you because you did not think that it was likely to happen.