big with child的意思就是“怀孕的”，“（孕妇）肚子大的”。它的起源可以追溯到中世纪英语。

【例句】
She is big with child and expecting her baby in a few months.
她怀孕了，几个月后就要生孩子了。

The actress was unable to continue filming because she was big with child.
这位女演员因为怀孕而无法继续拍摄。