What it means
ということは presents a preceding fact, statement, or situation as the basis for an inference. It means “that means” or “so that implies,” and it is normally followed by the conclusion that can be drawn from the preceding information. The conclusion may be certain, probable, or presented as a question, depending on the context. The phrase can also introduce a restatement of what the preceding information amounts to.
Usage note
ということは usually connects an earlier proposition to an interpretation or conclusion, so it commonly appears before a comma and a following clause. Do not confuse it with ということだ, which can state or conclude that something is the case without the same topic-and-inference focus.
How to use it
彼が参加しないということは、計画を見直す必要があります。
The fact that he will not participate means that we need to review the plan.
彼が参加しないということは、計画を見直す必要がある。
The fact that he will not participate means that we need to review the plan.