Lines 316-329 infer Danforth's reason for telling proctor that his wife is pregnant in response to proctors claim that Mary will admit to lying to the court

This line is from a book called The Crucible which is a 1953 play by an American playwright Arthur Miller. It is a staged and partly fictionalized story of the Salem witch trials which happened in the Massachusetts Bay Colony during 1692-93.

And the Danforth informed Proctor that his wife is pregnant is that they will be hanged after she gives birth to her baby, so she will have some time to prove to them that she is not guilty.