Possessives and Attributives

Q. Which is correct: “so and so, four months pregnant” or “so and so, four months’ pregnant”?

A. Write “four months pregnant”—that is, without the apostrophe. The expression is analogous to expressions like “three hours late” and “five feet high.” In such cases, the expression of time or distance is simply modifying the adjective that follows. The apostrophe is reserved for the genitive case. The phrase “four months’ pregnancy” is an example of the genitive case because it can be rewritten with “of”: pregnancy of four months.