The antonyms for "becomes pregnant" could be "remains infertile", "avoids conception", "prevents pregnancy", or "endures sterility". These phrases suggest a lack of ability or desire to conceive and carry a child to term. Some additional antonyms could include "undergoes menopause", "has a hysterectomy", or "terminates a pregnancy". However, it is important to acknowledge that not all individuals have the choice or ability to become pregnant, and the language used should be respectful and sensitive to this fact. Additionally, the decision to become pregnant is deeply personal and should be respected regardless of an individual's choice.