The phrase "prang up" is not commonly used in standard English. It seems there might be a misunderstanding or a mix-up with the word "impregnate." Let's clarify the word "impregnate" instead, which aligns with the definition you provided.
Impregnate (verb): To make someone pregnant.
While there are no specific idioms or phrasal verbs that directly relate to "impregnate," it can be part of discussions about family planning or reproductive health.
In summary, "impregnate" is a verb that means to make someone pregnant. It is used in formal contexts and can also refer to the process of fertilization in biology.