Corpus luteum in pregnancy has a long life. However, if fertilisation does not take place it remains active only for 10-12 days . Why?

This is because of a neural signal given by the maternal endometrium to its hypothalamus in presence of a zygote to sustain the gonadotropin (LH) secretion, so as to maintain the corpus luteum as long as the embryo
remains there. In the absence of a zygote, therefore, the corpus luteum can not be maintained longer.