Hi,
Yes, one of the most noticeable signs of perimenopause are irregular cycles. Periods can either become closer together or farther apart; sometimes lighter or heavier. In regard to fertility, it begins to naturally decline the older we get, so by our late 30's/early 40's it declines more rapidly until it ceases. During perimenopause our hormone levels (Estrogen, Progesterone, and Testosterone) decrease, and ovulation slowly begins to come to an end...
If you're interested in becoming pregnant, my advice would be to start keeping track of your ovulation and menstrual cycles now. Also consult your Ob/Gyn if you have any concerns. The healthier and better shape you're in will definitely influence any possible pregnancy and transition into menopause... Take Care