It also causes a decline, because later pregnancies will also mean fewer children. Pregnancies after 35 are called "geriatric". (Actually, they now call it "advanced maternal age" to sound less insulting, but the older term conveys how much harder it is to get pregnant and fully gestate.)
A woman who waits until 30 to start a family is likely to not have one. It's a deeply unfortunate dilemma, because her male partner suffers much less decline.
Your anecdote suggests pushing out the population but not causing it to decline.