Yeah, but in general it's not enough to impact having 2 kids. If getting pregnant for the first time at 30, you could wait the recommended 18 months between kids and still have two without it being a geriatric pregnancy. You don't need to start at 18 to have 2 kids.
That's not how pregnancy works. It can take quite a while to get pregnant. it's a bell curve. Certainly, a lot of couples will have another, but if you want to have another with a good chance of success (>90%), you have to start younger.
