Oh yeah, especially if you plan on more pregnancies. I have a few bins of clothes, and I just pull out whatever happens to fit at the time. We recently upped our life insurance, and the agent asked if I had lost or gained more than 10 lbs in the last year. I said, "That's not fair!" And then he looked at the paper again and said, "Oh, not due to pregnancy."
Those 10 (to 60) pound weight gains and loses every other year for the last 7 have made me pretty grateful for my stash. :)
(But, I do find that when I get around to those clothes again, I still wind up giving a lot away because they are dated or I just don't like them or whatever. And, loosing all the weight, and then some, doesn't necessarily mean that things will be arranged the same way.)