Passing down kids underwear??

Amanda
Those of you with older kids (esp 2 or more)  have you pasted down/ held on to underwear? 
I'm 7 weeks pregnant with #2. My 1st is 3.5 and just growing out of her 2t/3t underwear. I'll all about hand me downs in general, but torn when it comes to underwear. I'm cleaning out her underwear drawer today ;) 
They are in good condition. Our washing machine has a steam function, so I could steam clean them if we have another girl. Thoughts??