How long should I wait after giving birth to revamp my wardrobe? How long should I save pre-pregnancy clothes in case they fit again someday?
I hate to break it to you, but this is a multi-step process. When you first come home from the hospital, you'll probably be the most comfortable wearing sweatpants and maybe some maternity clothes. For the first couple of weeks, you may even be willing to wear maternity clothes. Then, if you and I have anything in common, you'll start to feel all droopy, both visually and emotionally. You'll get antsy to get out of the house, and you'll want to wear something different from what you've been wearing for the past nine months.
These are signs that you're ready for phase 1: the maternity leave wardrobe. These items should be inexpensive and durable, and they should fit your body, now, even if the size on the tag makes you cringe. It doesn't matter. It's time to wear pants with a zipper and shirts that are the same length in the front and the back. Don't form any lasting attachments with these clothes, as they are likely to get stained immediately with all manner of bodily fluids, and hopefully because you'll outgrow them quickly (with "outgrow" meaning to lose the baby weight so fast your friends forget you were ever pregnant, except for the baby who hangs around with you now). These clothes should make you feel like a respectable adult and someone you wouldn't be embarrased to see reflected in a window. Light colors hide spit-up better, but, if you're nursing, dark colors hide leakage. Buy enough clothes that you'll be able to get dressed for a few days in a row without having to do laundry, but not so much that you'll kick yourself when they stop fitting or get ruined.
When your leave is over, it's time for phase 2: the back-to-work wardrobe. These items have many things in common with the above (durability, cost, fit), but they need to reflect your current professional responsibilities and your career aspirations. They should scream "put together" because, regardless of where you work, "put together" is always appropriate, and you'll need something that distracts people from the dazed look in your eyes at being expected to carry on adult conversation for the first time in weeks (or months, if you're lucky to have had that much time off). These are clothes that you're going to put on right before you leave the house and take off right when you come home, preferably before a baby has the chance to touch you. You need fewer of these, but you have to take good care of them. They should also be neutral and interchangable so your co-workers don't catch on to how small your current wardrobe rotation really is. This is also a good time to see what pre-pregnancy clothes you can still wear. If the answer is, "none," don't despair.
Someone coined the phrase, "nine months up, nine months down," meaning that when your baby is nine months old, your body has probably bounced back as much as it's going to without some serious intervention. Nine months (ten, if you want to be generous, twelve if you're really optimistic) is a good time to enter into phase 3: the rest of your life. Take a serious look at your wardrobe, assess what you actually want to wear, what's still in good condition and what's still fashionable. Have a clothes swap, take a trip to Goodwill, burn them, do whatever you need to do to move on, but get rid of things that are never going to work for you again. Feel free to save a few novelty items, but move them to storage instead of keeping them in your closet. Look objctively at what items you still have, what outfits you can make from them and what's missing for what you want to wear at home, with friends and at work. Then go out for a shopping trip that addresses those particular needs, respects your new shape and fits with your lifestyle. And, if you want to have more than one kid, be prepared to start from scratch the next time around.