Let's see, I had 7 4oz bottles, then I lost one so it was 6. I washed all the bottles every night and refilled them. (I make a day's worth of formula at one time.) Of course, now DS is taking 5.5oz @ a time so we're using 8oz bottles now. I have about 10 of those, though you really don't need that many. I think I actually wish I had less. I let the bottles go longer w/out washing having that many, but on the up side, I can make 48 hours worth of formula at once. (DON'T do that w/ powder, ONLY liquid RTF or concentrate. Powder is only good for 24 hours once prepared.) You shouldn't need 9oz. bottles, 8oz is plenty big. I haven't heard anyone recommend a baby be given more than 8oz of formula at a time anyway. So, if you're going to wash your bottles EVERY night, 6 - 8 of each size ought to be plenty. (I use Dr. Brown's bottles, so I also have a handful of inexpensive bottles for going out that I won't mind if I lose.)
A newborn eats about 8-10 times in a 24 hour period. An older infant (2-4 months old) eats 5-6 times. You can put the bottles in the dishwasher or hand wash them, but hand-washing all of them is a pain when you're sleep-deprived and have all those bottles to wash EVERY DAY. I bought a dishwasher container for the nipples and rings which keeps them in place. I have 12 smaller bottles (I keep one in the diaper bag) so I can have a day's worth of formula made and just grab the bottles as I need them. I put that day's "set" in the dishwasher (I have to run it every night whether or not it's full) and pour the ones for the next day without having to worry about waiting for the dishwasher. DD2 never made it past 6 ounces per feeding, so I never needed the larger size bottles for her. DS is just over 3 months and will be moving up to 8 ounces in the next week or so since he's consistently starting to take in 6 ounces per feeding. I have 9 of those bottles. He doesn't eat over 6 ounces at every feeding, so I should be able to get away with 9 plus a couple of the smaller bottles for the evening cluster feedings when he only eats 2-4 ounces. Once they start on solid foods (our dr. says 4 months) they take in less formula per feeding and go down to 3-4 bottles per day, so you probably won't need the larger bottles for very long, if at all. You may want to wait on those.
I use the powder formula and make a day's worth of formula in a 1 quart container, because the powder (Isomil) sometimes clumps, but after it's refridgerated for a while the clumps finally dissolve. I pour it into bottles, especially for the overnight feedings so I can get one ready quickly. I heat it by putting it in a glass in the sink and running hot water over it for a few minutes while I change DS's diaper. That way it's ready when he's ready to eat.
Sorry, I just re-read your post and realized that you're considering 4 oz bottles. I have Evenflo Comfi' bottles and the smaller ones hold 6 ounces. DS has been taking 4-6 ounces consistently since he was about a month old, so if you're contemplating 4 oz and 9 oz bottles you'll need the larger ones earlier so you'll probably want a few more of those too. If you go with 6 oz bottles, you may not need the larger size or as many of them.
jmcummins-Thanks so much! All this info is so helpful. I am planning on using Avent bottles and they come in 4oz and 9 oz sizes so it looks like I will need both because the 4oz won't be big enough as she gets bigger and drinks more. Thanks again for your help!
*Angel Baby July '05
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My sister uses Avent. My grandma THOUGHT she was getting her small bottles and big bottles, but really she got big bottles and BIGGER bottles. Avent has 4oz, 9oz, and 11oz. WHY do they make 11oz baby bottles? Anyway, my grandma gave my sister 9oz and 11oz bottles instead of 4oz and 9oz, LOL.
Here's my first advice - If I had to do it all over again, this is what I would do. Don't plan on buying a lot of any one bottle. Bottles and nipples are different and you never know what your dd is going to like and not like. And trust me, she will have a preference.
This is all fresh in my head since I just packed up dd bottles (she turns 1 on Sat). I remember I had 4 different sets of bottles. All of which we used after she was nursed. But she still refused 3 of the 4 types of bottles. Since then, we've stuck to one and only keep 3 in rotation. And it's a 9oz size. We hand wash our bottles after every use - just something we are used to doing.
Anyway, my point is wait to buy the bigger size bottles until you know which brand she's going to take.
Also, you can actually squeeze another ounce into the bottles anyway if you fill all the way up. I started with the 4oz size and it wasn't until 5 months that we moved up to the 9oz size.
Good luck, I know it's overwhelming trying to figure all of this stuff out. But one thing I found out (of course the hard way) is that it all has a way of working itself out.
I didn't have the problems Trooper did with baby refusing a particular type of bottle since I used the Dr. Browns bottles (a little extra to wash, but worth it).
I had 8-4 oz. bottles that we used until she started to drink more than that at a time (about 5 months), then we switched to the 8 oz. bottles. I bought those off of an online auction site for half the price and purchased new nipples.
We make up 5-6oz. bottles a day (in advance) and it's nice having a few extras in case baby is extra hungry one day or in case we want to give her pedialyte or water separate from the formula (especially useful when she's sick).