Many of the cloth nappies sold nowadays are called "Birth-to-Potty", "One-Size" or "One Size Fits Most". These generally fit from about 4kg right though to potty training (on all but the chunkiest of toddlers or children who potty train late). However, they don't fit newborn babies at all well, even big newborns, because new babies are so tiny and their legs are so skinny. You can buy newborn sized nappies but these may only fit for a few weeks if your baby grows fast and so can work out very expensive.
One solution to this problem is to just use disposable nappies (preferably eco-disposables) for the first month or two until your baby is big enough for Birth-to-Potty nappies. Relax, get to know your baby, get feeding well-established and then think about saving the planet and using cloth nappies.
A second solution is to borrow or hire a set of tiny nappies. The Nappy Shed has some sets of 30 or so very small nappies, of a mix of different styles, that can be hired for £50 for 6 weeks. You'll find them in the Shop section of this website. They do tend to get booked out months in advance so email me ([email protected]) to check if they are available for when you want them. Alternatively there may be a nappy library located near you who can lend you some tiny nappies. http://www.uknappynetwork.org/find-a-library.html
A third solution is to just buy some tiny nappies of your choice and to hell with the cost. If you plan to have several children, or can pass the nappies on to a relative or a friend, this isn't such a daft idea. Some special newborn nappies (such as Close Pop-in Newborn, Li'l Joey Newborn and TotsBots Teenyfits) are really very small and will only fit for a few weeks - nice for premature or especially small babies - other brands last for the first few months. Baba+Boo Newborn nappies are lovely little pocket nappies that will fit from birth for 4-5 months. They have an extra row of elastics inside to catch explosive milky poo. If you fancy a two-part nappy, with separate wrap, TotsBots Bamboozles and Peenut wraps in size 1 fit a new baby and Easy-Peasy nappies come in a newborn size. Tjs Cloth Nappies sell good quality tiny wraps at a very reasonable price
A fourth solution is to buy some very cheap and simple old school flat nappies, some Nappi Nippas to fasten them, some tiny waterproof covers (=wraps) to go on top, and then learn how to fold them. It's not very difficult and the nappies are surprisingly effective. If you are only planning to use these nappies for a few weeks, you don't want anything too thick or too big - muslin nappies or size 1 prefolds are probably best. When I had babies (back in the Dark Ages when all babies wore cloth nappies) we used to use the same thick, fluffy, full-sized terry towelling nappies on our babies from day 1 right through to age 2-3 years. (The midwife showed you how to fold them before you left hospital.) The nappy completely covered a newborn baby from armpits to knees and it was quite a hilarious look. I don't think many mums would be happy with this nowadays!
Here's a bit of help with terminology. There are 3 main types of flat nappies.
(1) Terry squares. These are traditional British nappies made of squares of fluffy terry towelling - your mum may have used these on you. They are normally made of 100% cotton but bamboo+cotton mix are also available. They are usually 60cm square but you can get 50cm for little babies and 70cm for toddlers. Beware of getting anything too thick if you want to use it on a new baby as it will be hard to fasten neatly and will make their bum look huge.
(2) Muslin squares. These are 70cm squares of thin cotton fabric (muslin) - so thin that you can just about see through it when you hold it up to the light. These are mainly used as burp cloths and general mopping cloths and are only absorbent enough to work as nappies on tiny babies - but they can see you through the first few weeks. You can use two at once if you need more absorbency, or add a bamboo booster in the wettest area at the front and between the legs. Muslin squares are used a lot in other parts of the world but they are generally bigger than our muslin squares and so can be used on bigger babies. They're ideal for a hot climate. There are various ways of using a muslin nappies and I've shown a few below.
(3) Prefolds. These are huge squares of muslin or similar thin cotton fabric that have been folded (hence the name) and stitched to make a smaller square or rectangle. There's a strip down the middle that's 3-4 layers thick but the sides are just 2 layers thick. They come in 2 sizes - size 1 for use from birth to about 6 months and size 2 for bigger babies. Bambino MioDuo (which used to be called Bambino MioSoft) are prefolds. (Not to be confused with Bambino MioSolo all-in-one nappies).