Nicole
There are a lot of other options besides the maya wrap. I had a maya wrap that I used for about the first 6 months but it has a huge learning curve and I much preferred my hotsling (its a pouch style sling, not a ring sling). Once Logan was about 3 months old I always carried him in the kangaroo carry in the maya wrap. In the hotsling I've always carried him on my hip (you can start that around 5 months old). When I have another baby I am going to try out a wrap and my friend makes ring slings so I may try one of her slings too - they're thinner fabric than the maya wrap. But I'm sure my main sling will still be my hotsling. I love them plus its better for business if I'm out and about in the sling I sell, LOL.
Tara - believe it or not, there is a whole website devoted to wearing twins. I've checked it out before and it is pretty cool. Just a bunch of articles and pictures on how to wear 2. But I think a lot of people wear 1 and push the other in the stroller, just alternating babies. I knew a girl w/ twins and that is what she did (whoever needed to be carried at the time was in the sling). Or both parents use slings and then both babies are worn at the same time. When they're newborns you can wear them in the same sling. Oh I saw a picture where a woman used a sling on each shoulder and wore both her babies (they were around 9 months old in the pic). But obviously if you have poor lung health then wearing them both when they're older is going to be tough.
