The hardest part of tandem for me in the first few months was realizing how much fluid I had to DRINK. I'd drink what seemed like gallons of water and still only go pee about 3 times a day (which stood in such shocking comparison to late pregnancy). Eating too, I've heard it can be 1000 calories a day in milk, so make sure you are getting plenty of good food. For me getting enough fat in my diet was really important for how well I felt, although I admit sometimes the fat came in the form of ben and jerry's.
And you 9 mo old may let up a bit in a few weeks, my DS who was 20 mo when I had DD nursed with his sister at almost every feeding the first few weeks, just the newness of it all, and all the plentiful milk, but after a bit he reduced his amount. I'm curious to see the difference tandem nursing this time with my 2.5 year old and a newborn, I kind of hope she doesn't go too nuts with nursing all the time.
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