Re: Weight gain / sleeping through the night
My two cents? Your daughter's weight is fine. My son was born average size, and has dropped weight percentiles along the way (see my signature). My pediatrician has declared him a very healthy, strong baby (with two fairly thin parents). I don't think a baby must stay on the same curve throughout infancy, and 20th to 13th doesn't seem very dramatic a drop....Does your daughter seem healthy to you? Does she have a lot of wet diapers?
I don't think spacing feedings will get her more milk - if anything, she would eat less milk overall. She is very young yet - if she's hungry every 1.5-2 hours, that seems normal.
In regards to sleeping through the night, I would let her sleep if she's not waking. If she's really hungry, she'll let you know. And her sleeping through the night is likely not permanent. That said, if you are worried about her weight gain, I bet if you feed her in the night she will eat. I was very worried about my son's weight gain around 4-5 months, so every time he would move or smack his lips in his sleep, I would feed him. It seemed like every hour. It was awful - I do not recommend it. So really, if she's not going to wake, I would not feed/wake her.
DS October 2010
0 days: 7lbs6oz, 20"
4 days: 6lbs8oz
2 months: 11lbs4oz, 22.75"
4 months: 13lbs5oz, 25"
6 months: 14lbs14oz, 26.5"
9 months: 16lbs13oz, 27.75"