My 10month old baby will comfort herself to sleep by sucking on the back of her left hand. If i push her hand away, she will wake up / gets angry and all effort to make her sleep will have to restart all over again. How to get her to stop this habit of sucking her hand to sleep?

My 4 month old self soothe herself to sleep by sucking her fingers as well. I try to get her to sleep by putting a comforter next to her but she still ends up sucking her fingers. I don't think there's anything wrong with our babies sucking their fingers to sleep - when they are awake, perhaps always tell them not to suck their fingers so they won't make it into a habit. FUN FACTS: I noticed girls tend to suck fingers more than boys. My boys never did suck their fingers. I wondered why...