My daughter is of 1yr 9 months .... she doesn't sleep at night constantly. She sleep disturbed and always wakes up midnight.. I am very much tensed... Why this is happening????

are you sure she is not waking up due to any hunger pang? generally babies fall into a sleep pattern by the time they are about a year and a half at the most, but in some cases it may take a little more as well. i would suggest you let her have a good dinner where she gets full, and if possible, give her a glass of milk before she goes to bed. also, in case she wakes up in the middle of the night and tries to play, do not entertain her. instead, tell her to get back to sleep just as you are. she may take time to do so, but gradually will fall back to sleep. reduce the afternoon nap time a little if she sleeps in the day and see if it makes a difference.