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????

Kids up to the age of 2 have numerous phases, which also includes their sleeping patterns. If your child is healthy and active, don't worry a lot and also make sure that she is eating well. My daughter also used to make up at 2-3 in the night when she was a year old, but she slowly got rid of that habit.