There are three stages of pregnancy.
The first trimester which is 0-3 months
The second trimester 3-6 months
The third trimester 6-9 months.
The first trimester is the most crucial as this is the stage of pregnancy where any problems are at the highest risk.
The second trimester is said to be the best as its the "blooming" stage as side affects from the first trimester go away and you begin to enjoy pregnancy more.
The third trimester is said to be uncomfortable as your bump gets bigger you may find it hard to sleep and you get impatient as you cannot wait until you and your baby meet. you also feel like you need to Nest and get everything prepared for you and your baby.
I hope this helps