Sometime during your second or third trimester, you might start to feel mild, sporadic contractions, especially when you are tired or dehydrated, or after sex. These normal contractions, called Braxton Hicks contractions or false labor, are your body's way of rehearsing for birth. Think of them as a kind of warm-up for true labor. Braxton Hicks contractions feel like a tightening of your abdomen, something like a sit-up. They are usually mild and painless. Other times it can be more painful. You might worry you are going into true labor, but these early contractions don't happen at regular intervals and they don't dilate your cervix.
As you get closer to your delivery, Braxton Hicks contractions may intensify.