 Uterus is a big muscle and periodically you can have these contractions or spasms that occur. It is the timing, the frequency and the intensity of the contractions that will determine if labor will progress. Sometimes it's hard to tell whether what you're experiencing is a contraction or not. There's a few different ways that people can experience contractions. Some women feel a contraction feels like a period cramp. Sometimes people feel the contractions starting in their abdomen and wrapping to their back. Some people notice the contractions starts low in their back and wraps around to their abdomen. Additionally, contractions are usually rhythmic, so you'll have a contraction, it'll go away for five minutes, you'll have another contraction. When you're having contractions that are coming every five minutes for an entire hour and it's consistent during that hour, then you should start to come in. Now, if it's your second or your third baby, sometimes you might be further along when you hit those contractions every five minutes for an hour. So if it's your second or your third baby and you're starting to have contractions that are more intense and they're coming even every seven minutes for an hour, you should probably start to come in and get your cervix checked.