The strict technical definition of preterm labor is when a woman begins to have contractions and changes in her cervix before she’s 37 weeks along. Many women have contractions but no cervical change — in which case it isn’t real preterm labor. However, in order to find out whether your cervix is changing, you need to be examined.
In addition, your practitioner determines how often you’re contracting by placing you on a uterine contraction monitor (like the one used to perform a non-stress test).
The contractions associated with preterm labor are regular, persistent, and often uncomfortable. They usually start out feeling like bad menstrual cramps. (Braxton-Hicks contractions, in contrast, aren’t regular or persistent, and they usually aren’t uncomfortable.)
Preterm labor may also be associated with increased mucous discharge, bleeding, or leakage of amniotic fluid. Diagnosing preterm labor as early as possible is important. Medications aimed at arresting premature labor work best if the cervix is dilated less than 3 centimeters. If labor occurs after 35 weeks, your practitioner probably won’t try to stop your contractions except in rare circumstances (such as poorly controlled diabetes).
If you find that you’re having regular, uncomfortable, persistent contractions (more than five or six in an hour) and you’re not yet 35 to 36 weeks pregnant, call your practitioner. The only way to tell whether you’re experiencing real preterm labor is to be examined. Also, if you think your membranes have ruptured (your water has broken) or if you’re having any bleeding, call your practitioner right away.