Preterm Labor Symptoms

When labor occurs between 20 and 37 weeks of pregnancy, it’s called preterm labor. Being in labor means that the cervix is opening and can result in preterm birth. Babies born premature are at risk of health complications and may require extensive support in the Neonatal Intensive Care Unit (NICU). Sometimes, the signs of preterm labor are clear (like your water breaking), and other times preterm labor symptoms are more ambiguous. With prompt medical intervention, preterm labor can sometimes be slowed or stopped entirely with medications, cervical cerclage, and/or bed rest. Read on to learn the signs and symptoms of preterm labor. 

Signs and Symptoms of Preterm Labor

Rupture of Membranes

The most obvious sign of labor commencing is when the amniotic sac breaks suddenly. When this happens before week 37 of pregnancy, it’s referred to as Preterm Premature Rupture of Membranes (PPROM). A gush of clear fluid from the vagina is a telltale sign that labor is on its way. Amniotic fluid can also be tinged green if the baby has passed meconium. Though the most obvious sign of impending preterm labor is PPROM, it is not the most common. 

Sometimes, the amniotic sac can break but not cause a big gush. For example the sac can tear higher up in the womb, causing a slow leak. However, since premature babies are smaller and their heads are not yet engaged in the pelvis, most women experiencing PPROM notice a steady gush of fluid. Any substantial leaking of fluid from the vagina warrants an immediate call to your care provider. 


Contractions are a tightening of the uterine muscles. Contractions before 37 weeks can be normal, as in Braxton-Hicks contractions that do not cause the cervix to dilate or efface. Braxton-Hicks contractions are typically mild, infrequent, and may come and go as you change positions. On the other hand, contractions that are painful or frequent are a sign of preterm labor. Call your provider if you experience 4 or more contractions in an hour. 


Another symptom of preterm labor is a dull low backache. As the cervix moves and opens in preparation for labor, many women experience this early labor symptom. The pain might be constant or come and go. 

Backache in pregnancy is common and is most often normal. However, if you experience a near-constant low backache that cannot be relieved by comfort measures such as stretching, massage, or a heating pad, call your provider. They may have you come in to ensure your cervix is not opening. 

Vaginal Discharge

An increase in vaginal discharge in pregnancy is common. However, a substantial increase in vaginal discharge can be a symptom of preterm labor. Discharge that is watery, contains mucous, or is blood-tinged (pink, red, or brown) warrants a prompt call to your doctor or midwife. This may indicate leaking amniotic fluid or beginning to lose your mucous plug. 

As always, call your provider if you experience any outright vaginal bleeding in pregnancy. Bright red bleeding like a period is a sign of medical emergency such as placental or uterine abruption.

Other Preterm Labor Symptoms

Contractions, backache, and changes in vaginal discharge are the most telltale signs of preterm labor. However, it’s important to look out for less obvious signs as well, such as:

  •  Flu-like symptoms, such as nausea, vomiting, or diarrhea
  • Increased pressure in pelvis or lower abdomen 
  • Menstrual-like cramps

If you experience just one preterm labor symptom, call your provider. Time is of the essence in stopping or slowing preterm labor. Do not worry if it turns out to be a false alarm; it’s better to be cautious and proactive.