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Related & look-alikes

Labor & postpartum Medical emergency

Preterm labor

Also known as Premature labor, Preterm birth. Between 20 and 37 weeks.

Preterm labor begins too early, when regular contractions start to open the cervix before 37 weeks. It matters because a baby born this soon still has developing organs, the lungs above all. The early signs feel like ordinary pregnancy aches, and you cannot tell at home whether contractions will progress, so the message is simple: learn the warning signs, and if you have them, be seen right away. Even a little time gained can change your baby's outcome.

Know the warning signs When to call a provider
How common
About 1 in 10 US births
Around 10%, with significant racial disparities.
When
Before 37 weeks
From 20 weeks up to 37 weeks.
Urgency
Emergency
Regular contractions or leaking fluid before 37 weeks means go in now.
Outlook
Better with every day gained
Delaying birth even 48 hours lets steroids protect the lungs.

This can be a medical emergency. Regular or frequent contractions or belly tightening, such as four or more in an hour, before 37 weeks If this happens, go to the ER or call 911 right away.

Understanding it

What is preterm labor?

Preterm labor is regular contractions that make the cervix change, soften, thin, or open, before 37 weeks; a birth before then is a preterm birth. About 1 in 10 US babies is born preterm, and not evenly: preterm birth is roughly 50% more common among Black women than among white or Hispanic women, a gap driven by social and structural factors, not anything individual.

Prematurity matters because a baby's organs finish maturing in the last weeks. The lungs especially may not be ready to breathe air, and preterm babies face higher risks of breathing trouble, feeding and temperature problems, and infection, plus, the earlier they arrive, longer-term developmental challenges.

And time helps. Slowing labor even 48 hours opens a window to give steroids that speed your baby's lung development, medicine to protect the brain when birth is very early, and, if needed, to move you to a hospital with a newborn intensive care unit. Those steps improve how preterm babies breathe and survive.

Not every bout of contractions is true labor, and most people with warning signs do not deliver right away. But you cannot know that at home, so the safe move is to call and be checked.

Symptoms

What are the symptoms?

The milder signs mimic ordinary pregnancy discomfort, which is why they are worth knowing. Regular contractions or leaking fluid before 37 weeks means going in now.

Early signs

  • A low, dull backache
  • Pelvic or lower-belly pressure, as if the baby is pushing down
  • Mild belly cramps, sometimes with diarrhea
  • A change in vaginal discharge, or more than usual
  • Menstrual-like cramping

Emergency signs — call 911

  • Regular or frequent contractions or belly tightening, such as four or more in an hour, before 37 weeks
  • A gush or steady trickle of fluid, which can mean your water has broken
  • Vaginal bleeding or spotting
  • Constant pelvic pressure or pain that does not ease when you change position
  • Any sense that something is wrong; when in doubt, go in

Why it matters

Risks to you and baby

Immature lungs and breathing problems

A baby's lungs are among the last organs to mature, so preterm babies often need help breathing. That is why steroids to speed lung development are so central to care.

Other newborn complications

Preterm babies can struggle to feed, stay warm, and fight infection, and may need time in a newborn intensive care unit. The earlier the birth, the greater these risks.

Longer-term challenges

Babies born very early face higher risks of developmental, learning, and sometimes neurologic conditions such as cerebral palsy. Magnesium sulfate before a very early birth helps protect the brain.

Preterm rupture of membranes

Sometimes the water breaks before labor and before term, called PPROM. It needs prompt evaluation, because it raises the risk of infection and of an early delivery.

Why gaining time matters

Delaying birth even 48 hours lets steroids work and, if needed, allows transfer to a hospital with a NICU, among the most effective steps possible for a preterm baby.

How it's found

How is it diagnosed?

Diagnosis combines a cervical exam, a cervical ultrasound, and sometimes a swab, along with monitoring your contractions and checking whether your water has broken.

Cervical exam

Whether the cervix has begun to open or thin, the change that separates true labor from contractions that are not yet moving it.

Transvaginal cervical length ultrasound

The length of the cervix. Short points to higher risk; a normal length is reassuring.

Fetal fibronectin swab

A vaginal swab whose value is mostly in a negative result: if negative, you are very unlikely to deliver within a week, which can spare unnecessary treatment.

Contraction and membrane check

Monitoring records how frequent and strong contractions are; an exam checks whether the membranes have ruptured or infection is brewing.

When you have contractions or warning signs before 37 weeks. Prompt evaluation is what lets time-sensitive treatments start.

Treatment

How is it managed?

Treatment aims to buy time for steroids to work, protect your baby's brain if birth is very early, and get you to a hospital equipped for a preterm baby.

Treatment paths

Medicines called tocolytics can often delay birth by about 48 hours. That window buys time for corticosteroids to speed lung development, magnesium sulfate to protect the brain when birth is expected before 32 weeks, antibiotics for group B strep if indicated, and, when possible, transfer to a hospital with a newborn intensive care unit.

Medication

Tocolytics such as nifedipine or indomethacin delay birth briefly. Corticosteroids are given for lung maturity, generally between about 24 and 34 weeks, and magnesium sulfate for brain protection before 32 weeks.

Monitoring

Your contractions, cervical change, and your baby's wellbeing are watched closely to guide whether labor can be safely delayed or should proceed.

Can it recur?

A prior preterm birth is the strongest risk factor for another, with a recurrence of roughly 30%. If you have had one or have a short cervix, vaginal progesterone and, in selected cases, a cervical stitch (cerclage) lower the risk, and your cervix can be measured by ultrasound in a future pregnancy to catch shortening early.

What you can do

Can it be prevented?

  • If you have had a preterm birth or short cervix, ask about progesterone

    For those at higher risk, vaginal progesterone and cervical-length monitoring can lower the chance of another preterm birth. Raise it early in your next pregnancy.

  • Cervical cerclage when appropriate

    For selected people with a short cervix and a history of preterm birth, a stitch reinforcing the cervix, placed before 24 weeks, can help.

  • General steps that help

    Start prenatal care early, treat infections promptly, do not smoke, and space pregnancies at least 18 months apart when you can. These lower the baseline risk.

Who is more at risk

Risk factors

A previous preterm birth
The single strongest predictor of another.
Recurrence of about 30%
A short cervix
A cervix that is short or shortens early raises the risk and can be watched by ultrasound.
Carrying multiples
Twins or more stretch the uterus and commonly lead to earlier delivery.
Infection
Urinary, vaginal, and uterine infections can trigger preterm labor, which is why they are treated promptly.
Smoking and short pregnancy spacing
Smoking, substance use, and a short interval between pregnancies all increase risk. Black race is an independent risk factor too, reflecting structural and social inequities, not biology.

Do not wait

When to call your provider or 911

  • Go to labor and delivery right away for regular or frequent contractions before 37 weeks, such as four or more in an hour.
  • Go in immediately for a gush or steady trickle of fluid, which can mean your water has broken.
  • Seek care now for vaginal bleeding, or constant pelvic pressure or cramping that does not ease with rest or a change of position.
  • Call for a change in discharge, a persistent low backache, or simply a sense that something is off; it is always okay to be checked.
  • If you are higher risk, a prior preterm birth or short cervix, keep a low threshold to call, and ask what plan is in place.

Talking to your team

Questions to ask your provider

  • Am I actually in preterm labor, or are these contractions not yet changing my cervix?
  • Can my labor be safely delayed, and should I get steroids for my baby's lungs?
  • Do I need magnesium sulfate to protect my baby's brain?
  • Is this hospital equipped to care for a baby born this early, or should I transfer?
  • If I have had a preterm birth before, should I be on vaginal progesterone or have my cervix measured?
  • What signs mean I should come back immediately?

Keep reading

More on preterm labor

All pregnancy guides articles

Good to Know

Preterm labor FAQs

Common questions about preterm labor, answered.

How do I know if these contractions are real preterm labor or just Braxton Hicks?

You often cannot tell at home, and that is the point. Braxton Hicks are usually irregular and ease with rest or fluids. Contractions that are regular, frequent (four or more an hour), or come with pressure, cramping, fluid, or bleeding before 37 weeks need checking in person.

What counts as too early?

Any birth before 37 completed weeks. The earlier it is, the more support a baby needs, which is why every week, even every day, gained matters.

Can they stop my labor?

Sometimes it can be slowed with medicines called tocolytics, usually for about 48 hours. That may not stop the birth, but it buys crucial time for steroids and, if needed, a move to a hospital with a NICU.

Why do I need steroid shots?

Corticosteroids speed your baby's lung development and lower the risk of serious breathing problems and other complications of prematurity. They are among the most effective treatments when preterm birth is likely, generally used between about 24 and 34 weeks.

My water broke early. What happens now?

When the water breaks before term (PPROM), you need prompt evaluation. Care may include antibiotics, steroids, and monitoring, because early rupture raises the risk of infection and delivery. Go in right away.

Will my baby be okay?

It depends heavily on how early the birth is. Late preterm babies often do very well; very early babies need more intensive support. Modern newborn care, steroids, and delivering at a hospital with a NICU all improve the odds.

Will it happen again?

A prior preterm birth is the strongest risk factor for another, with a recurrence of roughly 30%. Vaginal progesterone and, in some cases, a cervical stitch lower that risk, so share your history early in your next pregnancy.

Is there anything I can do to prevent it?

For most people, general steps help: early prenatal care, treating infections, not smoking, spacing pregnancies. If you are higher risk, progesterone, cervical-length monitoring, and cerclage are specific tools your provider can offer.

Medically Reviewed · Updated

Reviewed by Dr. Grace Lin, MD, FACOG · OB-GYN

Obstetrician-gynecologist focused on reproductive and sexual health for women: pregnancy, BV, yeast, trichomoniasis and HPV/cervical screening. Our editorial guidelines →

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