Preterm Labor Guide: Symptoms, Causes, Diagnosis, and Treatment
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: September 2026
TL;DR: Preterm labor is regular contractions that begin opening the cervix between 20 and 37 weeks of pregnancy — before the baby is considered full term. Warning signs include regular belly tightening, low backache, pelvic pressure, cramps, spotting, and leaking fluid. Call your healthcare professional right away if any of these appear. While no treatment stops labor for good, corticosteroids, magnesium sulfate, tocolytics, cerclage, and progesterone can protect the baby and buy time.
Quick Answer
Preterm labor means regular contractions that open the cervix between weeks 20 and 37.
Seven key warning signs deserve an immediate call: regular tightening, backache, pelvic pressure, cramps, spotting, fluid leakage, and changes in vaginal discharge.
Risk factors include a prior preterm birth, multiple pregnancy, short time between pregnancies, and certain infections — but many cases have no clear cause.
Treatment cannot reliably stop labor, but it can protect the baby's lungs and brain and delay delivery long enough for corticosteroids to work.
What is preterm labor, exactly?
Preterm labor happens when the body starts the process of labor — regular contractions that cause the cervix to soften, thin, and open — too early, between 20 and 37 weeks of pregnancy. A full-term pregnancy lasts about 40 weeks, so a baby born after preterm labor may face health problems linked to being born too early.
Not all contractions before 37 weeks mean preterm labor. Many pregnant people feel occasional, irregular tightening called Braxton Hicks contractions, which do not open the cervix. Preterm labor is diagnosed when contractions are regular and are actually changing the cervix.
What are the signs and symptoms of preterm labor?
Signs and symptoms of preterm labor include regular or frequent contractions that cause the belly to tighten like a fist, a dull, low backache, a sense of pressure in the pelvis or lower belly, mild belly cramps, vaginal spotting or light bleeding, a gush or trickle of fluid from the vagina after the membrane around the baby breaks or tears, and a change in the type of vaginal discharge — watery, mucus-like, or bloody.
Braxton Hicks or preterm labor?
If you are not sure whether what you are feeling is true labor, try changing positions, walking, or resting. If the contractions stop, they were likely Braxton Hicks contractions. If they continue, get stronger, or become regular, call your healthcare professional.
When should you call?
Call your healthcare professional right away if you notice any of these warning signs, even if you are unsure. It is always better to be checked and reassured than to wait.
What causes preterm labor, and who is at higher risk?
In many cases, the cause of preterm labor is not clear. Still, certain factors are linked with a higher risk.
Risk factor category | Examples |
Pregnancy history | A previous preterm birth, being pregnant with twins, triplets, or other multiples, a short time between pregnancies (less than 6 months since the last delivery) |
Uterus and cervix conditions | A short cervix, certain uterine or cervical abnormalities, some past uterine surgeries |
Infections and health conditions | Certain infections, especially of the amniotic fluid and lower genital tract, and chronic conditions such as diabetes and high blood pressure |
Why is preterm labor a concern?
Babies born preterm can face a higher risk of health problems, including breathing difficulties, feeding problems, and developmental delays, since organs like the lungs and brain are still maturing. The earlier in pregnancy labor happens, the greater the potential risk, which is why treatment focuses on delaying delivery when possible and protecting the baby when it is not.
How is preterm labor diagnosed?
Test | What it checks |
Pelvic exam | Whether the cervix has started to soften, thin, or open |
Ultrasound | Cervical length, and the baby's position, size, and growth |
Fetal monitoring | Frequency and strength of contractions and the baby's heart rate |
Lab tests | Signs of infection or other factors linked with preterm labor |
How is preterm labor treated?
Treatment divides into two stages: measures taken while you are at risk, and medicines given once labor appears to be underway.
Before labor: cerclage and progesterone
If you are at risk of preterm labor, your healthcare team may suggest ways to keep labor from starting too soon.
During a procedure called cervical cerclage, the cervix is stitched closed with strong sutures. It may be used for people who are less than 24 weeks pregnant, have a history of early premature birth, and have a cervix that is opening or a cervical length less than 25 millimeters — called a short cervix. The sutures are most often removed after 36 weeks, or earlier if needed.
For a short cervix diagnosed before 24 weeks of pregnancy, vaginal progesterone might lower the risk of preterm birth.
Once you are in labor: protecting the baby
No medicines or surgeries can stop labor, except briefly. Instead, treatments focus on giving the baby time and protection.
Medicine | What it does |
Corticosteroids | Lowers the baby's risk of lung problems, bleeding in the brain, severe infection (sepsis), and even death; offered if you are under 37 weeks and at higher risk of delivering in the next 1 to 7 days |
Magnesium sulfate | Offered if you are at high risk of delivering between weeks 24 and 32; some research shows it may lower the risk of cerebral palsy for babies born before 32 weeks |
Tocolytics | Slow contractions for a while and can delay preterm labor for 48 hours — buying time for corticosteroids to work, or time to reach a hospital equipped for premature babies; they do not treat the cause, do not improve baby outcomes, and are not given with preeclampsia (pregnancy-induced high blood pressure) |
If you are at risk of preterm labor and not in a hospital, you might need to see your healthcare team weekly or more often so they can watch for symptoms.
What does not help
Bed rest to manage preterm labor has not been shown to lower the risk of preterm birth. It can lead to blood clots, emotional distress, and muscle weakness.
Can preterm labor be prevented?
You might not be able to prevent preterm labor. But you can do things to support a healthy, full-term pregnancy.
Get regular prenatal care. Prenatal visits allow your healthcare professional to watch your health and your baby's health. If you have a history of preterm labor or have symptoms, you might need to be seen more often. Eat well, since healthy pregnancy outcomes are often linked with healthy eating.
Do not use unhealthy substances. If you smoke, quit — ask your healthcare professional about ways to help. Do not use illegal drugs either.
Think about pregnancy spacing. Some research suggests a link between premature birth and pregnancies that start six months or less after the last delivery. Talk with your healthcare team about pregnancy spacing and birth control.
Manage ongoing health conditions. Chronic conditions such as diabetes, high blood pressure, and obesity may raise the risk. Work with your healthcare team to control them.
If you have a history of preterm labor or premature birth, you are at risk in later pregnancies. Work with your healthcare team to manage risk factors and respond to early symptoms.
How should you prepare for your appointment?
If you have symptoms of preterm labor, contact your healthcare professional right away. You might need medical care right away.
Before the appointment, ask what you need to do while you wait — you may get in to see your team immediately, or you may be asked to limit your activity until then. Ask a loved one or friend to join you, since a support person can help you remember everything you are told. Write down your questions beforehand.
Basic questions to ask include whether you are in labor, whether anything can keep you from delivering early, whether treatments could help the baby, which symptoms mean calling versus going to the hospital, and what the risks would be if your baby is born now.
Your team will likely ask when your symptoms started, how many contractions you are having per hour, whether your vaginal discharge or bleeding has changed, whether you have been around someone infectious or have a fever, whether you have had other pregnancies, miscarriages, or cervical or uterine surgeries not in your record, whether you smoke, and how long it would take you to reach the hospital in an emergency.
Conclusion
Preterm labor is regular contractions that open the cervix between weeks 20 and 37 of pregnancy — sometimes with no identifiable cause and no known risk factors. The seven warning signs, from regular belly tightening to leaking fluid, all deserve an immediate call rather than a wait-and-see approach, and a false alarm is a small price for peace of mind.
While no treatment can stop labor permanently, modern care has real tools: cerclage and progesterone before labor starts, and corticosteroids, magnesium sulfate, and tocolytics once it does — each aimed at protecting the baby and buying precious time.
Frequently Asked Questions
What exactly counts as preterm labor?
Preterm labor is regular contractions that cause the cervix to open after week 20 and before week 37 of pregnancy. Contractions alone do not count — the cervix must be responding by softening, thinning, and opening.
What are the warning signs I should act on?
Regular or frequent belly tightening, dull low backache, pressure in the pelvis or lower belly, mild belly cramps, vaginal spotting or light bleeding, a gush or trickle of fluid, and watery, bloody, or mucus vaginal fluid. Any of these deserves an immediate call to your healthcare professional.
Why did this happen to me with no risk factors?
The cause of preterm labor often isn't clear. Risk factors raise the chance, but preterm labor can happen in a healthy pregnancy with no known risk factors at all.
Is it really preterm labor or just Braxton Hicks?
Braxton Hicks contractions are common and do not mean the cervix is opening. Try walking, resting, or changing positions — if the contractions stop, they were likely Braxton Hicks. If they keep going, call your healthcare professional.
Can doctors stop preterm labor?
No medicine or surgery can stop labor except briefly. Tocolytics can delay it by about 48 hours, which gives corticosteroid treatment time to work or time to reach a hospital equipped for premature babies.
What treatments protect the baby?
Corticosteroids lower the risk of lung problems, brain bleeding, severe infection, and death if delivery is likely within 1 to 7 days. Magnesium sulfate may lower cerebral palsy risk for babies born before 32 weeks.
What is a cervical cerclage, and who gets one?
Cervical cerclage stitches the cervix closed with strong sutures. It may be used before 24 weeks for someone with a history of early premature birth whose cervix is opening or is shorter than 25 millimeters. Sutures are usually removed after 36 weeks.
Does bed rest help?
No. Bed rest has not been shown to lower the risk of preterm birth and can cause blood clots, emotional distress, and muscle weakness.
References
Health information, not medical advice. This article is for general education and is not a substitute for professional diagnosis or treatment. Always consult a qualified healthcare provider about your own health, and seek emergency care for urgent symptoms.
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