Preterm labor can often be slowed or stopped with medical treatment, especially when caught early. The goal is rarely to halt labor permanently but to buy enough time for treatments that dramatically improve the baby’s outcome, sometimes just 48 hours. What happens next depends on how far along you are, how dilated your cervix is, and how quickly you get to the hospital.
Recognizing Preterm Labor
Preterm labor is defined as regular contractions that cause your cervix to open between 20 and 36 weeks of pregnancy. The key signs to watch for are contractions every 10 minutes or more often, a change in vaginal discharge (especially fluid leaking or bleeding), pelvic pressure that feels like the baby is pushing down, and a low, dull backache that doesn’t go away with position changes. Six or more contractions in one hour is not normal at any point before full term.
Not every contraction means labor. Braxton Hicks contractions are irregular, don’t get closer together, and usually stop when you change position or drink water. True preterm labor contractions follow a pattern, grow stronger over time, and continue regardless of what you do. If you’re unsure, time them for an hour. If they’re consistent and don’t fade, call your provider or go to the hospital.
What Happens at the Hospital
When you arrive, the medical team will put you on a fetal monitor to track your baby’s heart rate and measure your contractions. You’ll have a cervical exam to check for dilation and effacement (thinning). In many cases, an ultrasound will measure your cervical length, since a shorter cervix is a stronger predictor that labor is progressing.
One of the most useful tests is the fetal fibronectin (fFN) test, a vaginal swab that checks for a protein associated with the separation of the membranes from the uterine lining. Its greatest value is ruling labor out: a negative result means there’s a 82 to 99% chance you won’t deliver within the next two weeks. That negative result can spare you unnecessary hospitalization and interventions. A positive result is less definitive but tells your team to prepare for the possibility of an early delivery.
You may be observed for at least two hours so the team can assess whether your contractions are truly regular and whether your cervix is changing. If your cervix is already 3 cm or more dilated before 34 weeks, the chance of delivering preterm is high, and treatment shifts toward preparing the baby rather than stopping labor.
Medications That Slow Contractions
Tocolytics are the main class of drugs used to slow or temporarily stop preterm contractions. They don’t prevent preterm birth altogether. Their primary purpose is to delay delivery long enough, usually 48 hours, for other critical treatments to take effect.
The most commonly used tocolytic works by blocking calcium channels in the uterine muscle. Contractions depend on calcium flowing into muscle cells; blocking that flow relaxes the uterus. This medication is given as a pill and is generally well tolerated, though it can cause flushing, headaches, or a temporary drop in blood pressure.
Another option works by stimulating receptors that relax smooth muscle, essentially telling the uterine muscle to stand down. A third type reduces contractions by blocking the production of prostaglandins, hormone-like chemicals that promote uterine activity. This one is typically limited to pregnancies under 32 weeks because of potential effects on the baby’s circulation if used later.
Your care team will choose based on how far along you are, your medical history, and how your body responds. In some cases, combining approaches works better than a single drug alone.
Treatments That Protect the Baby
Even if labor can’t be fully stopped, two treatments given during this window make a major difference in outcomes.
Corticosteroids for Lung Development
A course of corticosteroid injections accelerates the baby’s lung maturity. The benefit peaks between 2 and 7 days after the first dose, which is why buying at least 48 hours with tocolytics matters so much. Only about 20 to 40% of women evaluated for preterm labor actually deliver in that optimal window, but when they do, the effect on the baby’s breathing ability at birth is significant.
Magnesium Sulfate for Brain Protection
For pregnancies under 30 weeks, magnesium sulfate is given intravenously to protect the baby’s developing brain. It reduces the risk of cerebral palsy and other neurological complications. The standard approach is an initial dose given slowly over 20 to 30 minutes, followed by a continuous low dose. If delivery hasn’t happened within 24 hours, the infusion is stopped. This treatment is used regardless of whether you’re carrying one baby or multiples, and regardless of the cause of preterm labor.
Cervical Cerclage for a Weakened Cervix
If preterm labor is caused by cervical insufficiency, where the cervix opens too early without strong contractions, a cerclage (a stitch placed around the cervix to hold it closed) can extend the pregnancy substantially. In one study of women between 24 and 28 weeks with a dilating cervix, emergency cerclage extended pregnancy by a median of 84 days compared to 63 days with bed rest alone. About 85% of women who received the cerclage gained at least 60 additional days of pregnancy.
The procedure significantly reduced rates of delivery before 28, 32, and 34 weeks and lowered the rate of neonatal hospitalization, all without increasing the risk of infection or membrane rupture. It’s not an option for every situation. Active contractions, vaginal bleeding, signs of infection, or fetal complications rule it out. But when the cause is a weak cervix rather than active labor, cerclage is one of the most effective interventions available.
What About Bed Rest and Hydration?
Bed rest and IV fluids are commonly offered during evaluation, but the evidence for them as treatments is thin. A Cochrane review of 228 women with preterm labor and intact membranes found no difference in preterm delivery rates between those given IV hydration and those on bed rest alone. Rates of delivery before 37, 34, and 32 weeks were statistically identical between groups, as were rates of neonatal intensive care admission.
The exception is if you’re actually dehydrated, in which case rehydrating may help. But for women who aren’t dehydrated, IV fluids don’t appear to slow labor. Prolonged bed rest hasn’t been shown to prevent preterm birth either, and it carries its own risks: blood clots, muscle loss, and the psychological toll of extended immobility. Your provider may still recommend reduced activity or a period of observation, but strict bed rest as a treatment for preterm labor lacks strong evidence.
Preventing a Recurrence in Future Pregnancies
If you’ve had a previous preterm birth or have been found to have a short cervix (25 mm or less on ultrasound between 16 and 24 weeks), vaginal progesterone therapy can reduce the risk of it happening again. This treatment is started between 16 and 24 weeks, depending on when the risk factor is identified, and continued up to 34 to 36 weeks.
For singleton pregnancies, the evidence supporting vaginal progesterone is strong. It also applies to twin or higher-order pregnancies when the cervix is short, though the dose is adjusted (400 mg daily for multiples). Reassuringly, progesterone therapy has not been linked to an increase in birth defects or negative effects on the child’s neurological development after birth. If you’ve delivered early before, this is one of the most well-studied preventive options available for your next pregnancy.