Preventing preterm labor starts with understanding your personal risk factors and working with your provider to address the ones you can control. There’s no single intervention that eliminates the risk entirely, but a combination of lifestyle adjustments, proper screening, and targeted medical treatments can meaningfully lower your chances of delivering before 37 weeks.
Know Your Risk Factors
The single strongest predictor of preterm labor is having experienced it before. If you’ve had a previous preterm delivery, your risk in a subsequent pregnancy is significantly higher, and your prenatal care will likely look different as a result.
Beyond history, a wide range of conditions increase risk. Some are related to the uterus and cervix directly: a short cervix (one that begins thinning and opening in the second trimester rather than the third), placenta previa (where the placenta covers the cervical opening), and risk of uterine rupture from a prior cesarean or fibroid removal. Others are systemic health issues, including high blood pressure, diabetes or gestational diabetes, blood clotting disorders, and being significantly underweight or having obesity before pregnancy. Infections also play a role, particularly urinary tract infections, bacterial vaginosis, trichomoniasis, and other sexually transmitted infections. Pregnancies conceived through IVF carry higher risk as well.
One factor many people overlook is the spacing between pregnancies. Conceiving less than six months after giving birth is a recognized risk factor. Research supported by the NIH suggests the optimal interval between delivery and the next conception is 12 to 24 months, with 18 months carrying the lowest risk. If you’re planning a subsequent pregnancy, that window matters.
Reduce Physical Strain and Stress
Physically demanding work during pregnancy has a measurable connection to preterm birth. Prolonged standing, defined as more than four hours per day, is associated with roughly a 22% increase in preterm birth risk based on a pooled analysis of 12 studies. The mechanism is straightforward: heavy lifting and long hours on your feet trigger the release of stress hormones that raise blood pressure, reduce blood flow to the placenta, and can stimulate uterine contractions.
This doesn’t mean you need to be on bed rest (which, notably, has not been shown to prevent preterm birth in most cases). It means paying attention to the physical demands of your daily routine. If your job involves standing for long stretches, heavy lifting, or physically exhausting shifts, talk to your provider about modifications. Many employers are required to offer reasonable accommodations during pregnancy. Regular moderate exercise, like walking or swimming, remains safe and beneficial for most pregnancies. The concern is with sustained, high-intensity physical strain.
Get Screened for Cervical Changes
If you’ve had a previous spontaneous preterm birth, current guidelines from the American College of Obstetricians and Gynecologists recommend serial cervical length measurements using transvaginal ultrasound. These scans track whether your cervix is shortening earlier than it should. A cervix that shortens prematurely is one of the most actionable findings in preterm prevention because it opens the door to specific interventions.
For pregnancies without a history of preterm birth, routine cervical length screening is less standardized, but many providers will check cervical length during the mid-pregnancy anatomy scan around 18 to 22 weeks. If your cervix measures short, your provider can discuss next steps even if this is your first pregnancy.
Cervical Cerclage for a Weakened Cervix
A cervical cerclage is a stitch placed around the cervix to hold it closed during pregnancy. It’s typically offered to people with cervical insufficiency, a condition where the cervix opens too early without contractions, often leading to second-trimester loss. This can result from previous cervical surgeries (such as a LEEP procedure), structural differences in the uterus, or a history of second-trimester miscarriages linked to cervical weakness.
The procedure is successful in about 90% of cases, according to Cleveland Clinic data. It’s usually placed between 12 and 14 weeks of pregnancy and removed around 36 to 37 weeks. If you’ve lost a pregnancy in the second trimester or have known cervical damage, this is one of the most effective preventive tools available.
What Progesterone Can and Cannot Do
Progesterone supplementation has been one of the most studied interventions for preterm birth prevention, and the picture has become more nuanced in recent years. Updated guidance from ACOG clarifies that progesterone is not a blanket preventive measure.
Here’s where things stand: vaginal progesterone may be considered for people who have both a history of preterm birth and a shortened cervix detected on ultrasound. In that specific combination, it can be part of a prevention plan. However, progesterone has not been proven effective for preventing recurrent preterm birth when the cervix is normal length. A meta-analysis found no reduction in recurrent preterm birth from vaginal progesterone in the absence of cervical shortening. Injectable progesterone (17-OHPC), which was once widely used, is no longer recommended for primary prevention of preterm birth in people with a prior preterm delivery.
The key takeaway is that progesterone decisions depend on your cervical length measurements and your pregnancy history together. It’s not something to take “just in case,” and your provider should be tailoring the approach based on your ultrasound findings.
Treat Infections Early
Certain infections during pregnancy are directly linked to preterm labor. Bacterial vaginosis, a common vaginal infection, roughly doubles the odds of preterm delivery when present, even without symptoms. Urinary tract infections, trichomoniasis, and other sexually transmitted infections also increase risk.
The relationship between treating these infections and preventing preterm birth is complicated. For bacterial vaginosis specifically, treating it in people who already have symptoms is standard care. But screening and treating asymptomatic bacterial vaginosis in average-risk pregnancies has not been shown to reduce preterm delivery rates. For people at higher risk (those with a prior preterm birth), some studies have found that treating bacterial vaginosis with oral antibiotics led to significant reductions in preterm delivery, though the evidence is still not considered definitive. The US Preventive Services Task Force currently notes that even in high-risk groups, it remains unclear whether screening for and treating asymptomatic bacterial vaginosis prevents preterm birth.
What you can do: report any unusual discharge, odor, or urinary symptoms to your provider promptly rather than waiting for your next scheduled visit. Symptomatic infections should always be treated during pregnancy.
Testing for Preterm Labor Risk
If you’re experiencing symptoms that could indicate early labor, your provider may use a fetal fibronectin test. This swab test detects a protein that acts like a biological glue between the amniotic sac and the uterine lining. When it shows up in vaginal secretions between 22 and 34 weeks, it can signal that the body is preparing for delivery.
The test is far more useful for ruling out imminent preterm birth than for confirming it. A negative result has a predictive value of about 97%, meaning if the test is negative, there’s a very high likelihood you won’t deliver within the next two weeks. A positive result is much less definitive, with a positive predictive value around 32%. In practical terms, a negative fetal fibronectin test can spare you unnecessary hospitalization and interventions, while a positive result prompts closer monitoring rather than a definitive diagnosis.
Recognize the Warning Signs
Preterm labor doesn’t always announce itself with obvious pain. The signs can be subtle: regular or frequent tightening of the uterus (often painless), a constant low backache, pelvic pressure or a feeling that the baby is pushing down, mild abdominal cramps with or without diarrhea, a change in vaginal discharge (especially watery fluid or discharge tinged with blood), and light vaginal spotting or bleeding.
The challenge is that some of these overlap with normal pregnancy discomfort. The distinguishing feature is pattern and persistence. Occasional tightening is common, but if you notice contractions coming at regular intervals, or if any of these symptoms don’t resolve with rest and hydration, contact your provider immediately. Early intervention during preterm labor, including medications to temporarily stop contractions and steroids to accelerate fetal lung development, can make a significant difference in outcomes if delivery can’t be delayed long enough to reach full term.