For more information about preterm birth, including the categories of prematurity and the health problems that preemies may face, check out our blog “What is Considered Preterm Birth?”.
How is Preterm Labor Risk Assessed?
Although the causes of spontaneous preterm birth are not fully understood, there are several known risk factors for preterm birth. These include both medical risk factors and lifestyle risk factors.
Medical Risk Factors for Preterm Birth
- Prior miscarriage or preterm birth
- Pregnancy with multiples (twins, triplets, or others)
- Family history of preterm birth (sister, mother, or grandmother)
- Maternal age (17 or younger, 35 or older)
- Problems with the uterus, placenta, or cervix
- Pregnant through in vitro fertilization (IVF)
- Maternal weight (underweight or overweight before pregnancy)
Lifestyle Risk Factors for Preterm Birth
- High stress levels
- Substance use
These preterm birth risk factors are just some of the concerns that doctors consider when determining possible birth outcomes for each mom. While these pregnancy outcomes are important to understand and address as needed, up to half of women who deliver their babies early have no known risk factors for preterm birth.
There are three main methods for screening pregnant moms to assess their risk of preterm birth. These include standard intervention methods and a newer approach.
History of Preterm Birth
An important part of your first prenatal health visit is your patient history. Women who have a history of a previous preterm birth are considered to be at higher risk of delivering early again. In clinical studies, there is clear evidence that the history of a previous premature birth has been able to identify 11% of spontaneous preterm births. Thus, patient history is an important preterm birth prevention strategy.
Cervical Length Screening
Ultrasounds are an important part of routine prenatal testing. Among other measurements, an ultrasound measures the length of the cervix. When the cervix is shorter than average, this can indicate a higher risk of preterm birth. Scientists have found that cervical length screening can detect a further 6% of pregnancies that deliver prematurely.
PreTRM Test for Risk Management
With only 17% of preterm births detectable through standard intervention methods, there has been a great need for a test to measure the risk of preterm birth in women without clear risk factors to help predict outcomes.
Through focused research, scientists found that measuring key proteins in the blood of pregnant women can identify 88% of preterm births in women without known risk factors for preterm birth.
Based on the principles of proteomics—which studies groups of proteins—Sera scientists developed PreTRM, a test that is now available to most pregnant women. It is a simple blood test given during weeks 18 through 20 of pregnancy. With the PreTRM report, moms and doctors can work together to adjust pregnancy care plans to prevent spontaneous preterm birth.
For more about the PreTRM Test, check out PreTRM FAQs for Parents.
How is Preterm Labor Diagnosed?
For most women, it can be difficult to know when preterm labor has started. When it is caught early, there are interventions that can help improve a baby’s chances for a healthy and safe start in life. There are several ways doctors can diagnose early labor and improve women’s chances for a healthy delivery.
Signs and Symptoms of Early Labor
Not every labor begins with a well-defined rush of “water breaking.” It’s important to know that there are other signs and symptoms that may indicate that labor has begun. If you experience any of these symptoms—or other unusual changes—call your doctor right away.
- Contractions every 12 minutes or more often. These feel like your belly is getting tight or bunched up. While it’s normal to have practice contractions during pregnancy, you should see your doctor if you have more than five contractions in an hour.
- Change in vaginal discharge. If your vagina leaks blood, watery mucus, or other fluid, it may be a sign of early labor.
- Pelvic pressure. If you feel that your baby is pushing down on your lower belly or vagina, it may signal labor.
- Backache. Back pain with labor can feel different from other pains you may have felt during your pregnancy. Labor backache may feel constant and dull in your low back, or it may come in waves and move toward your front.
- Cramps. Labor cramps may feel like menstrual cramps. They may occur with or without the side effects of diarrhea.
For more information on the signs and symptoms of premature labor, check out this resource for moms.
How Your Doctor Can Diagnose Early Labor
If your healthcare team believes you may be in labor, they will perform several tests to look for changes in your cervix and uterus and to check on the health of your baby and your chance of preterm delivery.
Your doctor will do a pelvic exam to check the firmness of the uterus and to see whether your cervix has begun to thin out and dilate (open). They will also note the position and size of your baby. Your healthcare provider may repeat the pelvic exam a few times over the course of several hours to help estimate your risk of early delivery.
A transvaginal ultrasound helps your doctor measure the thickness and dilation of your cervix. When the cervix becomes shorter and thinner, it may be evidence of early labor. Ultrasound testing also gives your doctor valuable information about the baby’s health and position, and the amount of amniotic fluid available to keep the baby healthy.
If your doctor suspects that you may be going into early labor, they will use a monitor to measure the timing and strength of any contractions. They may also use a fetal heart rate monitor to study what effect, if any, contractions may be having on the baby’s heart rate. For more information on how contractions and fetal heart rate is measured during pregnancy, read our blog about contraction monitoring.
There are several substances doctors look for in the urine and vagina that can show that labor may have begun. Fetal fibronectin is a protein that helps the amniotic sac stay attached to the inside of the uterus. If a swab of the vagina contains fetal fibronectin, it can be a sign that preterm labor has begun. Other tests your doctor may order include urine tests and swabs that measure the presence of certain bacteria.
Common Preterm Birth Prevention Strategies Supported by Clinical Evidence
Surgical Techniques: Cerclage
If your healthcare provider finds that you are at a high risk of going into labor early, they may recommend a surgery called cerclage to prevent preterm birth. Factors that help a doctor decide whether or not to perform cerclage include a history of preterm birth or miscarriage and a short cervix. In cerclage, the doctor closes the cervix with one or more stitches. This helps reduce the odds of preterm birth.
Care Coordination Intervention
In the holistic care coordination approach, the care team works closely with women at high risk for preterm birth. Care coordination has several components:
- More frequent check-ins. The care coordination model involves weekly check-ins to assess risk with a healthcare provider, either on the phone or through an app.
- Extra help with lifestyle changes. With care coordination, women at high risk of preterm birth get extra help with lifestyle changes that can effect birth outcomes —like quitting smoking and improving food choices—that help keep a pregnancy safely on track and improve mom’s health.
- Patient education. Care coordination lets doctors and other healthcare professionals work closely with pregnant moms to help them understand the signs and symptoms of early labor.
- Preterm birth prevention visit. Under the care coordination model, high-risk pregnant women have a prenatal visit with a doctor to focus on preventing preterm birth.
Strategies to Improve the Health of Baby in the Event of Preterm Birth
Even with the best preterm birth intervention strategies, it’s impossible to avoid all preterm labor. There are several medical strategies that can improve the health of the baby in the event of a preterm birth.
While tocolytics can’t prevent preterm labor, they can delay labor for up to 48 hours. If your doctor diagnoses you with early preterm labor and they believe these drugs will be helpful, they will prescribe tocolytic drugs. The main purpose of tocolytic drugs is to give extra time so the health team can give other medicines to help the baby’s lungs mature. Tocolytics can also delay labor long enough to move a mom from a local community hospital to a specialized hospital with the ability to take better care of preemies.
When doctors know that a pregnancy is likely to end early, they may give the mom corticosteroids. These are often given to mothers between 24 and 34 weeks of pregnancy who are at risk of delivering within a week. When a pregnant woman gets steroids, they travel into the baby’s system to mature the lungs quickly. This helps the baby with breathing after birth.
Moms who are less than 32 weeks pregnant and who may deliver within 24 hours often get magnesium sulfate. This drug may reduce the preterm baby’s risk of cerebral palsy and the effects of other motor issues after birth.
For more information on tocolytics, steroids, and magnesium sulfate, check out these valuable resources from the American College of Obstetricians and Gynecologists and the March of Dimes.
Preterm Birth Rates
One in ten babies is born too soon. In the United States, about 10% of babies are born before they reach full term. Preterm birth is the most common medical challenge facing pregnant moms in the U.S. It is more common than other well-known conditions like preeclampsia, Down Syndrome, and cystic fibrosis.
|Preterm Birth||1 in 101|
|Preeclampsia||1 in 302|
|Down Syndrome||1 in 7003|
|Cystic Fibrosis||1 in 3,5004|
Preterm birth affects more than 1 in 10 U.S. pregnancies.
Preterm birth is a factor in more than one-third of newborn deaths. Prematurity causes a range of health and medical issues that mean more hospital time and more doctor visits for women, babies. and their families. For information on the rates of preterm birth and the health effects of prematurity, check out Premature Birth 101 for parents.
What Can Women Do to Prevent Preterm Births?
The most important things pregnant women can do to prevent a preterm birth are to stay healthy and stay informed. Self-care during pregnancy is vital.
Stay Healthy to Prevent Preterm Birth
In order to give your baby the best chance at a full-term, healthy delivery, it’s important to stay healthy during your pregnancy. Follow guidelines from your medical team and look for resources that are backed by science, such as the National Institute of Child Health and Human Development. Some of the most important recommendations on staying healthy during pregnancy include:
- Avoiding smoking, alcohol, and drugs
- Making healthy food choices
- Taking prenatal vitamins your doctor recommends
- Gaining the suggested amount of weight
- Avoiding infections
- Managing daily stress levels and its effects
- Drinking plenty of fluids
- Staying active (unless your doctor advises against it)
- Keeping high blood pressure, diabetes, and other chronic health problems under control
- Going over your list of drugs and vitamins with your doctor to make sure they are all safe to use while you are pregnant
- Taking good care of your teeth and gums
Stay Informed to Prevent Preterm Birth
Learning about your risk of preterm birth and staying informed about changes in your body are important ways to help prevent preterm birth.
Know Your Risk of Preterm Birth
Consider talking to your doctor about taking the PreTRM Test during week 18 through 20 of your pregnancy to understand your individual risk of preterm birth. With information from this test, you and your doctor can create a pregnancy plan that’s just right for your needs. This plan may include more frequent check-ins with your health team, help with lifestyle changes, more education, and a special preterm birth prevention doctor’s visit.
Know the Signs and Symptoms of Preterm Labor
Make sure you understand the signs and symptoms that may show that you are in preterm labor. These include:
- Contractions every 12 minutes or more often
- Change in vaginal discharge
- Pelvic pressure, or a “pushing down” sensation in your lower belly or vagina
If you have any of these symptoms, or other unusual changes in your body, call your doctor right away.
Preterm birth is a leading cause of health problems for newborns. There are several known risk factors for preterm birth, and some interventions that can make a difference in delaying an early delivery and ensuring the best outcomes for the baby. The best preterm birth interventions are to stay healthy and to stay informed. Knowing your individual risk of preterm birth will help you and your doctor develop a tailored pregnancy plan to reduce your risk of early delivery and to give your baby the best start in life.
- Hamilton BE, et al. Births: Provisional data for 2020. Vital Statistics Rapid Release; no 12. Hyattsville, MD: National Center for Health Statistics. May 2021.
- Preventive Services Task Force. Screening for preeclampsia: U.S. Preventive Services Task Force recommendation statement. JAMA. 2017;317(16):1661–67.
- Mai CT, et al. National population‐based estimates for major birth defects, 2010–2014. Birth Defects Research. 2019; 111(18): 1420-1435.
- O’Sullivan BP, et al. Cystic fibrosis. Lancet. 2009;373(9678):1891–1904.
In this article:
- How is Preterm Labor Risk Assessed?
- How is Preterm Labor Diagnosed?
- How Your Doctor Can Diagnose Early Labor
- Common Preterm Birth Prevention Strategies Supported by Clinical Evidence
- Strategies to Improve the Health of Baby in the Event of Preterm Birth
- Preterm Birth Rates
- What Can Women Do to Prevent Preterm Births?
Talk to your doctor today about the PreTRM Test for your individual risk assessment.