Preterm labor

What is preterm labor?

If you start having regular contractions that cause your cervix to begin to open (dilate) after 20 weeks of pregnancy but before you reach 37 weeks, you're in preterm labor. It's also known as premature labor. If you deliver your baby before 37 weeks, it's called a preterm birth and your baby is considered premature.

About 10 percent of babies in the United States are born prematurely. Eighty percent are spontaneous preterm births, which means the labor began on its own. You may end up having a spontaneous preterm birth if you go into labor prematurely, if your water breaks early (known as preterm premature rupture of membranes, or PPROM), or if your cervix opens prematurely with no contractions (known as cervical insufficiency).

The remaining 20 percent of preterm births are planned for medical reasons. If you or your baby has a complication and isn't doing well, your medical team might decide to induce labor early or perform a c-section before 37 weeks. (This might happen if you have a serious medical condition such as severe or worsening preeclampsia, or if your baby has stopped growing, for example.)

But going into preterm labor doesn't mean you'll have a premature baby. Between 30 and 50 percent of women who experience spontaneous preterm labor eventually deliver at 37 weeks or later.

Signs and symptoms of preterm labor

Signs and symptoms of preterm labor are like those of labor at full term. Call your midwife or doctor right away if you're having any of the following symptoms before 37 weeks:

• More vaginal discharge than usual
• A change in the type of discharge – if you're leaking watery fluid or your discharge becomes watery, mucus-like, or bloody (even if it's pink or just tinged with blood)
• Any vaginal bleeding or spotting
• Pelvic or lower abdominal pressure or pain that's new, different, or more intense
• Menstrual-like cramping
• Regular or frequent contractions (even if they don't hurt). Call if you have more than six contractions in one hour that continue even after lying down and hydrating.
• Low back pain, especially if it's dull or rhythmic, or you didn't previously have back pain
• Your water breaks, either in a gush or a trickle

These symptoms can be confusing because some of them, such as pelvic pressure or low back pain, are common during pregnancy, and sporadic early contractions may just be Braxton Hicks contractions. But it's always better to be safe than sorry, so call your healthcare provider right away if you're experiencing anything unusual at any time during your pregnancy.

What causes preterm labor?

Although the cause is often unknown, a variety of factors may play a role in preterm labor:

Infection

Urinary tract infections, sexually transmitted infections (such as chlamydia and gonorrhea), and some vaginal infections (such as trichomoniasis and bacterial vaginosis) may cause preterm labor.

Substances produced by bacteria in the genital tract can weaken the membranes around the amniotic sac and cause it to rupture early. Even when the membranes remain intact, bacteria can cause infection and inflammation in the uterus, which may trigger a chain of events that leads to preterm labor.

It's important to identify and treat any infection as soon as possible. Your provider may have checked (and treated you, if necessary) for STIs at your first prenatal visit. If you've had a previous preterm birth, you may also have been screened for bacterial vaginosis (BV). Because you can have a UTI without symptoms, your urine will be checked for bacteria early in pregnancy.

Certain non-genital infections, such as a kidney infection, pneumonia, appendicitis, gum disease, food poisoning, and COVID-19, also raise your risk of preterm birth.

Placental problems

Having a problem with the placenta, such as placenta previa, placenta accreta, or placental abruption can cause vaginal bleeding and trigger preterm labor.

A large uterus

The stretching of an excessively large uterus – which is sometimes the case when you're pregnant with multiples or have too much amniotic fluid – can lead to uterine contractions and preterm labor.

Risk factors for preterm labor

There are a number of these, but keep in mind that most preterm births happen in women with no risk factors. Although it's impossible to say whether you'll go into labor prematurely, it may be more likely if you:

• Previously had a preterm delivery. This is the strongest risk factor, though most women who have had a preterm birth go on to have a term pregnancy at a later date. A past preterm birth doubles or triples the likelihood of another preterm birth, and the risk is highest if you've had more than one preterm birth.
• Have a family history of preterm birth (such as a mother, grandmother, or sister who had a premature baby)
• Are pregnant with twins or other multiples
• Have a short cervix early in pregnancy
• Have an abnormally shaped uterus
• Have had certain past gynecologic conditions or surgeries
• Have a cervical injury from a past delivery
• Are younger than 17
• Are African American. Black women have double the incidence of preterm labor and birth compared to white women.
• Were underweight or overweight before you got pregnant or don't gain enough weight during your pregnancy
• Have had vaginal bleeding during pregnancy. Vaginal bleeding in more than one trimester means the risk is even higher.
• Smoke, abuse alcohol, or use recreational drugs (especially cocaine) during pregnancy
• Gave birth in the last 18 months
• Have had no prenatal care or got a late start on prenatal care
• Are pregnant with a single baby that's the result of fertility treatments
• Are pregnant with a baby who has certain birth defects, such as spina bifida or heart defects
• Have dietary deficiencies
• Have certain medical conditions, such as connective tissue disorders, diabetes/gestational diabetes, high blood pressure, preeclampsia, intrahepatic cholestasis of pregnancy ( a liver condition that happens during pregnancy) and thrombophilias (conditions that increase your risk of making abnormal blood clots)
• Have excessive amniotic fluid
• Had moderate to severe anemia early in pregnancy
• Work at a physically demanding job that requires you to work long hours or stand for long periods

There also appears to be an association between high levels of stress, especially chronic stress, and preterm birth. The theory is that severe stress can lead to the release of hormones that can trigger uterine contractions and preterm labor.

This may explain why women who are victims of domestic abuse have a higher risk for spontaneous preterm labor. Those who endure physical violence have the greatest risk, particularly if there's trauma to the abdomen.

Preventing preterm labor

You can't control whether you go into labor early, but there are some ways to reduce your risk.

Before pregnancy:

• Wait at least 18 months before getting pregnant after childbirth. The amount of time varies, so talk with your healthcare provider about what's best for you.
• Manage chronic health conditions. Before you become pregnant – and during pregnancy – take care of any conditions you may have, such as high blood pressure or diabetes.
• Start pregnancy at a healthy weight and gain the appropriate amount of weight during pregnancy.
• Take care of your teeth and gums. Get regular dental care and treat cavities and gum disease. Brush and floss regularly.

During pregnancy:

• Get good prenatal care. Schedule your first prenatal appointment as soon as you think you're pregnant. Attend all of your prenatal appointments, even if you feel fine. If you have a high-risk pregnancy, your provider may recommend a maternal-fetal medicine doctor.
• Don't drink alcohol. Drinking during pregnancy is associated with preterm birth. Likewise, don't smoke, and don't abuse drugs.
• Eat a healthy diet. Research suggests that eating a healthy diet during pregnancy – with high intakes of vegetables, fruits, whole grains, low-fat dairy, and lean protein foods – is associated with a lower risk of preterm birth.
• Protect yourself from infections. Wash your hands often, avoid others who may be ill, and get all of your required and suggested vaccinations. Don't eat foods that aren't safe during pregnancy, such as raw or undercooked meat, fish, or eggs. Have only safe sex.
• Take time to tune in to the changes that are happening in your body as your pregnancy progresses. If possible, spend some quiet time each day by yourself so you can focus on your baby's movements and take note of any unusual aches or pressures. To catch any potential problems early on, it's a good idea to familiarize yourself with symptoms you should never ignore during pregnancy.
• Learn the signs of preterm labor, and let your provider know right away if you notice any. The sooner you get treatment, the better for your baby. (See below.)
• Avoid bedrest. There's no evidence that bedrest helps prevent preterm birth, but it can increase the risk of blood clots, bone weakening, and loss of muscle strength.

If you've had preterm labor in the past, your provider may recommend:

• Medication. If you're carrying one baby, your provider may recommend a progesterone supplement. This is usually given as an injection between 16 and 24 weeks of pregnancy and continued until 36 weeks. If you have a short cervix, you may be given progesterone as a daily vaginal supplement, even if you have no history of preterm birth.
• Cerclage. If you have a short cervix, or have had cervical insufficiency before and are pregnant with one baby, your provider may suggest a cerclage – a stitch around the cervix to help keep it closed. This is usually done in the early second trimester.

What to do if you're having premature labor

If you have any of the signs or symptoms of preterm labor listed above (such as vaginal bleeding, water breaking, cramping, or pelvic pressure) contact your doctor or midwife right away.

If you're in preterm labor, you'll be admitted to the hospital and monitored. You may have:

• An ultrasound to help determine the size of your baby and the gestational age (if you haven't had any prior prenatal care).
• A transvaginal ultrasound to check the length of your cervix if you're before 24 weeks.
• A fetal fibronectin test. This is done with a vaginal swab. Fetal fibronectin is a protein that helps the amniotic sac stay connected to the uterus. Just before labor, when the fetal membranes begin to change, fetal fibronectin is released, indicating that there's an increased chance of preterm birth. A negative test means that it's very unlikely you'll give birth in the next week or so. A positive test won't tell you that you're in labor or even that you're about to be in labor, but it can be useful in combination with your ultrasound.

You may also be given medications to help make the outcome safer for your baby:

• Tocolytics can help delay delivery up to 48 hours. These medications don't address the cause of preterm labor, but they can help stop or delay the frequency of contractions. Delaying delivery can allow time for other medications that help your baby to take effect. It can also give you a window to be transferred to a hospital that's better equipped to handle a preterm delivery and care for a preterm baby, if necessary.
• Steroids can help your baby's lungs, brain, and digestive organs develop more quickly. Steroids are best given at least 48 hours but no more than a week before your baby's birth. They're not usually given before 23 weeks, because the fetus is too young to benefit. Talk with the neonatologist and high-risk obstetricians at the hospital for more information.
• Magnesium sulfate can help reduce the risk of cerebral palsy and problems with physical movement.

Read more about how and when steroids are helpful during preterm labor.

What will happen to my baby if I have a preterm birth?

A baby's brain, lungs, liver, and other organs continue to develop in the final weeks of pregnancy, so babies born prematurely haven't had a chance for these organs to fully develop. They may have difficulty breathing, controlling their temperature, and feeding. They may have vision problems, hearing problems, and problems with their intestines and nervous systems. Preemies may also suffer developmental delays.

Babies born before 32 weeks have a higher risk of death. According to the Centers for Disease Control and Prevention, preterm birth and low birth weight account for about 17 percent of infant deaths (before one year of age).

While preterm birth can cause serious health problems or even be fatal for a baby (particularly if it happens very early), many technological advances have been made to help treat preterm infants. Many preterm babies go on to lead healthy lives.

If you have a preterm birth, your baby will have a team of healthcare professionals, including a neonatologist, caring for them. Depending on how early your preemie is born, they may need to stay in the neonatal intensive care unit (NICU) for some time (weeks or months). Traditionally parents are told to expect their baby to be in the NICU until their due date. Some babies are discharged earlier, others later.

In the NICU, your baby will be monitored continuously. They'll be weighed at least once a day. It's a good sign once a preemie starts gaining weight at a steady pace.

Your baby may also have tests to look for any problems they may have as a result of prematurity. These tests include:

• Blood tests for jaundice, low blood sugar, infections, and levels of blood gases (to determine if they need additional oxygen or mechanical ventilation)
• An ultrasound to check for bleeding in the brain
• An echocardiogram to check for heart defects
• A standard hearing test
• Standard state infant screening for diseases like PKU and hypothyroidism
• A retinopathy of prematurity (ROP) examination, to check your baby's eyes
• Urine tests to determine whether your baby's kidneys are functioning properly and whether your baby has an infection
• X-rays to look at your baby's lungs and other organs

Find out the outlook for a premature baby at 28, 31, 33, or 36 weeks.