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What are preterm labor and preterm birth?
If you start having regular contractions that cause your cervix to begin to open before you reach 37 weeks of pregnancy, 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.
Going into preterm labor does not mean you'll have a premature baby. About half of the women who experience preterm labor eventually deliver at 37 weeks or later.
How often does preterm birth happen?
About 12 percent of babies in the United States are born prematurely, which is about one-third higher than the rate in the early 1980s. More women are using fertility treatments, which makes them more likely to have twins or higher order multiples, who tend to arrive early. Also, more women are delaying pregnancy, and the chance of conceiving multiples goes up as you get older.
About a quarter of preterm births are planned for medical reasons. If you or your baby has a complication and is not doing well, your medical team might decide to induce labor early or perform a cesarean 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.)
The rest are known as spontaneous preterm births. 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).
What are the symptoms of preterm labor?
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
- Abdominal pain, menstrual-like cramping, or six or more contractions in one hour (even if they don't hurt)
- More pressure in the pelvic area (a feeling that your baby is pushing down)
- 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. To catch any potential problems early on, it's a good idea to familiarize yourself with symptoms you should never ignore during pregnancy.
What could happen if my baby is premature?
Many technological advances have been made to help treat preterm infants, and many preterm babies go on to lead healthy lives. Still, the closer a baby is born to term, the better the outlook.
Preterm birth can cause serious health problems or even be fatal for a baby, particularly if it happens very early. In general, the more mature a baby is at birth, the better his chances of surviving and being healthy.
Some preterm babies may have problems breathing. Prematurity also puts a baby at a greater risk for brain hemorrhage. The nervous system, gastrointestinal tract, and other organs may be affected too. Preterm babies are more prone to infection and jaundice and may have difficulty feeding as well as trouble maintaining their body temperature.
Survivors sometimes suffer long-term health consequences, including chronic lung disease, vision and hearing impairment, cerebral palsy, and developmental problems.
Most premature babies are born between 34 and 37 weeks. If these "late preterm infants" have no other health problems, they generally do significantly better than those born earlier, though they still face a higher risk of problems than babies who are born later in pregnancy.
What causes spontaneous preterm birth?
Although the cause is often unknown, a variety of factors may play a role in preterm birth:
Infection -- Certain genital tract infections are associated with preterm delivery. 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.
You may have been checked for chlamydia and gonorrhea at your first prenatal visit. If you'd tested positive for either of these sexually transmitted infections, you and your partner should have been treated immediately, checked again after treatment, and told to use condoms for the rest of the pregnancy.
If you've had a previous preterm birth, you may also have been screened for bacterial vaginosis (BV). Although some studies show that treating bacterial vaginosis (BV) in the second and third trimester reduces the risk of preterm labor in women with a history of preterm birth, other research has found that it makes no difference. So experts don't agree on whether it's worthwhile to test pregnant women who don't have symptoms. (If you have symptoms of bacterial vaginosis, you'll be tested and treated with antibiotics, if needed.)
You probably won't be tested for trichomoniasis unless you have bothersome symptoms.
Certain non-uterine infections, such as a kidney infection, pneumonia, and appendicitis, also raise your risk of preterm birth.
You're also at more risk if you have a type of urinary tract infection known as asymptomatic bacteriuria, a condition in which you have bacteria in your urinary tract but have no symptoms. (This is one reason that all pregnant women should have their urine tested for bacteria.)
- Having a problem with the placenta, such as placenta previa, placenta accreta, or placental abruption
- Having an excessively large uterus, which is often the case when you're pregnant with multiples or have too much amniotic fluid
- Having structural abnormalities of the uterus or cervix. For example, you may have a cervix that's shorter than normal (less than 25 millimeters), that thins out (effaces) or opens (dilates) without contractions. This is known as cervical insufficiency and it may be the result of having had cervical surgery, or it may be something you were born with.
- Having abdominal surgery during pregnancy (to remove your appendix, your gallbladder, or a large or suspicious ovarian cyst, for example)
What are the risk factors for spontaneous preterm birth?
There are a number of risk factors, but keep in mind that more than half of spontaneous preterm births occur in pregnancies in which there's no identifiable risk factor. Although it's impossible to say whether you'll give birth prematurely, it may be more likely if you:
- Previously had a preterm delivery (the earlier in gestation your baby was born and the more spontaneous preterm births you've had, the higher your risk)
- 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
- Are younger than 17 or older than 35
- Are African American
- Were underweight or overweight before you got pregnant or don't gain enough weight during your pregnancy
- Have had vaginal bleeding in the first or second trimester. Vaginal bleeding in more than one trimester means the risk is even higher.
- Had moderate to severe anemia early in your pregnancy
- Smoke, abuse alcohol, or use drugs (especially cocaine) during pregnancy
- Gave birth in the last 18 months (particularly if you became pregnant within six months of giving birth)
- 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 low socioeconomic status
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 an even higher risk, of course, particularly if there's trauma to the abdomen.
There are some studies that suggest women who work the night-shift or have extremely physically demanding jobs may have a higher risk of preterm birth.
Are there tests that can predict my chances of having a preterm delivery?
Two screening tests are available for women who are having symptoms of preterm labor or are otherwise at high risk for it. A negative result is particularly useful because it can put your mind at ease and help you avoid unnecessary interventions and time in the hospital.
The American College of Obstetricians and Gynecologists (ACOG) doesn't recommend using either test routinely for all pregnant women. Studies haven't shown the tests to be useful for women who aren't at high risk and have no symptoms.
These are the two tests:
Measuring the length of your cervix with ultrasound
At your mid-trimester ultrasound (around 20 weeks), your sonographer will look at your cervix and measure its length. A short cervix can be an indicator that you're at higher risk for a preterm delivery.
Your doctor may also order a cervical length measurement if your pregnancy is at high risk for cervical insufficiency because of a history of preterm birth, for example, or if you go to the hospital for symptoms of preterm labor.
If the ultrasound shows that your cervix is short, your provider may recommend that you cut back on physical activity and work, abstain from sex, and stop smoking if you haven't already. Depending on your situation and your baby's gestational age, you could have another ultrasound within the next few weeks.
If you're less than 24 weeks pregnant and your cervix is shortening or dilating but you're not having any contractions, a cerclage may be recommended. For this procedure, a band of strong thread is stitched around your cervix to help hold it closed. Your doctor may suggest a cerclage if you've had a history of possible cervical insufficiency or if you've had a preterm birth before 34 weeks. The cerclage may be placed before there's cervical change or if shortening is noted.
Alternately, depending on your specific case, vaginal progesterone may be offered, as it can reduce the risk of preterm delivery in women with a short cervix.
Fetal fibronectin screening
This test is usually reserved for women who are having contractions or other symptoms of preterm labor. Fetal fibronectin (fFN) is a protein produced by the fetal membranes. If more than a small amount turns up in a sample of your cervical and vaginal secretions between 24 and 34 weeks, you're considered to be at higher risk for preterm delivery.
A positive fFN result might prompt your provider to give you drugs to hold off labor as well as corticosteroids to help your baby's lungs mature more quickly.
However, the test is actually more accurate at telling you when you won't deliver than when you will. If you have a negative fFN result, it's highly unlikely that you'll deliver in the next two weeks. A negative result can put your mind at ease and help you avoid hospitalization or other unnecessary treatment.
What else can I do if I'm at high risk?
- Take care of yourself. If you eat well, get plenty of rest, start your prenatal care early, see your provider regularly, stop unhealthy habits (such as smoking), get to a healthy weight (and gain the right amount of weight during pregnancy), and manage your stress level, you're already doing a lot to ensure a healthy, full-term pregnancy. Depending on your situation, your doctor may recommend that you see a high-risk specialist (a perinatologist) for your care.
Talk with your doctor about medication. If you've previously had preterm premature rupture of the membranes (PPROM) or spontaneous preterm labor resulting in a preterm birth before 37 weeks and are currently carrying only one baby, talk to your provider about treatment with a progesterone compound called Makena (17 alpha hydroxyprogesterone caproate, or 17P for short).
Studies have shown that weekly injections of this hormone, starting at 16 to 20 weeks and continuing through 36 weeks, significantly reduce the risk of a repeat preterm delivery for women in this situation. (In some cases, the medication is started later than 20 weeks.) It doesn't appear to offer any benefit to women carrying more than one baby or with no previous history of preterm labor.
- Pay attention. As your pregnancy progresses, take time to tune into the changes that are happening in your body. 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.
- Learn the signs of preterm labor, and let your provider know right away if you notice any. The most important development in the management of preterm labor in the past 50 years has been the use of corticosteroids to speed up the development of a baby's lungs before birth. The earlier you realize you're in preterm labor, the more likely it is that your baby will be able to benefit from this treatment.
- Avoid bedrest. Some providers will suggest bedrest, though multiple large research studies have shown there's no evidence that it helps prevent preterm birth and in some instances may be detrimental.
What will happen if I start having preterm labor?
If you have signs of preterm labor or think you're leaking amniotic fluid, call your healthcare provider, who will probably have you go to the hospital for further assessment. You'll be monitored for contractions as your baby's heart rate is monitored, and you'll be examined to see whether your membranes have ruptured. Your urine will be checked for signs of infection, and cervical and vaginal cultures may be taken as well. You may also be given a fetal fibronectin test.
If your water hasn't broken, your provider will do a vaginal exam to assess the state of your cervix. An abdominal ultrasound will often be done as well, to check the amount of amniotic fluid present and confirm the baby's growth, gestational age, and position. Finally, some providers will do a vaginal ultrasound to double-check the length of your cervix and look for signs of effacement.
If all the tests are negative, your membranes haven't ruptured, your cervix hasn't dilated after a few hours of monitoring, your contractions have subsided, and you and your baby appear healthy, you'll most likely be sent home. For about 3 in 10 women, preterm labor stops on its own.
Although each provider may manage the situation a little differently, there are some general guidelines for handling preterm labor.
If you're less than 34 weeks (but 24 weeks or more) pregnant and found to be in preterm labor, your membranes are intact, your baby's heart rate is reassuring, and you have no signs of a uterine infection or other problems (such as severe preeclampsia or signs of a placental abruption), your practitioner will probably attempt to delay your delivery. One way she can do this is by giving you special drugs called tocolytics. Tocolytics can delay delivery for up to 48 hours (though they don't always work and are not routinely used).
During that time, if your doctor thinks you're at risk of delivering within 7 days, your baby can be given corticosteroids (drugs that cross the placenta) to help his lungs and other organs develop faster. This will boost his chance of survival and minimizes some of the risks associated with an early birth. Corticosteroids are most likely to help your baby when given between 24 and 34 weeks of pregnancy, but they're also given between 23 and 24 weeks.
If you're less than 32 weeks pregnant and in preterm labor, and your provider thinks you're at risk of delivering in the next 24 hours, you may also be given magnesium sulfate to reduce the risk of cerebral palsy in your baby. (Cerebral palsy, a nervous system disorder, is associated with early preterm birth.)
You'll also get IV antibiotics to prevent group B streptococcal infection(GBS) in your baby. (This is done just in case a culture shows you're a carrier, as it takes 48 hours to get results.)
To take advantage of technological advances in preterm care, a preterm infant is best cared for at a hospital with a neonatal intensive care unit (NICU). If you're in a small community hospital where specialized neonatal care is not available for a preterm infant, you'll be transferred to a larger institution at this point, if possible. (Hospitals generally have limits for gestational how premature a baby they're able to care for.)
You and your baby will be monitored throughout labor if it does continue.
If you haven't reached 24 weeks, neither antibiotics for GBS prevention nor corticosteroids are recommended. Your medical team will counsel you about your baby's prognosis, and you can opt to wait or be induced.
What if my water breaks but I'm not having contractions?
If your water breaks before 34 weeks but you're not having contractions, your medical team may decide to induce labor or may opt to wait, hoping to buy the baby more time to mature. It depends on how far along you are and whether there's any sign of infection or other reason that your baby would be better off being delivered. In any case, unless you've had a recent negative GBS test, you'll be given antibiotics to protect against group B strep.
If you're at 34 weeks or more, and your water had broken, you may be induced or delivered by cesarean section.
On the other hand, if you're less than 34 weeks pregnant, ACOG recommends waiting to deliver unless there's a clear reason to do otherwise.
The purpose of waiting is to try to give your baby more time to mature. The downside is a higher risk of infection. But at early gestational ages, the benefits of waiting usually outweigh the risks of an immediate induction or c-section.
While waiting, you'll receive antibiotics for seven days, to lower the risk of infections and help prolong your pregnancy. You'll also receive a course of corticosteroids to help hasten your baby's lung development.
You and your baby will be monitored carefully during this time. Of course, if you develop symptoms of an infection or there are other signs that your baby is not thriving, you'll be induced or delivered by c-section.
Video: Preemies in the NICU
Premature babies may need to stay in the NICU until their medical problems resolve, they can feed well without issues, and they've grown big enough. See what happens in the neonatal intensive care unit and how the littlest babies are treated.
Read about parenting in the NICU and watch a video about how parents can help their baby in the NICU.