ARTICLE: PRETERM LABOR
What is preterm labor and birth?
You're in preterm labor (also known as premature labor) if you start to have regular contractions that efface and dilate your cervix before 37 weeks of pregnancy. And if you deliver your baby before 37 weeks, that's called a preterm birth and your baby is considered premature. About a quarter of all preterm births are intentional, meaning that the medical team decides to induce labor early or perform a cesarean section because of a serious medical condition in the mother, such as severe or worsening preeclampsia, or in the baby, such as the baby having stopped growing. The remainder are known as spontaneous preterm births and are a result of preterm labor, preterm rupture of the bag of waters (amniotic sac), or a condition known as cervical incompetence, in which the cervix dilates prematurely with no contractions.
Slightly more than 10 percent of all babies in the United States are born prematurely. This number has risen over the years, due in part to an increase in the number of women pregnant with multiples (twins or more), who tend to come early. Preterm birth can be risky or even fatal for the baby if the baby is born too early. The more developed a child is at birth, the more likely he is to survive and the less likely he is to have health problems. Premature babies born between 34 and 37 weeks' gestation generally do very well. If you go into preterm labor before 34 weeks, your medical team may be able to delay your labor until the baby's lungs are more developed.
What causes spontaneous preterm birth?
Though the cause is often unknown, a variety of things can play a role in preterm birth:
• Certain genital tract infections (such as chlamydia or bacterial vaginosis) are associated with an increased risk of preterm labor. Substances produced by bacteria can weaken the bag of waters, causing premature rupture of the membranes. Even when the membranes remain intact, bacteria can get into the amniotic fluid or sac and cause preterm labor. You should have been screened for sexually transmitted diseases like chlamydia and gonorrhea before you got pregnant or at your first prenatal visit and would have been treated immediately if diagnosed. Not all practitioners believe it's necessary to screen for other vaginal infections, like bacterial vaginosis (BV), during pregnancy, especially if you have no symptoms (such as vaginal discharge with a fishy smell) and you're not at high risk of preterm labor for other reasons. While BV can be treated with antibiotics, there's currently not enough evidence to suggest that this treatment helps prevent preterm birth.
• An abnormal placenta or serious structural abnormalities of the uterus or cervix can trigger preterm labor. Having an overdistended, or excessively large, uterus (often the case when a woman is pregnant with multiples) can trigger early labor.
• Other conditions that may be related to preterm labor include certain chronic maternal illnesses such as pregestational diabetes, sickle cell anemia, severe asthma, lupus, inflammatory bowel disease, or chronic active hepatitis; non-uterine infections, such as pyelonephritis (kidney infection); abdominal surgery, such as an appendectomy; trauma to the abdomen; and periodontal (gum) disease.
What are the risk factors for spontaneous preterm birth?
While it's impossible to predict your chances of going into preterm labor, the following factors have been associated with a higher risk for it:
• being pregnant with twins or higher number multiples
• having previously had a preterm delivery
• having an 'incompetent cervix' (meaning your cervix dilates without contractions)
• You have a short cervix (shorter than 25 millimeters)
You may also be an increased risk if you:
• are younger than 17 or older than 35 years old
• are African American
• are of short stature or low pre-pregnancy weight
• have had vaginal bleeding in more than one trimester
• smoke, abuse alcohol, or use drugs (especially cocaine) during pregnancy
A few studies have found an association between high levels of stress and preterm birth. Experts have also been studying occupational factors in an effort to see whether extremely physically demanding jobs or long working hours play a role. One study showed that women who had to stand for long periods (more than 40 hours per week) or were subject to extreme occupational fatigue were more likely to have preterm deliveries. Finally, some researchers are studying the possible effect of genetic factors on the incidence of preterm birth because it seems to be more common in some families. They believe that genetics may explain to some degree the different rates seen among various races, even when other risk factors are taken into account.
Are there any tests that can predict my chances of having preterm labor?
The following screening tests are currently available, but the American College of Obstetricians and Gynecologists (ACOG) doesn't recommend screening low risk women who don't have symptoms of preterm labor and experts aren't yet sure what to do with the test results if they are positive. However, negative results can be helpful in that they might help you avoid unnecessary interventions and time in the hospital.
• Measuring the length of your cervix: If your cervix is getting shorter in mid-pregnancy, that means it's beginning to efface and you're at higher risk for preterm delivery. If you're at high risk, your practitioner may use transvaginal ultrasound to measure your cervical length, but unfortunately, there's nothing you can do if it is found to be too short or effacing early.
• Fetal fibronectin screening: Fetal fibronectin (fFN) is a protein produced by the fetal membranes. If it turns up in a sample of your cervical and vaginal secretions, then you've tested positive. The test is generally reserved for high-risk women or women having early contractions to determine if they are really in preterm labor and at risk for delivery. Studies have shown that a positive fFN test done at 24 weeks' gestation or later is associated with a significantly higher risk of preterm birth, but experts aren't sure what to do about this. On the other hand, a woman with a negative fFN test result is highly unlikely to have a preterm delivery within the next two weeks, so a negative result can put your mind at ease and may help your healthcare provider make decision about your need for treatment or hospitalization.
Another technique called home uterine activity monitoring (HUAM) may not be useful in predicting preterm birth either. To use it, you have to wear a sensor around your abdomen that records daily uterine activity. This system is very expensive and experts question whether it has any value at all in decreasing the rate of preterm delivery.
So, is there anything I can do if I'm at high risk?
Up until now, no treatment has been shown to effectively reduce a woman's risk of preterm labor. But in a recent study, researchers found that weekly injections of a form of progesterone starting in the second trimester reduced the incidence of preterm births by a third in women who had previously had premature babies. If you're in a high-risk group, ask your practitioner if this treatment might be right for you.
Other than that, your practitioner may consult with a high-risk specialist or may direct you to a high-risk clinic if one is available in your area. But mostly you'll just want to be aware of the symptoms so you can contact your provider at the first sign of trouble. Some practitioners may suggest bedrest, though there's controversy over whether this will help.
What are the symptoms of preterm labor?
Call your midwife or doctor right away if you're having any of the following in your second or third trimester (before 37 weeks):
• an increase in vaginal discharge, particularly if it's watery, mucus-like, or bloody (even if it's pink or just tinged with blood)
• spotting (small amounts of vaginal bleeding)
• menstrual-like cramping or more than four contractions in one hour
• an increase in pressure in the pelvic area
• low back pain, especially if you didn't previously have back pain
These symptoms can be confusing because some of them, such as pelvic pressure or low back pain, occur during normal pregnancies, too, and early contractions may just be Braxton-Hicks contractions. But it's always better to be safe than sorry, so call your midwife or doctor right away.
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 practitioner, who will likely have you go to the hospital for further assessment. You'll be monitored for contractions (while your baby's heart rate is monitored at the same time) and have a sterile speculum examination done to check for rupture of membranes. You may have cervical and vaginal cultures taken, too. If your bag of waters is intact, your practitioner will do a vaginal exam to assess how much your cervix is dilated and effaced. Often a practitioner will also do an abdominal ultrasound to check the amount of amniotic fluid present and to confirm the baby's growth, gestational age, and position. Finally, some practitioners will do a vaginal ultrasound to double-check the length of your cervix, but this is not always considered necessary.
Although different practitioners may manage the situation a little differently, if you are less than 34 weeks pregnant, your membranes are intact, and your baby's heart rate is reassuring, your practitioner will attempt to delay delivery for a couple of days. You'll be put on an IV and given antibiotics to prevent Group B streptococcal infection in your baby. You'll also receive corticosteroids to speed up the development of your baby's lungs. Then you'll probably be given some type of medication to inhibit contractions. (Some of the more common drugs used for this purpose include ritodrine, terbutaline, and magnesium sulfate.) If you're in a small community hospital where appropriate neonatal care is not available for a preterm infant, you'll be transferred to a larger institution at this point, if possible. You and your baby will be monitored throughout labor if it does continue.
If your membranes are ruptured but you're not having contractions, your medical team may decide to wait for the onset of labor (which could happen within hours or could take up to a week in the hospital), to induce labor, or to inhibit labor. (In any case, you'll probably be given antibiotics to protect against Group B strep.) How to manage preterm rupture of membranes is a controversial area that involves balancing benefits and risks. Waiting to deliver buys the fetus more time to mature but increases the risk of infection. Of course, if there are clear signs of infection or fetal distress, they'll want you to deliver right away, often by cesarean section.
In most cases, if you're in premature labor after 34 weeks, you'll be allowed to go on and deliver your baby. Babies born between 34 and 37 weeks of gestation, though still premature, generally do fine. They may need a short stay in the neonatal nursery and may have a few short-term health issues, but usually have no long-term problems
You're in preterm labor (also known as premature labor) if you start to have regular contractions that efface and dilate your cervix before 37 weeks of pregnancy. And if you deliver your baby before 37 weeks, that's called a preterm birth and your baby is considered premature. About a quarter of all preterm births are intentional, meaning that the medical team decides to induce labor early or perform a cesarean section because of a serious medical condition in the mother, such as severe or worsening preeclampsia, or in the baby, such as the baby having stopped growing. The remainder are known as spontaneous preterm births and are a result of preterm labor, preterm rupture of the bag of waters (amniotic sac), or a condition known as cervical incompetence, in which the cervix dilates prematurely with no contractions.
Slightly more than 10 percent of all babies in the United States are born prematurely. This number has risen over the years, due in part to an increase in the number of women pregnant with multiples (twins or more), who tend to come early. Preterm birth can be risky or even fatal for the baby if the baby is born too early. The more developed a child is at birth, the more likely he is to survive and the less likely he is to have health problems. Premature babies born between 34 and 37 weeks' gestation generally do very well. If you go into preterm labor before 34 weeks, your medical team may be able to delay your labor until the baby's lungs are more developed.
What causes spontaneous preterm birth?
Though the cause is often unknown, a variety of things can play a role in preterm birth:
• Certain genital tract infections (such as chlamydia or bacterial vaginosis) are associated with an increased risk of preterm labor. Substances produced by bacteria can weaken the bag of waters, causing premature rupture of the membranes. Even when the membranes remain intact, bacteria can get into the amniotic fluid or sac and cause preterm labor. You should have been screened for sexually transmitted diseases like chlamydia and gonorrhea before you got pregnant or at your first prenatal visit and would have been treated immediately if diagnosed. Not all practitioners believe it's necessary to screen for other vaginal infections, like bacterial vaginosis (BV), during pregnancy, especially if you have no symptoms (such as vaginal discharge with a fishy smell) and you're not at high risk of preterm labor for other reasons. While BV can be treated with antibiotics, there's currently not enough evidence to suggest that this treatment helps prevent preterm birth.
• An abnormal placenta or serious structural abnormalities of the uterus or cervix can trigger preterm labor. Having an overdistended, or excessively large, uterus (often the case when a woman is pregnant with multiples) can trigger early labor.
• Other conditions that may be related to preterm labor include certain chronic maternal illnesses such as pregestational diabetes, sickle cell anemia, severe asthma, lupus, inflammatory bowel disease, or chronic active hepatitis; non-uterine infections, such as pyelonephritis (kidney infection); abdominal surgery, such as an appendectomy; trauma to the abdomen; and periodontal (gum) disease.
What are the risk factors for spontaneous preterm birth?
While it's impossible to predict your chances of going into preterm labor, the following factors have been associated with a higher risk for it:
• being pregnant with twins or higher number multiples
• having previously had a preterm delivery
• having an 'incompetent cervix' (meaning your cervix dilates without contractions)
• You have a short cervix (shorter than 25 millimeters)
You may also be an increased risk if you:
• are younger than 17 or older than 35 years old
• are African American
• are of short stature or low pre-pregnancy weight
• have had vaginal bleeding in more than one trimester
• smoke, abuse alcohol, or use drugs (especially cocaine) during pregnancy
A few studies have found an association between high levels of stress and preterm birth. Experts have also been studying occupational factors in an effort to see whether extremely physically demanding jobs or long working hours play a role. One study showed that women who had to stand for long periods (more than 40 hours per week) or were subject to extreme occupational fatigue were more likely to have preterm deliveries. Finally, some researchers are studying the possible effect of genetic factors on the incidence of preterm birth because it seems to be more common in some families. They believe that genetics may explain to some degree the different rates seen among various races, even when other risk factors are taken into account.
Are there any tests that can predict my chances of having preterm labor?
The following screening tests are currently available, but the American College of Obstetricians and Gynecologists (ACOG) doesn't recommend screening low risk women who don't have symptoms of preterm labor and experts aren't yet sure what to do with the test results if they are positive. However, negative results can be helpful in that they might help you avoid unnecessary interventions and time in the hospital.
• Measuring the length of your cervix: If your cervix is getting shorter in mid-pregnancy, that means it's beginning to efface and you're at higher risk for preterm delivery. If you're at high risk, your practitioner may use transvaginal ultrasound to measure your cervical length, but unfortunately, there's nothing you can do if it is found to be too short or effacing early.
• Fetal fibronectin screening: Fetal fibronectin (fFN) is a protein produced by the fetal membranes. If it turns up in a sample of your cervical and vaginal secretions, then you've tested positive. The test is generally reserved for high-risk women or women having early contractions to determine if they are really in preterm labor and at risk for delivery. Studies have shown that a positive fFN test done at 24 weeks' gestation or later is associated with a significantly higher risk of preterm birth, but experts aren't sure what to do about this. On the other hand, a woman with a negative fFN test result is highly unlikely to have a preterm delivery within the next two weeks, so a negative result can put your mind at ease and may help your healthcare provider make decision about your need for treatment or hospitalization.
Another technique called home uterine activity monitoring (HUAM) may not be useful in predicting preterm birth either. To use it, you have to wear a sensor around your abdomen that records daily uterine activity. This system is very expensive and experts question whether it has any value at all in decreasing the rate of preterm delivery.
So, is there anything I can do if I'm at high risk?
Up until now, no treatment has been shown to effectively reduce a woman's risk of preterm labor. But in a recent study, researchers found that weekly injections of a form of progesterone starting in the second trimester reduced the incidence of preterm births by a third in women who had previously had premature babies. If you're in a high-risk group, ask your practitioner if this treatment might be right for you.
Other than that, your practitioner may consult with a high-risk specialist or may direct you to a high-risk clinic if one is available in your area. But mostly you'll just want to be aware of the symptoms so you can contact your provider at the first sign of trouble. Some practitioners may suggest bedrest, though there's controversy over whether this will help.
What are the symptoms of preterm labor?
Call your midwife or doctor right away if you're having any of the following in your second or third trimester (before 37 weeks):
• an increase in vaginal discharge, particularly if it's watery, mucus-like, or bloody (even if it's pink or just tinged with blood)
• spotting (small amounts of vaginal bleeding)
• menstrual-like cramping or more than four contractions in one hour
• an increase in pressure in the pelvic area
• low back pain, especially if you didn't previously have back pain
These symptoms can be confusing because some of them, such as pelvic pressure or low back pain, occur during normal pregnancies, too, and early contractions may just be Braxton-Hicks contractions. But it's always better to be safe than sorry, so call your midwife or doctor right away.
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 practitioner, who will likely have you go to the hospital for further assessment. You'll be monitored for contractions (while your baby's heart rate is monitored at the same time) and have a sterile speculum examination done to check for rupture of membranes. You may have cervical and vaginal cultures taken, too. If your bag of waters is intact, your practitioner will do a vaginal exam to assess how much your cervix is dilated and effaced. Often a practitioner will also do an abdominal ultrasound to check the amount of amniotic fluid present and to confirm the baby's growth, gestational age, and position. Finally, some practitioners will do a vaginal ultrasound to double-check the length of your cervix, but this is not always considered necessary.
Although different practitioners may manage the situation a little differently, if you are less than 34 weeks pregnant, your membranes are intact, and your baby's heart rate is reassuring, your practitioner will attempt to delay delivery for a couple of days. You'll be put on an IV and given antibiotics to prevent Group B streptococcal infection in your baby. You'll also receive corticosteroids to speed up the development of your baby's lungs. Then you'll probably be given some type of medication to inhibit contractions. (Some of the more common drugs used for this purpose include ritodrine, terbutaline, and magnesium sulfate.) If you're in a small community hospital where appropriate neonatal care is not available for a preterm infant, you'll be transferred to a larger institution at this point, if possible. You and your baby will be monitored throughout labor if it does continue.
If your membranes are ruptured but you're not having contractions, your medical team may decide to wait for the onset of labor (which could happen within hours or could take up to a week in the hospital), to induce labor, or to inhibit labor. (In any case, you'll probably be given antibiotics to protect against Group B strep.) How to manage preterm rupture of membranes is a controversial area that involves balancing benefits and risks. Waiting to deliver buys the fetus more time to mature but increases the risk of infection. Of course, if there are clear signs of infection or fetal distress, they'll want you to deliver right away, often by cesarean section.
In most cases, if you're in premature labor after 34 weeks, you'll be allowed to go on and deliver your baby. Babies born between 34 and 37 weeks of gestation, though still premature, generally do fine. They may need a short stay in the neonatal nursery and may have a few short-term health issues, but usually have no long-term problems
