Preterm Labor FAQsA normal pregnancy lasts 37 to 42 weeks. Preterm labor is defined as labor (contractions with dilation or effacement of the cervix, or both) that occurs before the 37th week of pregnancy. Not all women who experience preterm labor will deliver early. Some women are at a higher risk for preterm labor than others. If you have been diagnosed with a short cervix, or you have a history of preterm labor with a previous pregnancy, you have a greater likelihood of preterm labor with future pregnancies. Sometimes, the reason is unclear. Other circumstances that place a woman at a higher risk include:
- If you are pregnant with more than one baby
- If you are a smoker
- If you have an infection within your uterus
- If you have had surgery on your cervix that required a large part of the cervix to be removed, such as a cone biopsy or conization due to an abnormal Pap smear
- If you have any abnormalities with your uterus
- If you use illicit drugs such as cocaine
- If you have an abnormally large amount of amniotic fluid (Polyhydramnios)
- If your last delivery was less than 12 to 18 months ago
- If you have a severe case of anemia
- If you were at a low weight before pregnancy and did not gain very much weight during the pregnancy
- If you are African-American
- If you are under 18 years of age
- If you have had abdominal surgery during your pregnancy
- If you have been diagnosed with placenta previa1
- If you experience a placental abruption
- If you experience too much physical or emotional stress during your pregnancy, which may cause your body to release the hormone oxytocin that causes contractions
- If you have a shorter than normal cervix
Premature Rupture Of MembranesIn some cases, a woman's membranes (bag of water) break before her pregnancy is considered to be full term (37th week of pregnancy or more). This may happen with or without contractions. If your water breaks between 34 weeks and 36 weeks, 6 days of your pregnancy, it is recommended that no treatment take place to delay the birth of your baby. It is not recommended that you receive corticosteroids because you are in your 34th week of pregnancy or more. If you are under 32 weeks into your pregnancy, you may receive magnesium sulfate to reduce the risk of neurological problems in your baby due to a premature birth. If your culture for Group B Strep has not yet been done, or if the results of the culture are unknown, you should receive an antibiotic to prevent a Group B Strep infection in your baby. If your water breaks and you are between 24 weeks and 33 weeks, 6 days of your pregnancy, it is recommended that you receive a dose of corticosteroids to speed up the development of baby's lungs. You should receive intravenous antibiotics to prevent Group B Strep infection in your baby. If you are not in labor (no contractions or no dilation of your cervix), your physician, or midwife, may choose to treat you with antibiotics to reduce the risk of infection for both you and your baby (Chorioamnionitis), as well as prolong the period of time before you deliver. You should remain in the hospital, where you will be closely monitored for signs of infection and signs of labor. If you show signs of an infection, it is recommended that your baby be delivered.
Symptoms Of Preterm LaborPreterm labor may begin with vague symptoms such as the feeling of pressure in your lower abdomen or pelvis. You may have a dull ache in your lower back. You may experience cramping (similar to cramps during your period), or have vaginal discharge that is mucousy, watery or bloody. You may feel your stomach tightening. If you have more than six contractions in one hour after lying down, contact your physician or midwife right away. If you experience any symptoms of preterm labor, it is important that you contact your physician or midwife immediately. Sometimes, women assume that the cramping, or tightening, they feel are simply Braxton Hicks contractions (false labor contractions). While this is normal during the last weeks of pregnancy, it is important that you do not assume that this is what is causing your symptoms. The only way to tell whether or not you are in labor is to perform a vaginal exam to check to see if your cervix is dilated. When you arrive in labor and delivery, a fetal monitor will be applied that will show any contractions that you are having, as well as monitor your baby's heart rate pattern. A vaginal exam will be performed by a labor and delivery nurse or your physician or midwife, to check to see if your cervix is dilated. Before this exam, you may have a fetal fibronectin test. Fetal fibronectin is a protein that is responsible for holding your baby in the uterus. This protein is normally not detected before the 35th week of pregnancy. This involves a cotton swab being inserted into the vagina. The swab is then placed into a sealed vial and sent to the lab for testing. It is important that the sample be taken before a vaginal exam is performed. If you have had intercourse within the past 24 hours, the test should not be done due to the risk of a false positive result. A negative result is the most reassuring, meaning that the chances of your baby being born in the next seven to 14 days is less than 93 percent.2
Treatment For Preterm LaborThere are very common – and very safe – treatments available for moms who are diagnosed with preterm labor. All medications carry some risks, of course, but your doctor will explain what those risks are, so you can make an informed decision about your health and the health of the baby. The more commonly prescribed methods and medications for treating preterm labor include: Corticosteroids If you are diagnosed with preterm labor between your 24th and 34th week of pregnancy, you should receive a dose of corticosteroids (Betamethasone or Dexamethasone) to help increase the development of your baby's lungs, reducing the severity of respiratory problems after the baby's birth. The medications also reduce the risk of intracranial hemorrhage (bleeding within the brain) in premature babies. According to the American College of Obstetricians and Gynecologists, administering corticosteroids to a woman in preterm labor is the most important action to improve the health, as well as for survival of babies born prematurely.3 If you have not delivered in 24 hours from the first injection, you should receive a second dose of the steroids. Even though your baby will receive some benefit from the first dose, the full benefit of the steroid occurs if delivery occurs after the second dose. Tocolytics If you have not reached the 34th week of pregnancy, you may receive medication to stop or reduce the frequency of your contractions. These medications are called tocolytics. Although they may not be effective in stopping labor, they may slow it down, allowing time for the corticosteroids to work to speed up development of your baby's lungs. They may also allow extra time to transport you to another hospital that is better equipped to care for your baby when he is delivered.2 Tocolytics medications are intended to be used on a short-term basis. It is not recommended that you receive them for an extended period of time. It is recommended that all tocolytics medications be stopped 48 hours after the first dose of a corticosteroids is given. 3 Indomethacin If you are between the 24th and 32nd week of pregnancy, the ACOG recommends that you receive this medication first in an attempt to stop preterm labor. The normal dosage is 50 milligrams orally for the first dose, then 25 milligrams orally every six hours for no longer than 72 hours. If this medication does not stop preterm labor, it is recommended that it be stopped and Nifedipine be given instead (as a second-line drug).3 Terbutaline This may be given by intravenous infusion, or as a subcutaneous injection (under the skin) every 30 minutes. Terbutaline is not recommended to be given as the first medication given to stop contractions. It is considered to be a second-line drug, which means it is given when the first medication did not stop your labor. If you are between the 32nd and 34th week of pregnancy and Nifedipine did not stop your contractions, your physician may stop the Nifedipine and start Terbutaline.3 Nifedipine If you are between the 32nd and 34th week of pregnancy, the American College of Obstetricians and Gynecologists recommend that this medication be given first in an attempt to stop preterm labor. The usual dose is 20 milligrams orally every six hours. Magnesium sulfate Magnesium sulfate is a drug that is commonly given to women in preterm labor to stop or reduce the frequency of uterine contractions, and delay delivery of the baby. It is only given by intravenous infusion on an infusion pump. It works by reducing that amount of calcium in your muscles, making it more difficult for the muscles to contract. Your uterus contains muscle cells. Reducing the amount of calcium that is available to the muscle cells in the uterus makes it more difficult for the uterus to contract. Depending upon how dilated your cervix is, this drug may delay delivery for several days, allowing more time for the corticosteroids to mature your baby's lungs.2 Side effects of magnesium sulfate include flushing of the face, sweating and weakness. Many women relate the side effects of the drug as similar to having the flu. If you are in preterm labor and receive an intravenous infusion of magnesium sulfate, it is extremely important that the physicians and nurses monitor you very closely for signs of magnesium toxicity. Your blood pressure should be monitored very closely when the infusion is started. This is due to the fact that a loading dose is usually given (a certain amount of the drug over a short time). Your reflexes should also be checked according to the hospital's policy for monitoring patients on magnesium sulfate. The staff will pay close attention to your rate of breathing. They will listen to your breath sounds at regular intervals. They will check your reflexes on a regular basis. They will ask you to squeeze their hands. They will also ask you to push down on their hands with your feet. They will also monitor your urine output due to the fact that the drug is removed from your body by your kidneys. If you show signs of magnesium sulfate toxicity, the infusion should be turned off immediately. Your physician should be notified, and you should have blood drawn to check the magnesium level in your bloodstream. If your symptoms of toxicity are severe, you may receive a dose of calcium gluconate, which is the antidote for magnesium sulfate toxicity. You should not receive magnesium sulfate for more than seven days due to the risk of the drug weakening your baby's bones.3 Magnesium sulfate is considered to be neuroprotective to your baby, which means it reduces the risk of a baby developing cerebral palsy due to premature birth. Antibiotics You should also receive an intravenous antibiotic to protect your baby from infection, especially Group B Strep. Group B Strep cultures are usually performed around the 36th week of pregnancy. If you go into labor before that time, it is unknown whether or not the bacteria are present. In cases where antibiotics were not given to a mother who had a positive Group B Strep culture, a culture was not done or the results of the culture are unknown, her baby is at risk for developing a serious infection. Progesterone If you have a history of delivering a premature baby (before 37 weeks), your physician may recommend that you receive progesterone with your next pregnancy. This medication is available by injection, or a vaginal cream, and is usually started between your 16th and 26th week of pregnancy. The medication is stopped when you reach the 36th week of pregnancy.
- DeCherney, A., Nathan, L., Laufer, N., & Roman, A. (2013). CURRENT Diagnosis & Treatment: Obstetrics & Gynecology. New York, NY: McGraw-Hill.
- Simhan, H., & Caritis, S. (2016). Inhibition of acute preterm labor. UpToDate. Retrieved from https://www.uptodate.com/contents/inhibition-of-acute-preterm-labor
- Practice Bulletin No. 159. (2016): Management of preterm labor. The American College of Obstetricians &Gynecologists, 127(1), e29-e38. doi: 10.1097/AOG.0000000000001265