Preterm labor occurs between the 20th and 37th week of pregnancy. This labor includes both uterine contractions and cervical changes.
A full-term pregnancy lasts 38-42 weeks but preterm labor can lead to early delivery. Infants born before 37 weeks are considered premature.
In most cases, the cause is of preterm labor is unknown.
Some preterm labor is associated with preterm premature rupture of membranes (PPROM). PPROM is the rupture of both the amniotic sac and chorion membranes. It generally occurs at least 1 hour before labor begins.
The chance of preterm-labor is greatest in women under the age of 18 years or over 35 years. Other maternal factors that may increase the chance of preterm labor include:
- Low socioeconomic status
- Lack of prenatal care and social support
- Being underweight or obese before becoming pregnant
- Physical, sexual, or emotional abuse
- Severe depression or anxiety
- High blood pressure
- Celiac disease
- Clotting disorders
- Hormonal imbalance
- Certain medications or exposure to diethylstilbestrol (DES)
- Illicit drug use
- Alcohol use
Pregnancy complications that may increase your risk of preterm labor include:
- Pre-eclampsia (hypertension)
- Placental abruption(separation from the uterus)
- Premature rupture of the membranes
- Carrying more than one baby
- Vaginal bleeding after 16 weeks, or during more than one trimester
- Infection in the cervix, uterus, vagina, or urinary tract including sexually transmitted diseases (STDs)
- Being pregnant with a single fetus after in vitro fertilization (IVF)
- Presence of a retained intrauterine device (IUD)
- Incompetent cervix
- Too much or too little fluid surrounding the baby
- Surgery on your abdomen during pregnancy
- Amniotic fluid infection
- Intrauterine fetal death
- Intrauterine growth delay
- Birth defects in the baby
Other factors associated with an increased chance of preterm labor include:
- History of 1 or more spontaneous second-trimester miscarriages
- Less than 6 months between giving birth and the beginning of the next pregnancy
- A previous preterm birth
- Uterine fibroids
- Abnormally shaped uterus
- Previous weight reduction surgery
- Procedures to remove abnormal cervical cells
Symptoms may include:
- Abdominal pain that feels something like menstrual cramps
- Dull pain in the lower back
- Pressure in the pelvis and tightening in the thighs
- Vaginal bleeding or spotting, or watery discharge
You will be asked about your symptoms and medical history. A physical exam will be done. Your doctor may recommend tests to check your cervix and membranes have ruptured. An ultrasound will help your doctor see internal structures and the baby.
Fluids in the cervix will also be tested for sign of labor progression. A tocometer may be placed to help monitor contractions.
Treatment will depend on your baby's development, especially the growth of the lungs. If your doctor believes the baby is ready, the labor may be allowed to continue. If the baby is not ready to be delivered, your doctor may try to stop the labor. Stopping labor is a complicated process and may not always work.
Some treatment options may include:
- Tocolytics—may delay labor for a few days
- Corticosteroids—to help the baby's lungs develop
- Antibiotics—if an infection is suspected or present
To help reduce your chance of preterm labor:
- Get the proper prenatal care throughout your entire pregnancy.
- Eat a healthy, balanced diet with plenty of fruits, vegetables, and whole grains.
- Consider adding fish to your diet. It may reduce the risk of preterm birth.
- Drink plenty of water.
- Avoid smoking, alcohol, and drugs.
- Keep chronic diseases under control.
- Stay active during your pregnancy. Your doctor can give you exercise guidelines that are right for you.
- If you are at high-risk for premature birth, talk to your doctor about progesterone therapy or cervical cerclage, a procedure that closes the cervix with sutures.
American Congress of Obstetricians and Gynecologists
American Pregnancy Association
Canadian Women's Health Network
The Society of Obstetricians and Gynaecologists of Canada
The American Congress of Obstetricians and Gynecologists. Management of stillbirth. Practice Bulletin. March 2009;102. Reaffirmed 2014.
Hall R. Prevention of premature birth: Do pediatricians have a role? Pediatrics. 2000;105(5):1137-1140.
Premature labor. American Pregnancy Association website. Available at: http://americanpregnancy.org/labor-and-birth/premature-labor. Updated August 2015. Accessed March 14, 2016
Preterm labor. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated February 8, 2016. Accessed March 14, 2016.
Prevention of preterm labor and preterm birth. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated November 3, 2015. Accessed March 14, 2016.
10/29/2008 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Bakhireva LN, Schatz M, et al. Asthma control during pregnancy and the risk of preterm delivery or impaired fetal growth. Ann Allergy Asthma Immunol. 2008;101:137-143.
7/6/2009 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Kumar A, Devi SG, et al. Calcium supplementation for the prevention of pre-eclampsia. Int J Gynaecol Obstet. 2009;104:32-36.
1/22/2010 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Calderon-Margalit R, Qiu C, et al. Risk of preterm delivery and other adverse perinatal outcomes in relation to maternal use of psychotropic medications during pregnancy. Am J Obstet Gynecol . 2009;201(6):579.e1-8.
8/23/2010 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: McDonald SD, Han Z, et al.; Knowledge Synthesis Group. Overweight and obesity in mothers and risk of preterm birth and low birth weight infants: systematic review and meta-analyses. BMJ. 2010;341:c3428.
10/25/2012 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Mori R, Ota E, et al. Zinc supplementation for improving pregnancy and infant outcome. Cochrane Database Syst Rev. 2012 Jul 11;7:CD000230.
11/19/2013 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Roos N, Neovius M, et al. Perinatal outcomes after bariatric surgery: nationwide population based matched cohort study. BMJ. 2013;347:f6460.
3/31/2014 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Englund-Ögge L, Brantsæter AL, et al. Maternal dietary patterns and preterm delivery: results from large prospective cohort study. BMJ. 2014 Mar 4;348:g1446.
4/24/2014 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Leventakou V, Roumeliotaki T, et al. Fish intake during pregnancy, fetal growth, and gestational length in 19 European birth cohort studies. Am J Clin Nutr. 2014 Mar;99(3):506-16.
4/29/2014 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Huybrechts KF, Sanghani RS, et al. Preterm birth and antidepressant medication use during pregnancy: a systematic review and meta-analysis. PLoS One. 2014 Mar 26;9(3):e92778.
6/9/2014 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Brown R, Gagnon R, et al. Cervical insufficiency and cervical cerclage. J Obstet Gynaecol Can. 2013;35(12):1115-1127.
8/5/2014 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed: Conner SN, Frey HA, et al. Loop electrosurgical excision procedure and risk of preterm birth: a systematic review and meta-analysis. Obstet Gynecol. 2014;123(4):752-761.
7/15/2016 DynaMed's Systematic Literature Surveillance. http://www.ebscohost.com/dynamed: Saccone G, Berghella V, Sarno L, et al. Celiac disease and obstetric complications: a systematic review and metaanalysis. 2016;214(2):225-234.
Last reviewed March 2016 by Marcie L. Sidman, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.