Trusted medical expertise in seconds.

Access 1,000+ clinical and preclinical articles. Find answers fast with the high-powered search feature and clinical tools.

Try free for 5 days
Evidence-based content, created and peer-reviewed by physicians. Read the disclaimer.

Preterm labor and birth

Last updated: July 12, 2021

Summarytoggle arrow icon

Preterm labor is defined as regular uterine contractions and cervical changes before 37 weeks of pregnancy. Preterm birth is defined as live birth between 20 0/7 weeks and 36 6/7 weeks of gestation. Approximately half of patients who deliver prematurely are diagnosed with preterm labor. Risk factors include a previous preterm birth, a short cervical length during pregnancy, and multiple gestation. Clinical features include early onset of contractions, premature cervical changes, or premature rupture of membranes. The diagnosis is usually clinical and can be supported by a cervical ultrasound and/or fetal fibronectin detection test. Treatment includes tocolysis, antenatal steroids to improve fetal lung maturity, and magnesium sulfate to provide fetal neuroprotection. Tocolytic agents are used to prolong pregnancy to gain time for steroids and magnesium sulfate to take effect. Complications of the preterm infant include intraventricular hemorrhage, neonatal respiratory distress syndrome, and necrotizing enterocolitis. Avoidance of modifiable risk factors, management of cervical insufficiency, and vaginal progesterone supplementation can help prevent preterm labor in certain risk groups.


  • Complications of preterm birth are the leading cause of death in children < 5 years of age worldwide. [1]
  • About half of patients who deliver prematurely are diagnosed with preterm labor. [2]
  • Preterm birth rate in the US: ∼ 12% of all live births [3][4]
  • African-American women are 50% more likely to give birth prematurely compared to white women.

Epidemiological data refers to the US, unless otherwise specified.

The exact mechanisms underlying premature labor are not well understood, but certain risk factors have been identified. [5]

Antibiotics for group B streptococcus (GBS) prophylaxis is recommended in preterm labor, preterm premature rupture of membranes, and when GBS infection is evident.

Morbidity and mortality in preterm infants increase with decreasing birth weight and gestational age.

We list the most important complications. The selection is not exhaustive.

  1. Preterm Birth Fact Sheet. Updated: November 1, 2016. Accessed: May 10, 2017.
  2. American College of Obstetricians and Gynecologists’ Committee on Practice Bulletins. Practice Bulletin No. 171: Management of Preterm Labor. Obstetrics & Gynecology. 2016; 128 (4): p.e155-e164. doi: 10.1097/aog.0000000000001711 . | Open in Read by QxMD
  3. Reproductive Health - Preterm Birth. Updated: November 10, 2016. Accessed: May 10, 2017.
  4. Carmen Giurgescu, Amelia Banks, Barbara L. Dancy, Kathleen Norr. African American Women's Views of Factors Impacting Preterm Birth. MCN: The American Journal of Maternal/Child Nursing. 2014; 38 (4): p.229-234. doi: 10.1097/nmc.0b013e318293bbbb . | Open in Read by QxMD
  5. What Are the Risk Factors for Preterm Labor and Birth?. . Accessed: July 22, 2017.
  6. Cavazos-Rehg PA, Krauss MJ, Spitznagel EL, et al. Maternal Age and Risk of Labor and Delivery Complications. Matern Child Health J. 2014; 19 (6): p.1202-1211. doi: 10.1007/s10995-014-1624-7 . | Open in Read by QxMD
  7. Norwitz ER, Caughey AB. Progesterone supplementation and the prevention of preterm birth.. Reviews in obstetrics & gynecology. 2011; 4 (2): p.60-72.
  8. Owens R. Intraventricular Hemorrhage in the Premature Neonate. Neonatal Network. 2005; 24 (3): p.55-71. doi: 10.1891/0730-0832.24.3.55 . | Open in Read by QxMD
  9. Bassan H. Ultrasonographic Features and Severity Scoring of Periventricular Hemorrhagic Infarction in Relation to Risk Factors and Outcome. Pediatrics. 2006; 117 (6): p.2111-2118. doi: 10.1542/peds.2005-1570 . | Open in Read by QxMD
  10. Hand IL, Shellhaas RA, Milla SS. Routine Neuroimaging of the Preterm Brain. Pediatrics. 2020; 146 (5): p.e2020029082. doi: 10.1542/peds.2020-029082 . | Open in Read by QxMD
  11. Antenatal corticosteroids to prevent respiratory distress snydrome. Updated: February 1, 2004. Accessed: July 22, 2017.
  12. The American College of Obstetricians and Gynecologists Committee Opinion. Antenatal Corticosteroid Therapy for Fetal Maturation. Journal of Obstetrics and Gynaecology Canada. 2003; 25 (1): p.45-48. doi: 10.1016/s1701-2163(16)31081-7 . | Open in Read by QxMD
  13. Räikkönen K, Gissler M, Kajantie E. Associations Between Maternal Antenatal Corticosteroid Treatment and Mental and Behavioral Disorders in Children. JAMA. 2020; 323 (19): p.1924. doi: 10.1001/jama.2020.3937 . | Open in Read by QxMD
  14. Haas DM, Caldwell DM, Kirkpatrick P, McIntosh JJ, Welton NJ. Tocolytic therapy for preterm delivery: systematic review and network meta-analysis. BMJ. 2012; 345 (oct09 2): p.e6226-e6226. doi: 10.1136/bmj.e6226 . | Open in Read by QxMD
  15. Magnesium Sulfate Use in Obstetrics. Updated: January 1, 2016. Accessed: July 22, 2017.
  16. Son M, Miller ES. Predicting preterm birth: Cervical length and fetal fibronectin. Semin Perinatol. 2017; 41 (8): p.445-451. doi: 10.1053/j.semperi.2017.08.002 . | Open in Read by QxMD