Preterm labor and birth

Last updated: September 21, 2022

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Preterm labor is defined as regular uterine contractions and cervical changes before 37 weeks of gestation. Preterm birth is defined as live birth between 20 0/7 weeks and 36 6/7 weeks of gestation. Risk factors for preterm birth 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.

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]

> 34 weeks' gestation

< 34 weeks' gestation

Induction of fetal lung maturity


Fetal neuroprotection

Antibiotics [2]

Antibiotics for GBS prophylaxis are recommended in preterm labor, PPROM, and when GBS infection is evident.

Pulmonary and cardiovascular


Periventricular leukomalacia (PVL)

Intraventricular hemorrhage (IVH) [15]



  • Hypothermia of prematurity [18]
    • Definition: impaired ability to produce an adequate body temperature due to a high surface area: volume ratio
    • Clinical features: body temperature < 97.7°F (< 36.5°C), lethargy, cyanosis
    • Treatment: rewarming in an incubator or radiant warmer
  • Apnea, bradycardia
  • Hypoglycemia, hyperglycemia


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. Demtse AG, Pfister RE, Nigussie AK, et al. Hypothermia in Preterm Newborns: Impact on Survival. Global Pediatric Health. 2020; 7 : p.2333794X2095765. doi: 10.1177/2333794x20957655 . | Open in Read by QxMD
  12. Skoll A, Boutin A, Bujold E, et al. No. 364-Antenatal Corticosteroid Therapy for Improving Neonatal Outcomes. Journal of Obstetrics and Gynaecology Canada. 2018; 40 (9): p.1219-1239. doi: 10.1016/j.jogc.2018.04.018 . | Open in Read by QxMD
  13. ACOG. Committee Opinion No. 713: Antenatal Corticosteroid Therapy for Fetal Maturation. Obstetrics & Gynecology. 2017; 130 (2): p.e102-e109. doi: 10.1097/aog.0000000000002237 . | Open in Read by QxMD
  14. Antenatal corticosteroids to prevent respiratory distress snydrome. Updated: February 1, 2004. Accessed: July 22, 2017.
  15. 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
  16. 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
  17. Rundell K, Panchal B. Preterm Labor: Prevention and Management.. Am Fam Physician. 2017; 95 (6): p.366-372.
  18. Magnesium Sulfate Use in Obstetrics. Updated: January 1, 2016. Accessed: July 22, 2017.
  19. 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

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