What is preterm birth?

Preterm birth refers to the birth of a baby before 37 weeks of pregnancy have been completed. Normally, a pregnancy lasts about 40 weeks. Preterm birth is a significant public health issue worldwide and is a leading cause of infant mortality and long-term health problems.


There are several categories of preterm birth:

  • Moderate to Late Preterm Birth: Babies born between 32 and 37 weeks of gestation.
  • Very Preterm Birth: Babies born between 28 and 32 weeks of gestation.
  • Extremely Preterm Birth: Babies born before 28 weeks of gestation.


Preterm birth can occur spontaneously, when labor starts naturally, or it can be induced by medical intervention due to maternal or fetal health concerns. Risk factors for preterm birth include:

  • Previous preterm birth: Women who have had a preterm birth in the past are at higher risk of having another preterm birth.
  • Multiple pregnancies: Twins, triplets, or more are at higher risk of preterm birth.
  • Infections: Infections of the reproductive tract or other parts of the body can increase the risk of preterm birth.
  • Chronic conditions: Chronic conditions such as high blood pressure, diabetes, and obesity can increase the risk of preterm birth.
  • Smoking, drug use, or alcohol consumption during pregnancy: These substances can increase the risk of preterm birth.
  • Poor prenatal care: Not receiving adequate prenatal care during pregnancy can increase the risk of preterm birth.


Preterm birth can have serious health consequences for the baby, including respiratory distress syndrome, jaundice, infections, feeding difficulties, and long-term developmental delays. Babies born extremely preterm are at highest risk of complications and may require intensive medical care in a neonatal intensive care unit (NICU) to survive.


What is the relationship between preterm birth and oxidative stress?

The relationship between preterm birth and oxidative stress is complex and multifactorial, involving various biological mechanisms that contribute to the initiation and progression of preterm labor and delivery. While the exact role of oxidative stress in preterm birth is still being elucidated, several lines of evidence suggest that oxidative stress may play a significant role in the pathophysiology of preterm birth:


  • Inflammation and Infection: Oxidative stress and inflammation are closely intertwined processes, with oxidative stress often triggering inflammatory responses and vice versa. In preterm birth, infections and inflammation are major contributors to the initiation of preterm labor. Oxidative stress induced by infections or inflammatory mediators can lead to damage to the fetal membranes, cervix, and uterine tissues, promoting uterine contractions and cervical ripening, which are characteristic features of preterm labor.


  • Placental Dysfunction: The placenta plays a crucial role in maintaining a healthy pregnancy, and dysfunction of the placenta has been implicated in the pathogenesis of preterm birth. Oxidative stress can impair placental function by causing oxidative damage to placental tissues, compromising blood flow to the fetus, and altering the production of hormones and other signaling molecules involved in the regulation of uterine contractions and cervical ripening.


  • Oxidative Damage to Membranes: The fetal membranes (amnion and chorion) play a key role in maintaining the integrity of the gestational sac and protecting the fetus from infection. Oxidative stress can cause damage to the fetal membranes, weakening their structure and integrity and increasing the risk of preterm rupture of membranes (PROM), which is a common precursor to preterm birth.


  • Oxidative Stress in Myometrium: The myometrium, the muscular layer of the uterus, undergoes remodeling and activation during labor, leading to coordinated uterine contractions. Oxidative stress in the myometrium can disrupt the balance between contraction-promoting and relaxation-promoting factors, leading to increased uterine contractility and premature onset of labor.


  • Antioxidant Defenses: Antioxidant enzymes and molecules play a crucial role in protecting cells and tissues from oxidative damage. Imbalances in antioxidant defenses and oxidative stress have been implicated in the pathogenesis of preterm birth. Decreased levels of antioxidants or impaired antioxidant enzyme activity may predispose pregnant women to oxidative stress-related complications, including preterm labor and birth.


Overall, oxidative stress is thought to contribute to the initiation and progression of preterm birth through its effects on inflammation, placental function, fetal membranes, myometrial contractility, and antioxidant defenses.