Preterm

Preterm, in obstetrics, describes a birth occurring before 37 completed weeks of gestation. It is categorized by gestational age as extremely preterm (<28 weeks), very preterm (28–<32 weeks), moderately preterm (32–<34 weeks), and late preterm (34–<37 weeks).

Preterm birth is multifactorial. Risk factors include a history of prior preterm birth, multiple gestation, cervical insufficiency, placental problems, genital tract infections, maternal hypertension or diabetes, obesity, smoking, substance use, low socioeconomic status, and limited access to prenatal care.

Often no single cause is identified; infections, placental dysfunction, uterine overdistension, or inflammatory processes may contribute to preterm labor.

Management aims to delay birth when possible and to prepare for the newborn. If preterm labor occurs, tocolytic therapy may slow contractions for 24–72 hours. When preterm birth is anticipated, antenatal corticosteroids are given to accelerate fetal lung maturity; magnesium sulfate may be used for fetal neuroprotection in very preterm infants. Antibiotics are used for infection or prolonged rupture of membranes as indicated.

Preterm infants face higher risks of respiratory distress syndrome, intraventricular hemorrhage, necrotizing enterocolitis, sepsis, temperature instability, and feeding difficulties. Survival improves with neonatal intensive care, but extreme prematurity carries increased risk of long-term neurodevelopmental impairment and chronic health problems.

Prevention focuses on risk assessment and interventions such as vaginal progesterone for certain high-risk pregnancies, cervical cerclage in select cases, treating infections, smoking cessation, and vaccination against influenza and other diseases; management of maternal conditions may reduce risk as well.