Premature infants commonly require supplemental oxygen to treat complications of preterm birth. Hypoxia is a common complication of preterm birth in newborn infants. Insufficient surfactant in the lungs of preterm infants causes infant respiratory distress syndrome (IRDS). However, the relationship between caffeine, birthweight, and preterm birth is unclear. Glutamine is safe in adults and in preterm infants. Maternal medical conditions increase the risk of preterm birth. Prenatal supplementation with folic acid did not appear to reduce the risk of preterm births. Untreated yeast infections are associated with preterm birth. Supplementary levothyroxine may reduce the risk of preterm birth and possibly miscarriage. It is also in nutritional products for preterm infants. Babies with birth defects are at higher risk of being born preterm. Smoking bans are effective in decreasing preterm births. Passive smoking and/or smoking before the pregnancy influences the probability of a preterm birth. Women with celiac disease have an increased risk of the development of preterm birth. Transient tachypnea of the newborn presents with respiratory distress syndrome in the preterm child.