Final answer:
Preterm birth refers to infants born before 36-40 weeks of gestation, which often results in low birth weight and increased risk of death shortly after birth. In the U.S., intensive medical care is commonly needed for preterm infants to survive, especially for those with underdeveloped respiratory and nervous systems.
Step-by-step explanation:
Preterm birth is defined as infants born before full term, which is 36-40 weeks after fertilization. Infants that are born preterm are usually smaller than full-term infants because they have had less time to grow in the uterus. A major cause of low birth weight, defined as a birth weight lower than 2.5 kg (5.5 lb.), is preterm birth. Moreover, this condition significantly increases the risk of death shortly after birth, with as many as 30 percent of deaths in the first month of life occurring in preterm infants.
In the United States, the rate of preterm birth is relatively high compared to many other developed countries. Factors contributing to neonatal delivery and outcomes include the rapid adjustments the newborn must make to life outside the uterus, especially those born preterm who may have underdeveloped respiratory and nervous systems. Care for preterm infants often necessitates intensive medical intervention, such as what might be found in a neonatal intensive care unit (NICU), to aid in their development and increase their chances of survival. Fetal viability drastically improves with each week of gestation, particularly after the 26-week mark where the chances of survival exceed 90 percent with essential medical care.