The birth of a fetus prior to 20 weeks is known as a miscarriage or spontaneous abortion, as survival is impossible at this point.
Labor beginning between 20 and 37 weeks is "preterm labor."
A baby born at 24 weeks gestation has about a 50 percent chance of survival.
A baby born at 26 weeks gestation has about an 80 percent chance of survival.
A baby born at 28 weeks gestation has about a 91 percent chance of survival.
For a baby born after 28 weeks and weighing more than 3 pounds, the chances of survival are even further increased.
After 32 weeks gestation, a baby has a 96 percent chance of survival and a significant decrease in the chances of suffering significant health problems. Babies born between the 34th and 36th week of pregnancy are likely to have minor developmental delays, but are not likely to experience any long-term effects.
What Kind Of Problems Do Preterm Infants Experience?
In general terms, the earlier a baby is born and the lower the birth weight, the lower the chance of survival and the higher the chance of handicap. Preterm babies suffer from a host of problems associated with immaturity of some or all of their organs and systems.
The natural mechanisms that combat infection are poorly developed, so preterm infants are particularly prone to developing infections.
Their skin is very thin and underdeveloped, with very little subcutaneous fat (the fat under the skin), so they quickly lose heat and are difficult to keep warm.
The lungs lack a substance called surfactant, which helps them expand. This causes difficulty in picking up sufficient oxygen from the atmosphere and removing carbon dioxide from the blood - a condition called respiratory distress syndrome.
The stomach may not be sufficiently developed to accept milk immediately.
The sucking reflex may not be present at birth.
The liver is immature, so jaundice is common and may be dangerous if severe.
Blood vessels supplying the brain may be particularly fragile and sensitive to damage, resulting in bleeding inside the skull. Depending on the degree of bleeding involved, this can have potentially serious long-term consequences, such as physical and mental handicaps and cerebral palsy.
Where Should Preterm Babies Be Delivered?
Ideally, babies who are born preterm should be delivered in hospitals prepared to care for their special needs with neonatal intensive care nurseries. Obstetricians and pediatricians are often able to predict, before birth, whether a baby is likely to need intensive care facilities, and, if so, the mother can be transported to that facility before delivery.
Parents who are at risk for delivering a premature baby might benefit from a visit to the NICU and a discussion with the neonatologist during pregnancy, so that the equipment and care will not be so intimidating after delivery.
How Should Preterm Babies Be Delivered?
Ideally, all normal preterm babies who are positioned with their heads down should be delivered vaginally by an experienced physician.Cesarean section may increase the risk to the mother without improving the outcome for the baby.
There is no indication for the routine use of forceps, though an episiotomy (an incision in the perineum, the area between the vagina and anus) may help to reduce the pressure on the delicate head of the preterm infant.
If complications develop, it may be necessary to deliver immediately by Cesarean section to minimize harm to the baby.
Most physicians deliver breech (bottom first) babies by Cesarean section.