A doctor or nurse-midwife considers a number of factors when deciding how to treat preterm labor. The fetus's level of maturity, mostly judged by weight and age, is one of these factors. The later a baby is born and the more a baby weighs, the better the baby's chances of surviving.

No treatment is used if a mother is less than 23 weeks or more than 34 to 36 weeks pregnant. A fetus delivered near 23 weeks into the pregnancy has little chance of survival. A baby born near 36 weeks into a pregnancy is likely to survive with little or no treatment.

Newborns weighing less than 3 lb (1361 g) are at the greatest risk of serious problems.