Preterm birth remains a major cause of newborn and infant
illness and death. If its causes were better understood and
prevention or treatment more effective, fewer babies would die
every year. For a pregnant woman, prevention of preterm birth
requires knowing the early signs of impending labor and seeking
prompt care should any occur. There is no exact physical or
physiologic point at which a fetus ceases to be premature and
becomes mature, no matter how precisely the pregnancy is dated.
All the changes that occur are gradual, especially in the latter
two-thirds of the third trimester. There are no great leaps
forward in baby behavior from one day to the next. In general,
however, 37 weeks completed gestation is considered mature. Any
labor occurring before 37 weeks is considered preterm labor and
any baby born before 37 weeks is considered preterm. Today, a
distinction is made between premature babies and preterm babies.
"Maturity" refers to how well the baby is able to function
outside the womb, with the mo